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Solute solvent interactions of mono saccharides D(−)-ribose and D(+)-xylose in aqueous trisodium citrate solutions at different temperatures
Journal of Molecular Liquids 211 (2015) 604–612
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Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq
Solute solvent interactions of mono saccharides D(−)-ribose and D(+)-xylose in aqueous trisodium citrate solutions at different temperatures Harsh Kumar ⁎, Sheetal Department of Chemistry, Dr B R Ambedkar National institute of Technology, Jalandhar, 144011, Punjab India
a r t i c l e
i n f o
Article history: Received 25 June 2015 Received in revised form 17 July 2015 Accepted 20 July 2015 Available online 7 August 2015 Keywords: D(+)-ribose D(−)-xylose Trisodium citrate Apparent molar volume Apparent molar isentropic compression
a b s t r a c t Densities and speed of sound measurements of two mono-saccharides D(−)-ribose and D(+)-xylose have been taken in water and in aqueous trisodium citrate in concentration (0.2, 0.4, and 0.6) mol kg−1 at T = (288.15, 298.15, 308.15 and 318.15) K and atmospheric pressure. Apparent molar volumes (V ϕ), apparent molar volumes at infinite dilution (V 0ϕ) and corresponding transfer apparent molar volumes (ΔV 0ϕ), partial molar expansion coefficients (∂V0ϕ/∂T)P and their second derivative (∂2V 0ϕ/∂T2)P, isentropic compression (Kϕ,S), isentropic compression at infinite dilution (K 0ϕ,S), transfer apparent molar isentropic compression at infinite dilution (ΔK 0ϕ,S) have been calculated using experimental density and speed of sound data. The results have been discussed in terms of different types of interactions occurring in the present system. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Saccharides are the biologically important compounds having hydrophilic hydroxyl groups and also act as typical non-electrolytes. These are important class of the chemical compounds for living organism and are of considerable interest in various aspects of research and applications. Saccharides and their derivatives are widely distributed in various forms of life as essential moieties such as glycoproteins, glycolipids, nucleic acids etc. Saccharides also help in stabilizing the native confirmation of globular proteins or reduce the extent of denaturation by other reagents [1–3]. Monosaccharide is the compound of saccharide and has been regarded as a typical non-electrolyte resembling with urea [4]. Literatures provide some studies regarding the interactions between saccharides and amino acids [5–15]. The studies on the interactions of electrolytes with saccharides are important in various fields related to biology, medicine, catalysis and environment. Thermodynamic properties are useful in studying the hydration behavior of these solutes and solute–solvent interactions [16–20]. The physico-chemical properties of various saccharides in aqueous and aqueous solutions of additives have already been studied till now [21–30] but there is no availability of data regarding the study of saccharides in aqueous solutions of citrates. Citrates are biologically and industrially important organic salts which are used in food, cosmetic, chemical and pharmaceutical ⁎ Corresponding author. E-mail addresses: [email protected], [email protected] (H. Kumar).
http://dx.doi.org/10.1016/j.molliq.2015.07.051 0167-7322/© 2015 Elsevier B.V. All rights reserved.
industries as they are significantly important in many biochemical processes [31–33]. Sodium citrates are used as an anticoagulant in blood transfusion by chelating Ca2 + ions in blood and disrupting the blood clotting mechanism. Thermodynamic studies of aqueous trisodium citrate (TSC) have been carried out earlier in water [34] and with amino acids in our laboratory [35,36] but no work has been done on the study of thermodynamic properties of saccharides with citrates so far. In view of the above, our present work reports the densities and speeds of sound of D(−)-ribose and D(+)-xylose in (0.2, 0.4 and 0.6) mol ⋅ kg− 1 aqueous solutions of TSC at T = (288.15, 298.15, 308.15 and 318.15) K. Apparent molar properties and interaction parameters have been calculated from experimentally measured densities and speeds of sound values (Table 1).
2. Experimental 2.1. Materials Both the monosaccharides, D(−)-ribose and D(+)-xylose obtained from HiMedia laboratories, India with mass purities 0.99 and trisodium citrate with mass fraction purity N 0.99 was purchased from SD Fine Chem. Ltd. India. All the chemicals were used as received without any further purification.. However, all the chemicals were dried in vacuum and stored in desiccators over P2O5 for at least two days before their use.
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
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Table 1 Densities ρ and apparent molar volumes Vϕ of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
ρ × 10−3 (kg ⋅ m−3)
Vϕ × 106 (m3 ⋅ mol−1)
288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
1.004571 1.009888 1.015133 1.020263 1.025262 1.029968 1.034943 1.039519 1.043561 1.048550 1.052843 1.056897
1.002394 1.007588 1.012701 1.017706 1.022571 1.027162 1.031997 1.036453 1.040386 1.045232 1.049415 1.053368
0.999342 1.004495 1.009571 1.014539 1.019374 1.023922 1.028717 1.033135 1.037057 1.041869 1.046004 1.049957
0.995500 1.000623 1.005672 1.010618 1.015427 1.019952 1.024722 1.029143 1.033048 1.037841 1.041979 1.045878
94.92 95.05 95.18 95.32 95.44 95.57 95.69 95.82 95.96 96.12 96.25 96.39
96.29 96.41 96.56 96.70 96.84 96.97 97.10 97.23 97.37 97.54 97.66 97.80
96.82 96.95 97.09 97.23 97.36 97.50 97.64 97.77 97.89 98.05 98.19 98.30
97.29 97.42 97.56 97.68 97.81 97.95 98.09 98.19 98.30 98.46 98.58 98.72
D(−)-Ribose + 0.2 mol kg−1 trisodium citrate 0.09578 1.039550 0.19824 1.044808 0.30242 1.050026 0.39461 1.054512 0.48582 1.058849 0.59469 1.063914 0.70094 1.068717 0.79975 1.073082 0.90108 1.077429 0.99350 1.081277 1.10133 1.085697 1.19465 1.089393
1.036681 1.041758 1.046782 1.051105 1.055291 1.060157 1.064799 1.068976 1.073157 1.076869 1.081105 1.084701
1.033190 1.038251 1.043262 1.047573 1.051750 1.056607 1.061218 1.065388 1.069564 1.073269 1.077473 1.081032
1.028877 1.033778 1.038623 1.042825 1.046855 1.051573 1.056037 1.060065 1.064095 1.067672 1.071762 1.075213
95.44 95.60 95.73 95.89 96.04 96.18 96.33 96.45 96.60 96.76 96.89 97.04
97.30 97.44 97.59 97.75 97.88 98.04 98.16 98.31 98.46 98.60 98.75 98.85
97.57 97.73 97.89 98.05 98.18 98.33 98.48 98.62 98.76 98.90 99.07 99.20
99.36 99.49 99.64 99.72 99.87 100.00 100.14 100.29 100.44 100.58 100.72 100.84
D(−)-Ribose + 0.4 mol kg−1 trisodium citrate 0.10380 1.076237 0.20161 1.081030 0.30520 1.085974 0.40303 1.090514 0.50019 1.094897 0.59688 1.099147 0.69704 1.103429 0.80074 1.107751 0.89923 1.111740 1.00110 1.115758 1.09626 1.119401 1.19331 1.123051
1.072821 1.077443 1.082205 1.086578 1.090802 1.094905 1.099017 1.103162 1.107004 1.110878 1.114377 1.117848
1.068921 1.073530 1.078285 1.08266 1.086873 1.090969 1.095096 1.099254 1.103080 1.106930 1.110425 1.113900
1.064284 1.068740 1.073334 1.077551 1.081624 1.085562 1.089526 1.093537 1.097226 1.100957 1.104336 1.107675
95.79 95.94 96.09 96.23 96.39 96.54 96.70 96.85 97.00 97.15 97.30 97.42
97.48 97.65 97.81 97.95 98.10 98.24 98.41 98.57 98.71 98.85 99.00 99.15
97.80 97.97 98.11 98.23 98.39 98.52 98.66 98.81 98.96 99.12 99.27 99.41
99.51 99.65 99.78 99.92 100.06 100.22 100.38 100.51 100.66 100.79 100.93 101.08
D(−)-Ribose + 0.6 mol kg−1 trisodium citrate 0.10777 1.110076 0.21023 1.114850 0.30079 1.118956 0.40254 1.123450 0.49952 1.127603 0.59905 1.131769 0.69517 1.135661 0.79636 1.139655 0.89728 1.143527 0.99507 1.147161 1.09813 1.150904 1.19694 1.154374
1.106210 1.110805 1.114705 1.119069 1.123061 1.127029 1.130772 1.134558 1.138253 1.141728 1.145311 1.148607
1.101976 1.106556 1.110486 1.114781 1.118759 1.122724 1.126436 1.130222 1.133926 1.137404 1.140956 1.144243
1.097009 1.101494 1.105275 1.109411 1.113233 1.117054 1.120616 1.124282 1.127829 1.131145 1.134541 1.137724
96.11 96.25 96.38 96.52 96.67 96.79 96.94 97.08 97.22 97.37 97.50 97.65
97.77 97.92 98.06 98.19 98.34 98.51 98.64 98.83 98.98 99.12 99.25 99.41
98.13 98.27 98.42 98.57 98.72 98.87 99.03 99.20 99.33 99.46 99.61 99.77
99.79 99.97 100.11 100.26 100.40 100.54 100.70 100.84 100.98 101.13 101.29 101.42
D(+)-Xylose + water 0.10489 0.20059 0.29612 0.4009 0.50273 0.60248 0.70039 0.79998 0.90110 0.99991 1.09923 1.19608
1.002728 1.007763 1.012673 1.017923 1.022902 1.027675 1.032240 1.036755 1.041251 1.045535 1.049723 1.053716
0.999658 1.004645 1.009505 1.014710 1.019629 1.024344 1.028856 1.033336 1.037766 1.041999 1.046143 1.050076
0.995810 1.000760 1.005589 1.010757 1.015658 1.020336 1.024813 1.029266 1.033686 1.037878 1.041998 1.045910
94.28 94.42 94.57 94.72 94.88 95.02 95.16 95.30 95.45 95.60 95.75 95.90
95.81 95.94 96.08 96.25 96.40 96.52 96.66 96.82 96.96 97.10 97.26 97.40
96.48 96.60 96.74 96.89 97.06 97.20 97.35 97.49 97.65 97.80 97.95 98.11
97.00 97.14 97.27 97.42 97.56 97.71 97.87 98.01 98.15 98.31 98.46 98.61
1.037033 1.042127 1.047040 1.051846
1.033466 1.038473 1.043305 1.048035
1.029294 1.034280 1.039096 1.043805
94.90 95.04 95.18 95.33
96.21 96.34 96.48 96.62
97.13 97.28 97.40 97.53
97.55 97.71 97.83 97.97
D(−)-Ribose + water 0.09952 0.19898 0.29942 0.40008 0.50039 0.59718 0.70159 0.80020 0.88967 1.00245 1.10175 1.19833
1.004929 1.010099 1.015140 1.020541 1.025655 1.030553 1.035248 1.039908 1.044526 1.048926 1.053251 1.057357
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.10045 1.039851 0.20100 1.045069 0.30045 1.050103 0.40033 1.055027
318.15 K
(continued on next page)
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Table 1 (continued) a
m (mol ⋅ kg−1)
ρ × 10−3 (kg ⋅ m−3) 288.15 K
Vϕ × 106 (m3 ⋅ mol−1)
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.50235 1.059922 0.60119 1.064545 0.69365 1.068769 0.79844 1.073446 0.89866 1.077767 0.99651 1.081902 1.09611 1.085993 1.20219 1.090251
1.056625 1.061132 1.065253 1.069793 1.074024 1.078018 1.082019 1.086164
1.052749 1.057190 1.061243 1.065713 1.069898 1.073858 1.077803 1.081897
1.048499 1.052934 1.056975 1.061461 1.065650 1.069619 1.073573 1.077697
95.50 95.66 95.79 95.94 96.12 96.27 96.43 96.59
96.78 96.94 97.07 97.24 97.40 97.58 97.72 97.88
97.66 97.81 97.94 98.11 98.24 98.39 98.52 98.67
98.10 98.23 98.36 98.49 98.60 98.73 98.86 98.97
D(+)-Xylose + 0.4 mol kg−1 trisodium citrate 0.10194 1.076230 0.20273 1.081254 0.30101 1.086028 0.40001 1.090707 0.50186 1.095391 0.60302 1.099911 0.69879 1.104079 0.80226 1.108478 0.88111 1.111738 0.99781 1.116434 1.09485 1.120204 1.19578 1.124063
1.072874 1.077778 1.082427 1.086986 1.091538 1.095952 1.100016 1.104280 1.107420 1.111993 1.115669 1.119408
1.068895 1.073708 1.078278 1.082764 1.087257 1.091576 1.095571 1.099773 1.102899 1.107387 1.111037 1.114712
1.064402 1.069198 1.073747 1.078205 1.082662 1.086970 1.090929 1.095098 1.098196 1.102647 1.106235 1.109865
95.05 95.21 95.34 95.49 95.64 95.81 95.96 96.10 96.22 96.40 96.57 96.71
96.26 96.41 96.58 96.74 96.91 97.06 97.20 97.36 97.52 97.69 97.84 97.99
97.25 97.42 97.56 97.69 97.83 98.00 98.13 98.28 98.39 98.57 98.69 98.84
97.71 97.84 97.98 98.13 98.29 98.45 98.60 98.76 98.88 99.07 99.23 99.39
D(+)-Xylose + 0.6 mol kg−1 trisodium citrate 0.10238 1.109920 0.19943 1.114551 0.30470 1.119436 0.41256 1.124292 0.50382 1.128288 0.60992 1.132806 0.70239 1.136629 0.79899 1.140520 0.89582 1.144316 0.99676 1.148160 1.08907 1.151582 1.18552 1.155036
1.106119 1.110628 1.115384 1.120113 1.123999 1.128393 1.132113 1.135912 1.139593 1.143323 1.146645 1.150039
1.101806 1.106223 1.110875 1.115498 1.119299 1.123595 1.127229 1.130924 1.134503 1.138154 1.141392 1.144708
1.097078 1.101479 1.106116 1.110731 1.114509 1.118787 1.122405 1.126093 1.129698 1.133335 1.136558 1.139834
95.30 95.42 95.55 95.70 95.83 95.98 96.12 96.26 96.40 96.55 96.68 96.84
96.51 96.64 96.78 96.92 97.05 97.21 97.34 97.47 97.62 97.77 97.90 98.03
97.50 97.65 97.81 97.97 98.10 98.25 98.39 98.54 98.70 98.85 98.99 99.11
97.93 98.06 98.21 98.35 98.50 98.66 98.80 98.94 99.07 99.22 99.36 99.51
a
318.15 K
m is the molality of monosaccharides in aqueous trisodium citrate solutions.
2.2. Methods and procedures All the solutions used in the measurements have been prepared in water which was triply distilled and degassed (specific conductance b 10 − 6 S ⋅ cm − 1 ). All the weighings were done on Sartorius CPA225D electronic balance with a precision of ± 0.01 mg. The uncertainty in the concentration of solution was estimated at ± 2 × 10− 5 mol ∙ kg− 1 in calculations. Measurements of the fresh samples were made on the same day to avoid any aging effects. The density and speed of sound measurements have been performed by using an automated vibrating tube densimeter (Anton Paar DSA 5000 M) densimeter. The speed of sound is measured using a propagation time technique. The sample is sandwiched between two piezoelectric ultrasound transducers. One transducer emits sound waves through the sample filled cavity at a frequency of approximately 3 MHz; the second transducer receives those waves. Thus, the speed of sound is obtained by dividing the known distance between transmitter and receiver by the measured propagation time of the sound wave [37]. A density check or an air/water adjustment was performed at 293.15 K with triply distilled, degassed water, and with dry air at atmospheric pressure. Before each series of measurements, the densimeter was calibrated with triple distilled and degassed water, in the experimental temperature range. The density and speeds of sound values are extremely sensitive to temperature, so it was controlled to ± 1 × 10−3 K by a built-in Peltier device. The sensitivity of the instrument corresponds to a precision in density and speeds of sound measurements of ± 1 × 10− 3 kg ⋅ m− 3 and 1 × 10− 2 m ⋅ s− 1. The uncertainty of the
density and speeds of sound estimates was found to be within ± 5 × 10− 3 kg ⋅ m− 3 and ± 5 × 10− 2 m ⋅ s− 1, respectively. 3. Results and discussion 3.1. Apparent molar volume Densities of D(−)-ribose and D(+)-xylose in water and aqueous TSC solutions (0.2, 0.4 and 0.6) mol ⋅ kg− 1 at temperature T = (288.15, 298.15, 308.15 and 318.15) K have been used to estimate the apparent molar volume Vϕ from the equation: V ϕ ¼ ½M=ρ−½ðρ − ρ0 Þ=ðmρρ0 Þ
ð1Þ
where m is the molality of the solute (saccharides), ρ and ρ0 are the densities of the solution and solvent (aqueous trisodium citrate), respectively. The Vϕ values increases with increase in concentration of saccharides as well as temperature. Apparent molar volumes at infinite dilutions V 0ϕ have been obtained by least square fitting of experimental data to the equation: V ϕ ¼ V 0ϕ þ S V m
ð2Þ
where S V⁎ is the experimental slope and represents solute–solute interactions and V 0ϕ represents solute–solvent interactions. The evaluated V 0ϕ and S V⁎ values with standard errors are expressed in Table 2 which suggests that V 0ϕ values are positive for both the monosaccharides in all the studied systems indicating strong solute–solvent
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
607
Table 2 Apparent molar volumes at infinite dilution V0ϕ and slopes S⁎v of monosaccharides in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
S⁎v × 106 (m3 ⋅ kg ⋅ mol−2)
V0ϕ×106 (m3 ⋅ mol−1) 288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
318.15 K
D(−)-Ribose 0.0 0.2 0.4 0.6
94.78 ± (0.008) 95.31 ± (0.008) 95.63 ± (0.05) 95.95 ± (0.004)
96.14 ± (0.005) 97.17 ± (0.009) 97.34 ± (0.006) 97.59 ± (0.008)
96.68 ± (0.003) 97.45 ± (0.007) 97.65 ± (0.007) 97.96 ± (0.007)
97.17 ± (0.006) 99.21 ± (0.01) 99.35 ± (0.006) 99.65 ± (0.007)
1.33 ± 0.01 1.45 ± 0.01 1.51 ± 0.007 1.41 ± 0.005
1.38 ± 0.007 1.42 ± 0.01 1.52 ± 0.008 1.52 ± 0.01
1.36 ± 0.005 1.47 ± 0.009 1.46 ± 0.01 1.51 ± 0.01
1.29 ± 0.008 1.36 ± 0.01 1.45 ± 0.008 1.49 ± 0.01
D(+)-Xylose 0.0 0.2 0.4 0.6
94.13 ± (0.003) 94.72 ± (0.007) 94.89 ± (0.006) 95.12 ± (0.10)
95.65 ± (0.005) 96.02 ± (0.01) 96.10 ± (0.006) 96.34 ± (0.006)
96.30 ± (0.006) 96.98 ± (0.007) 97.11 ± (0.006) 97.35 ± (0.004)
96.84 ± (0.005) 97.44 ± (0.009) 97.52 ± (0.008) 97.77 ± (0.007)
1.48 ± 0.004 1.55 ± 0.009 1.52 ± 0.007 1.43 ± 0.01
1.47 ± 0.006 1.54 ± 0.01 1.59 ± 0.008 1.42 ± 0.008
1.49 ± 0.009 1.40 ± 0.009 1.45 ± 0.009 1.50 ± 0.006
1.47 ± 0.007 1.29 ± 0.01 1.55 ± 0.01 1.46 ± 0.009
a
m is the molality of aqueous trisodium citrate solutions.
interactions. Further the values of D(−)-ribose and D(+)-xylose are higher in TSC than in water. This behavior may be explained in the basis of following types of interactions occurring in the ternary saccharide-TSC-water system 1. Hydrophilic-ionic interactions between the –OH groups of saccharides and ions of TSC. 2. Hydrophilic-hydrophobic interactions between –OH groups of saccharides and non-polar groups of TSC. 3. Hydrophilic-hydrophobic interactions between –OH groups of saccharides/TSC and non-polar groups of TSC/saccharides. 4. Hydrophobic-hydrophobic interactions between the non-polar groups of saccharides and TSC.
increases with increase in concentration. No regular trends in values have been found with respect to rise in temperature. According to the types of interactions discussed above, only type 1 and type 2 interactions lead to positive contribution while type 3 and type 4 give negative contribution toward apparent molar transfer volume values [38]. All the positive transfer volume values found in the present system specify that hydrophilic–ionic/hydrophilic–hydrophilic interactions predominant over hydrophilic–hydrophobic/hydrophobic–hydrophobic interactions. Further, values found for D(−)-ribose are greater than D(+)-xylose. This is due to adopting different conformations in the water. D(+)xylose adopt dominant conformation in water with all hydroxyl groups at equatorial positions. D(+)-xylose fits into the structure of water better than D(−)Ribose. Therefore dehydration of D(−)-ribose molecules contribute a more positive values to volume.
Magnitude of positive values of V0ϕ for both the monosaccharides in aqueous TSC solution increases with increase in concentration of TSC. The temperature dependence of V0ϕ values can be attributed to the change in size of primary and secondary solvation layers around the hydroxyl groups of saccharide molecules and ions of TSC. As rise in temperature releases molecules of electrostricted water from secondary layer into the bulk, expanding the solution and causing larger V0ϕ values. Smaller SV⁎ values in comparison with V0ϕ values suggest weak solute–solute interactions in the studied system. On the other hand, V0ϕ values for D(−)-ribose are greater than D(+)-xylose. The factor responsible for this behavior is different conformations of these two monosaccharide molecules in water. Apparent molar volumes of transfer at infinite dilution ΔV0ϕ for both the monosaccharides from water to aqueous solutions of TSC have been calculated by using the equation: ΔV 0ϕ ¼ V 0ϕ ðin aqueous TSC solutionsÞ − V 0ϕ ðwaterÞ:
ð3Þ
The ΔV0ϕ values are summarized in Table 3 and are graphically represented in Fig. 1. All the values are found to be positive which Table 3 Partial molar volume of transfer, ΔV0ϕ of D(−)-ribose and (+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
ΔV0ϕ× 106 (m3 ⋅ mol−1) 288.15 K
298.15 K
308.15 K
318.15 K
D(−)-Ribose 0.2 0.4 0.6
0.53 0.85 1.17
1.03 1.20 1.45
0.77 0.97 1.28
2.04 2.18 2.48
D(+)-Xylose 0.2 0.4 0.6
0.59 0.76 0.99
0.37 0.45 0.69
0.68 0.81 1.05
0.6 0.68 0.93
a
m is the molality of aqueous trisodium citrate solutions.
Fig. 1. Plot of partial molar volume of transfer against molality of trisodium citrate for (a) D(−)-ribose and (b) D(+)-xylose in aqueous trisodium solutions at different temperatures [diamond, 0.2 mol ⋅ kg − 1 TSC; square, 0.4 mol ⋅ kg − 1 TSC; triangle, 0.6 mol ⋅ kg−1 TSC].
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H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
Moreover, Shahidi's equation can be used to find relationship between positive apparent molar volume of transfer values and decrease in the shrinkage volume in aqueous TSC solution:
Hepler [41] developed the general thermodynamic expression to determine capacity of solute as structure maker or structure breaker in a mixed solvent system using general thermodynamic expression
V 0ϕ ¼ V v:w þ V void þ V shrinkage
2 ∂ϕE 0 =∂T ¼ ∂ V 0ϕ =∂T2 ¼ 2 c
ð4Þ
where Vvw is the vanderwaal's volume, Vvoid is the associated void or empty volume and Vshrinkage is the shrinkage in volume caused by different solute–solvent interactions. If it is assumed that Vvw and Vvoid have the same magnitude in water as well as in aqueous TSC solutions then the decrease in Vshrinkage is the only contributor to the positive ΔV 0ϕ values. 3.2. Apparent specific volumes Apparent specific volumes of two monosaccharides in aqueous solutions of trisodium citrate have been calculated by using equation [39]: ν ϕ ¼ V ϕ =M
ð5Þ
at T = (288.15, 298.15, 308.15, and 318.15) K(data not given). νϕ values increases with increase in solute and cosolute concentration, as well as with increase in temperature. The four basic taste ranges have been defined [40] on the basis of νϕ values i.e. salt [νϕ = (b0.33 cm3 g−1)], sour [νϕ = (0.33–0.52 cm3 g−1)], sweet [νϕ = (0.52–0.71 cm3 g−1)] and bitter [νϕ = (0.71–0.93 cm3 g−1)]. The νϕ values for the studied saccharides fall within the sweet taste range (0.52–0.71) cm3 g− 1. In the present study, both the monosaccharides retain their sweet taste in aqueous trisodium citrate solutions as the νϕ values of the monosaccharides fall within the sweet taste range. 3.3. Expansion coefficient The expansion coefficient (∂V 0ϕ/∂T)P has been calculated by fitting 0 V ϕ results into the following equation: 2 V 0ϕ ¼ a þ b T − T re f þ c T −T re f
ð6Þ
where T is the temperature in kelvin; Tref = 298.15 K: a, b and c are empirical constants. The values of these constants of monosaccharides in aqueous TSC solutions along with standard deviations are reported in Table 4. Average relative deviation (ARD) was calculated with the help of experimental and theoretical values of V 0ϕ as follows:
p
ð8Þ
P
The sign of (∂ϕ0E/∂T)p determines [41,42] the tendency of a dissolved solute as structure maker or structure breaker in a solvent which suggest that positive and small negative (∂ϕ0E/∂T)p values are observed for solutes having structure making capacity, whereas negative (∂ϕ0E/∂T)p values for structure breaking solutes. The values for limiting apparent molar expansibilities ϕ0E and (∂ϕ0E/∂T)p are reported in Table 5. It is observed from the Table that the values of ϕ0E for D(−)-ribose decreases with increase in temperature in all concentrations of trisodium citrate except at 0.4 mol ∙ kg−1. The ϕ0E values for D(+)-xylose decreases with increase in temperature in all the concentrations. This behavior may occur due to packing or caging phenomenon which suggests interactions between saccharide and salt molecules. Decreasing negative values of (∂ϕ0E/∂T)p with concentration shows the structure making ability of D(−)-ribose at higher concentrations whereas all negative (∂ϕ0E/∂T)p values of D(+)-xylose at all the concentrations shows its structure breaking ability in aqueous trisodium citrate solutions. 3.4. Apparent molar isentropic compression The apparent molar isentropic compression of D(−)-ribose and D(+)-xylose at molalities (0.1 to 1.2) mol ⋅ kg−1in water and in aqueous TSC solutions (0.2, 0.4 and 0.6) mol ⋅ kg−1 at temperature T = (288.15, 298.15, 308.15 and 318.15) K have been determined with experimentally measured speed of sound values by using following equation: K ϕ;s ¼ ðMκ S =ρÞ −
κ S; 0 ρ − κ S ρ0 =mρρ0
ð9Þ
where M and m are the molar mass (kg ⋅ mol − 1) and molality (mol ⋅ kg− 1) of the solute (monosaccharide) respectively and ρ, ρ0 and κS, κS, 0 are the densities (kg ⋅ m− 3) and isentropic compressibilities of solution and solvent (trisodium citrate + water) respectively. The isentropic compressibilities can be calculated from sound velocities and densities by using the Newton–Laplace's equation κ S ¼ 1= u2 ρ
ð10Þ
where Y = V 0ϕ (apparent molar volume at infinite dilution). The values reported in Table 4 for standard errors and ARD are very small which predicts the polynomial equation very well in the present study.
where u is the speed of sound and ρ is the density of the solution. The calculated values of Kϕ, s along with speeds of sound values for D(−)-ribose and D(+)-xylose have been listed in Table 6. From this data, it is observed that values of Kϕ,s are negative at all temperature and concentration of TSC. The magnitude of negative values decreases with increase in concentration and temperature. Negative values of
Table 4 Values of a, b and c parameters for D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures.
Table 5 Limiting apparent molar expansibilities ϕ0E for D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures.
X ARD ¼ ð1=nÞ Y exptl : − Y calc : =Y exptl :
a
m (mol a × 106 (m3 ⋅ mol−1) kg−1)
ð7Þ
b × 106 c × 106 R2 (m3 ⋅ mol−1 ⋅ K−1) (m3 ⋅ mol−1 ⋅ K−2)
D(−)-Ribose 0.0 96.03 0.2 96.71 0.4 96.92 0.6 97.21
0.099 0.122 0.115 0.113
−0.00219 −0.00025 −0.00003 0.00012
0.9999 0.9999 0.9999 0.9999
D(+)-Xylose 0.0 95.54 0.2 96.04 0.4 96.16 0.6 96.40
0.113 0.112 0.109 0.109
−0.00248 −0.00208 −0.00201 −0.00200
0.9999 0.9999 0.9999 0.9999
a
m is the molality of aqueous trisodium citrate solutions.
ARD
a m (mol ⋅ kg−1)
ϕ0E × 106 (m3 ⋅ mol−1 ⋅ K−1)
(∂ϕ0E/∂T)p (m3 ⋅ mol−1 ⋅ K−2)
288.15 K
298.15 K
308.15 K
318.15 K
0.00097 0.00316 0.00285 0.00259
D(−)-Ribose 0.0 0.2 0.4 0.6
0.140 0.127 0.115 0.112
0.100 0.122 0.115 0.115
0.060 0.117 0.114 0.117
0.020 0.112 0.114 0.120
−0.004 −0.0005 −0.00005 0.00024
0.00121 0.00129 0.00045 0.00037
D(+)-Xylose 0.0 0.2 0.4 0.6
0.150 0.154 0.149 0.150
0.110 0.112 0.109 0.109
0.070 0.070 0.069 0.069
0.030 0.029 0.029 0.029
−0.004 −0.0042 −0.0040 −0.0040
a
m is the molality of aqueous trisodium citrate solutions.
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
609
Table 6 Speeds of sound u and apparent molar isentropic compression Kϕ,s of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
u (m ⋅ s−1)
Kϕ,s × 106 (m3 ⋅ mol−1 ⋅ GPa−1)
288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
318.15 K
1472.29 1477.91 1483.55 1489.12 1494.68 1499.86 1505.47 1510.76 1515.46 1521.27 1526.27 1531.26
1502.08 1507.06 1511.97 1516.93 1521.74 1526.36 1531.14 1535.73 1539.69 1544.72 1549.18 1553.54
1524.43 1528.85 1533.22 1537.61 1541.87 1545.99 1550.24 1554.25 1557.75 1562.29 1566.17 1569.82
1540.38 1544.44 1548.53 1552.55 1556.32 1560.04 1563.86 1567.47 1570.71 1574.62 1577.89 1581.29
−17.56 −17.10 −16.67 −16.17 −15.79 −15.27 −14.83 −14.44 −14.03 −13.52 −13.07 −12.71
−11.54 −11.05 −10.46 −10.11 −9.65 −9.27 −8.76 −8.39 −7.95 −7.49 −7.17 −6.88
−7.38 −6.92 −6.43 −6.09 −5.69 −5.36 −4.90 −4.53 −4.15 −3.80 −3.46 −3.12
−4.84 −4.43 −4.12 −3.77 −3.22 −2.88 −2.41 −2.07 −1.76 −1.30 −0.89 −0.60
D(−)-Ribose + 0.2 mol kg−1 trisodium citrate 0.09578 1514.65 0.19824 1520.31 0.30242 1525.96 0.39461 1530.9 0.48582 1535.72 0.59469 1541.36 0.70094 1546.77 0.79975 1551.69 0.90108 1556.59 0.99350 1560.98 1.10133 1566.12 1.19465 1570.29
1541.42 1546.37 1551.31 1555.57 1559.67 1564.57 1569.05 1573.27 1577.54 1581.26 1585.34 1588.52
1561.39 1565.47 1569.51 1572.99 1576.32 1580.25 1583.84 1587.04 1590.36 1593.12 1596.57 1598.97
1575.81 1579.48 1583.15 1586.14 1589.13 1592.38 1595.62 1598.43 1601.18 1603.37 1606.17 1608.67
−10.88 −10.41 −9.93 −9.51 −9.10 −8.63 −8.18 −7.76 −7.29 −6.86 −6.46 −6.01
−5.16 −4.76 −4.34 −3.90 −3.47 −3.07 −2.56 −2.18 −1.82 −1.44 −0.94 −0.44
−0.61 −0.19 0.25 0.66 1.07 1.48 1.97 2.44 2.81 3.25 3.59 4.09
2.25 2.83 3.24 3.76 4.14 4.71 5.11 5.55 5.99 6.50 6.88 7.14
D(−)-Ribose + 0.4 mol kg−1 trisodium citrate 0.10380 1556.24 0.20161 1561.54 0.30520 1567.02 0.40303 1572.18 0.50019 1577.05 0.59688 1582.01 0.69704 1586.91 0.80074 1591.74 0.89923 1596.35 1.00110 1601.03 1.09626 1605.22 1.19331 1609.27
1581.01 1585.74 1590.65 1595.19 1599.56 1603.82 1608.19 1612.65 1616.49 1620.49 1624.21 1627.75
1599.21 1603.53 1607.91 1611.87 1615.75 1619.33 1622.97 1626.72 1630.17 1633.43 1636.63 1639.79
1611.42 1615.33 1619.27 1622.98 1626.41 1629.79 1633.03 1636.38 1639.29 1642.17 1644.92 1647.79
−5.69 −5.32 −4.87 −4.56 −4.07 −3.78 −3.37 −2.89 −2.52 −2.15 −1.77 −1.36
−1.68 −1.25 −0.85 −0.48 −0.09 0.27 0.62 0.95 1.40 1.77 2.10 2.48
0.41 0.83 1.33 1.81 2.21 2.71 3.15 3.53 3.90 4.35 4.65 4.96
3.31 3.68 4.17 4.47 4.91 5.28 5.74 6.11 6.54 6.96 7.28 7.55
D(−)-Ribose + 0.6 mol kg−1 trisodium citrate 0.10777 1597.94 0.21023 1603.77 0.30079 1608.79 0.40254 1614.28 0.49952 1619.31 0.59905 1624.32 0.69517 1629.02 0.79636 1633.64 0.89728 1638.23 0.99507 1642.52 1.09813 1646.83 1.19694 1650.76
1620.1 1625.49 1630.07 1635.08 1639.61 1644.04 1648.33 1652.56 1656.45 1660.03 1663.72 1667.18
1635.77 1640.55 1644.62 1649.03 1652.98 1656.89 1660.47 1663.98 1667.21 1670.07 1672.85 1675.19
1646.09 1650.62 1654.38 1658.33 1662.03 1665.41 1668.78 1671.78 1674.49 1677.45 1680.01 1681.98
−3.46 −3.07 −2.69 −2.27 −1.80 −1.37 −0.94 −0.43 0.00 0.41 0.85 1.29
−0.62 −0.18 0.27 0.70 1.19 1.71 2.07 2.55 3.06 3.54 3.98 4.39
1.50 2.09 2.56 3.03 3.52 3.99 4.45 4.97 5.48 6.00 6.54 7.10
3.89 4.24 4.72 5.29 5.71 6.28 6.65 7.21 7.78 8.12 8.62 9.17
D(+)-Xylose + water 0.10489 0.20059 0.29612 0.4009 0.50273 0.60248 0.70039 0.79998 0.9011 0.99991 1.09923 1.19608
1502.53 1507.48 1512.35 1517.67 1522.68 1527.62 1532.33 1537.26 1541.75 1546.48 1550.82 1555.56
1524.98 1529.49 1533.94 1538.73 1543.32 1547.75 1551.93 1556.39 1560.72 1564.79 1568.72 1572.84
1540.91 1545.08 1549.17 1553.58 1557.76 1561.92 1565.95 1569.86 1573.71 1577.45 1581.26 1584.97
−18.58 −18.00 −17.57 −17.08 −16.64 −16.14 −15.67 −15.31 −14.84 −14.32 −13.81 −13.40
−12.96 −12.45 −11.97 −11.52 −10.98 −10.60 −10.15 −9.83 −9.23 −8.92 −8.40 −8.19
−9.34 −8.83 −8.39 −7.90 −7.44 −7.02 −6.53 −6.25 −5.86 −5.44 −4.98 −4.70
−6.73 −6.26 −5.82 −5.36 −4.90 −4.59 −4.26 −3.85 −3.42 −3.02 −2.70 −2.40
1541.85 1546.81 1551.61 1556.43
1562.01 1566.41 1570.69 1574.97
1576.31 1580.35 1584.27 1588.11
−12.39 −11.88 −11.47 −11.04
−7.08 −6.42 −5.90 −5.53
−3.10 −2.60 −2.20 −1.90
−0.74 −0.42 −0.09 0.28
D(−)-Ribose + water 0.09952 0.19898 0.29942 0.40008 0.50039 0.59718 0.70159 0.8002 0.88967 1.00245 1.10175 1.19833
1472.67 1478.11 1483.53 1489.41 1495.11 1500.56 1505.85 1511.32 1516.69 1521.76 1526.75 1531.72
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.10045 1515.11 0.20100 1520.84 0.30045 1526.46 0.40033 1532.03
(continued on next page)
610
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
Table 6 (continued) a
m (mol ⋅ kg−1)
u (m ⋅ s−1)
Kϕ,s × 106 (m3 ⋅ mol−1 ⋅ GPa−1) 298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.50235 1537.63 0.60119 1542.87 0.69365 1547.87 0.79844 1553.28 0.89866 1558.35 0.99651 1563.26 1.09611 1567.96 1.20219 1573.13
288.15 K
1561.18 1565.66 1569.78 1574.32 1578.72 1582.74 1586.84 1590.93
1579.16 1583.07 1586.56 1590.44 1594.27 1597.97 1601.53 1605.08
1591.76 1595.28 1598.62 1602.12 1605.46 1608.76 1611.46 1614.72
−10.58 −10.05 −9.73 −9.24 −8.75 −8.33 −7.80 −7.39
−5.05 −4.57 −4.17 −3.69 −3.33 −2.87 −2.48 −2.01
−1.48 −1.02 −0.56 −0.07 0.24 0.54 0.89 1.32
0.82 1.23 1.51 1.95 2.29 2.58 3.12 3.45
D(+)-Xylose + 0.4 mol kg−1 trisodium citrate 0.10194 1556.48 0.20273 1562.32 0.30101 1567.99 0.40001 1573.66 0.50186 1579.52 0.60302 1585.23 0.69879 1590.72 0.80226 1596.42 0.88111 1600.81 0.99781 1607.24 1.09485 1612.51 1.19578 1618.21
1581.22 1586.49 1591.59 1596.68 1601.82 1606.86 1611.67 1616.72 1620.59 1626.35 1631.33 1636.15
1599.09 1603.62 1608.03 1612.46 1616.89 1621.42 1625.45 1630.01 1633.38 1638.32 1642.51 1646.76
1611.32 1615.39 1619.38 1623.34 1627.44 1631.49 1635.31 1639.34 1642.39 1647.08 1650.88 1654.84
−7.82 −7.51 −7.27 −7.00 −6.78 −6.49 −6.31 −6.01 −5.82 −5.53 −5.27 −5.12
−3.92 −3.68 −3.43 −3.17 −2.85 −2.57 −2.36 −2.07 −1.86 −1.64 −1.53 −1.30
0.16 0.34 0.50 0.65 0.90 1.04 1.31 1.44 1.59 1.82 1.95 2.12
2.11 2.35 2.49 2.70 2.86 3.02 3.17 3.38 3.52 3.66 3.81 3.95
D(+)-Xylose + 0.6 mol kg−1 trisodium citrate 0.10238 1597.89 0.19943 1603.62 0.30470 1609.73 0.41256 1615.79 0.50382 1620.84 0.60992 1626.50 0.70239 1631.29 0.79899 1636.18 0.89582 1640.72 0.99676 1645.49 1.08907 1649.61 1.18552 1653.76
1619.87 1625.04 1630.43 1635.82 1640.19 1645.18 1649.26 1653.25 1657.19 1661.13 1664.63 1667.83
1635.48 1639.99 1644.78 1649.39 1653.15 1657.36 1660.83 1664.36 1667.38 1670.58 1673.19 1675.61
1645.67 1649.74 1653.93 1658.07 1661.35 1665.00 1668.02 1671.09 1673.69 1676.56 1678.81 1681.23
−5.08 −4.61 −4.21 −3.73 −3.39 −2.94 −2.54 −2.15 −1.66 −1.25 −0.84 −0.40
−1.74 −1.31 −0.79 −0.35 0.06 0.48 0.91 1.40 1.84 2.29 2.67 3.16
1.16 1.75 2.18 2.72 3.14 3.60 4.02 4.42 4.99 5.44 5.91 6.42
3.28 3.72 4.23 4.67 5.12 5.59 6.00 6.38 6.89 7.28 7.73 8.10
a
308.15 K
318.15 K
m is the molality of monosaccharides in aqueous trisodium citrate solutions.
Kϕ,s may be due to hydration of saccharides. As hydrated molecules are already compressed to their maximum so, are less compressible than present in bulk water. Therefore, the compressibility of a solution is mainly due to the effect of pressure on the molecules of bulk water. The negative Kϕ,s values may be attributed to the strong interactions between hydroxyl groups of monosaccharides and ions of TSC in solution. The apparent molar isentropic compression at infinite dilution K 0ϕ,s and slopes S K⁎ can be obtained by using the method of linear regression of the following equation: K ϕ;s ¼ K 0ϕ;s þ SK m
ð11Þ
where K 0ϕ,s measures the solute–solvent interactions and SK⁎ affords
information regarding solute–solute interaction. The values of K 0ϕ,s and SK⁎ at different temperatures and concentration along with their standard errors have been listed in Table 7 From this data, it is observed that negative K 0ϕ,s values of these monosaccharides become less negative to the positive with increase in concentration and temperature. More negative values can be attributed to the stronger solute–solvent interactions at lower concentrations and temperature. In the presence of TSC, stronger attraction between TSC ions and water molecules, induce dehydration of monosaccharide molecules. Therefore at higher concentration of TSC, water molecules around monosaccharides are more compressible than that of at lower concentration, which may be responsible for lesser negative or even positive values of K 0ϕ,s at higher concentration. The temperature effect on isentropic compression
Table 7 Apparent molar Isentropic compression at infinite dilution K0ϕ,S and slopes SK⁎ of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol kg−1)
SK⁎ × 106 (m3 ⋅ mol−2 ⋅ GPa-1 ⋅ kg)
K0ϕ,S ×106 (m3 ⋅ mol−1 ⋅ GPa−1) 288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
318.15 K
D(−)-Ribose 0.0 0.2 0.4 0.6
−17.98 ± 0.02 −11.27 ± 0.01 −6.11 ± 0.02 −4.00 ± 0.02
−11.83 ± 0.05 −5.58 ± 0.03 −2.01 ± 0.02 −1.14 ± 0.02
−7.65 ± 0.04 −1.02 ± 0.02 −0.06 ± 0.06 1.00 ± 0.03
−5.24 ± 0.03 1.93 ± 0.05 2.92 ± 0.03 3.29 ± 0.04
4.44 ± 0.03 4.40 ± 0.02 3.97 ± 0.03 4.42 ± 0.03
4.27 ± 0.07 4.24 ± 0.04 3.77 ± 0.03 4.66 ± 0.03
3.85 ± 0.05 4.26 ± 0.03 4.25 ± 0.08 5.05 ± 0.03
3.93 ± 0.05 4.50 ± 0.07 3.97 ± 0.04 4.70 ± 0.05
D(+)-Xylose 0.0 0.2 0.4 0.6
−18.99 ± 0.03 −12.8 3 ± 0.02 −8.02 ± 0.02 −5.52 ± 0.02
−13.30 ± 0.05 −7.34 ± 0.05 −4.13 ± 0.05 −2.20 ± 0.02
−9.64 ± 0.05 −3.44 ± 0.05 −0.04 ± 0.02 0.73 ± 0.03
−7.01 ± 0.05 −1.18 ± 0.04 2.00 ± 0.02 2.85 ± 0.02
4.67 ± 0.04 4.54 ± 0.03 2.48 ± 0.03 4.28 ± 0.03
4.41 ± 0.07 4.49 ± 0.07 2.46 ± 0.06 4.49 ± 0.03
4.23 ± 0.07 4.02 ± 0.07 1.83 ± 0.03 4.74 ± 0.04
3.94 ± 0.06 3.87 ± 0.05 1.67 ± 0.03 4.47 ± 0.02
a
m is the molality of aqueous trisodium citrate solutions.
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
611
may be due to the thermal rupture of the water structure around monosaccharide molecules and TSC molecules, releasing more water molecules to the bulk and therefore responsible for lesser negative or positive values of K 0ϕ,s. Furthermore, K 0ϕ,s values of D(+)-xylose are more negative than D(−)-ribose at all the concentration and temperature. This is due to the conformational dominance of D(+)-xylose in water. As xylose fit well into the structure of water, contribute to the more negative 0 values of K ϕ,s than ribose. As water molecules around xylose are already compressed due to strong attractive interactions between xylose and water molecules therefore much lesser compressible as compared to ribose. These results hence point to the fact that hydrophilic–ionic/hydrophilic–hydrophilic interactions exceed hydrophilic–hydrophobic/hydrophobic–hydrophobic interactions. Relatively smaller values of the SK⁎ for the present system suggest very weak solute–solute interactions. The transfer apparent molar isentropic compressions at infinite dilutions, from water to the aqueous TSC solutions have been calculated as: ΔK 0ϕ;s ¼ K 0ϕ;s ðin aqueous trisodium citrate solutionÞ−K 0ϕ;s ðin waterÞ ð12Þ These ΔK 0ϕ,s values listed in the Table 8 and are graphically represented in Fig. 2 are all positive for both the monosaccharides at all concentrations and temperature. The positive values of ΔK 0ϕ,s indicate dominance of interactions between ions of TSC and hydrophilic sites of monosaccharides. All the positive values increase with increase in the concentration of TSC indicating strong interaction between hydrophilic sites of monosacacharides and TSC ions with increase in TSC concentration. No regular trend in values is found in values with respect to temperature. Lesser ΔK 0ϕ,s values of the D(+)-xylose than D(−)-ribose is in accordance with volumetric data that strongly support stronger interactions in D(+)-xylose–water than D(−)Ribose–water. 3.5. Pair and triplet interaction coefficients Interaction coefficients have been calculated based upon Mc-Miller and Mayer [43] theory of solutions which was further discussed by Friedmann and Krishnan [44], permits the separation of effects due to interactions between the pairs of solute molecules and those due to its interaction between more than two solute molecules. Therefore, apparent molar volume of transfer and apparent molar isentropic compression of transfer can be expressed as follow: ΔV 0ϕ ðwater to aqueous trisodium citrate solutionÞ ¼ 2 V AB mB þ 3 V ABB mB 2 þ ……
ð13Þ
ΔK 0ϕ;s ðwater to aqueous trisodium citrate solutionÞ þ 2 K AB mB ð14Þ þ3 K ABB mB 2 þ …… Table 8 0 Apparent molar isentropic compression of transfer, ΔKϕ,S of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol kg−1)
ΔK0ϕ,S× 106 (m3 ⋅ mol−1 ⋅ GPa−1) 298.15 K
D(−)-Ribose 0.2 0.4 0.6
6.71 11.87 13.98
6.25 9.82 10.69
6.63 7.71 8.64
7.17 8.16 8.53
D(+)-Xylose 0.2 0.4 0.6
6.15 10.97 13.47
5.96 9.17 11.09
6.20 9.60 10.37
5.83 9.01 9.85
m is the molality of aqueous trisodium citrate solutions.
where A denotes monosaccharide, B denotes trisodium citrate and mB is the molality of Trisodium citrate. The corresponding parameters VAB, VABB for volume and KAB, KABB for isentropic compression denotes pair and triplet interaction coefficients for studied monosaccharides respectively. These constants were calculated by fitting the ΔV 0ϕ and ΔK 0ϕ,s values to the above equation. The pair interaction coefficients, VAB are all positive and VABB are negative at all temperature and concentrations listed in Table 9. The values for triplet interaction coefficients are small. The positive values of VAB predict the pair wise interactions between solute and solvent predominant over triplet interactions. In the similar manner, pair interaction coefficients KAB corresponds to compressibility is positive for both the monosaccharides and triplet interaction coefficients KABB are negative for both of these monosaccharides at all temperatures and concentrations. This shows that interactions between saccharides and trisodium citrate are mainly pair wise. Table 9 Pair, V AB , K AB and triplet V ABB , K ABB interaction coefficients of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. VABB
KAB
KABB
D(−)-Ribose 288.15 1.38 ± 0.14 298.15 2.72 ± 0.61 308.15 1.97 ± 0.44 318.15 5.44 ± 1.34
−0.46 ± 0.17 −1.73 ± 0.77 −1.03 ± 0.56 −3.85 ± 1.69
20.18 ± 0.97 18.99 ± 0.01 18.19 ± 3.51 20.17 ± 3.63
−9.41 ± 1.23 −11.20 ± 0.02 −12.47 ± 4.42 −14.79 ± 4.57
D(+)-Xylose 288.15 1.53 ± 0.31 298.15 0.84 ± 0.29 308.15 1.74 ± 0.43 318.15 1.47 ± 0.45
−0.80 ± 0.39 −0.32 ± 0.37 −0.99 ± 0.54 −0.80 ± 0.57
18.01 ± 0.63 16.90 ± 0.95 18.84 ± 0.11 17.57 ± 0.19
−7.49 ± 0.80 −8.57 ± 1.20 −11.35 ± 0.14 −10.41 ± 0.24
T/K
288.15 K
a
Fig. 2. Plot of partial molar isentropic compression of transfer against molality of trisodium citrate for (a) D(−)-ribose and (b) D(+)-xylose in aqueous trisodium solutions at different temperatures [diamond, 0.2 mol ⋅ kg − 1 TSC; square, 0.4 mol ⋅ kg − 1 TSC; triangle, 0.6 mol ⋅ kg−1 TSC].
308.15 K
318.15 K
VAB
612
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
4. Conclusion Positive values of Vϕ, V 0ϕ and ΔV 0ϕ for both the monosaccharides, D(−)-ribose and D(+)-xylose vindicate the great solvation and strong hydrophilic–ionic interactions between the hydroxyl groups of saccharides and ions of TSC salt. Increasing values of apparent molar volumes with temperature and concentrations suggest stronger hydrophilic–ionic interactions with increase in TSC salt concentration. (∂ϕ0E/∂T)p values are argued of the structure making and breaking behavior of these monosaccharides in TSC solutions with increasing concentration of TSC. Further positive values of ΔK 0ϕ,s in the present system support volumetric data. The comparative Vϕ, V 0ϕ, ΔV 0ϕ, Kϕ, K 0ϕ,s and ΔK 0ϕ,s values of D(−)-ribose and D(+)-xylose indicate stronger hydrophilic–hydrophilic interactions for D(+)xylose than D(−)ribose. All these observations show the preeminence of hydrophilic–hydrophilic/hydrophilic–ionic interactions over hydrophilic–hydrophobic/hydrophobic–hydrophobic interactions in the present ternary system. Acknowledgments Authors are thankful to The Director and Head, Department of Chemistry, Dr B. R Ambedkar National Institute of Technology, Jalandhar for providing MHRD fellowship (Sheetal) and necessary laboratory facilities. References [1] C. Ebel, H. Eisenberg, R. Ghirlando, Biophys. J. 78 (2000) 385–393. [2] N. Jovanović, A. Bouchard, G.W. Hofland, G.J. Witkamp, D.J.A. Crommelin, W. Jiskoot, Eur. J. Pharm. Sci. 27 (2006) 336–345. [3] Y.H. Liao, M.B. Brown, G.P. Martin, Eur. J. Pharm. Biopharm. 58 (2004) 15–24. [4] K. Zhuo, J. Wang, J. Zhou, J. Lu, J. Phys. Chem. B 101 (1997) 3447–3451. [5] A. Pal, N. Chauhan, Indian J. Chem. 48A (2009) 1069–1077. [6] P.P. Misra, N. Kishore, J. Chem. Thermodyn. 54 (2012) 453–463. [7] S. Chauhan, K. Kumar, J. Mol. Liq. 194 (2014) 212–226.
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Solute solvent interactions of mono saccharides D(−)-ribose and D(+)-xylose in aqueous trisodium citrate solutions at different temperatures Harsh Kumar ⁎, Sheetal Department of Chemistry, Dr B R Ambedkar National institute of Technology, Jalandhar, 144011, Punjab India
a r t i c l e
i n f o
Article history: Received 25 June 2015 Received in revised form 17 July 2015 Accepted 20 July 2015 Available online 7 August 2015 Keywords: D(+)-ribose D(−)-xylose Trisodium citrate Apparent molar volume Apparent molar isentropic compression
a b s t r a c t Densities and speed of sound measurements of two mono-saccharides D(−)-ribose and D(+)-xylose have been taken in water and in aqueous trisodium citrate in concentration (0.2, 0.4, and 0.6) mol kg−1 at T = (288.15, 298.15, 308.15 and 318.15) K and atmospheric pressure. Apparent molar volumes (V ϕ), apparent molar volumes at infinite dilution (V 0ϕ) and corresponding transfer apparent molar volumes (ΔV 0ϕ), partial molar expansion coefficients (∂V0ϕ/∂T)P and their second derivative (∂2V 0ϕ/∂T2)P, isentropic compression (Kϕ,S), isentropic compression at infinite dilution (K 0ϕ,S), transfer apparent molar isentropic compression at infinite dilution (ΔK 0ϕ,S) have been calculated using experimental density and speed of sound data. The results have been discussed in terms of different types of interactions occurring in the present system. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Saccharides are the biologically important compounds having hydrophilic hydroxyl groups and also act as typical non-electrolytes. These are important class of the chemical compounds for living organism and are of considerable interest in various aspects of research and applications. Saccharides and their derivatives are widely distributed in various forms of life as essential moieties such as glycoproteins, glycolipids, nucleic acids etc. Saccharides also help in stabilizing the native confirmation of globular proteins or reduce the extent of denaturation by other reagents [1–3]. Monosaccharide is the compound of saccharide and has been regarded as a typical non-electrolyte resembling with urea [4]. Literatures provide some studies regarding the interactions between saccharides and amino acids [5–15]. The studies on the interactions of electrolytes with saccharides are important in various fields related to biology, medicine, catalysis and environment. Thermodynamic properties are useful in studying the hydration behavior of these solutes and solute–solvent interactions [16–20]. The physico-chemical properties of various saccharides in aqueous and aqueous solutions of additives have already been studied till now [21–30] but there is no availability of data regarding the study of saccharides in aqueous solutions of citrates. Citrates are biologically and industrially important organic salts which are used in food, cosmetic, chemical and pharmaceutical ⁎ Corresponding author. E-mail addresses: [email protected], [email protected] (H. Kumar).
http://dx.doi.org/10.1016/j.molliq.2015.07.051 0167-7322/© 2015 Elsevier B.V. All rights reserved.
industries as they are significantly important in many biochemical processes [31–33]. Sodium citrates are used as an anticoagulant in blood transfusion by chelating Ca2 + ions in blood and disrupting the blood clotting mechanism. Thermodynamic studies of aqueous trisodium citrate (TSC) have been carried out earlier in water [34] and with amino acids in our laboratory [35,36] but no work has been done on the study of thermodynamic properties of saccharides with citrates so far. In view of the above, our present work reports the densities and speeds of sound of D(−)-ribose and D(+)-xylose in (0.2, 0.4 and 0.6) mol ⋅ kg− 1 aqueous solutions of TSC at T = (288.15, 298.15, 308.15 and 318.15) K. Apparent molar properties and interaction parameters have been calculated from experimentally measured densities and speeds of sound values (Table 1).
2. Experimental 2.1. Materials Both the monosaccharides, D(−)-ribose and D(+)-xylose obtained from HiMedia laboratories, India with mass purities 0.99 and trisodium citrate with mass fraction purity N 0.99 was purchased from SD Fine Chem. Ltd. India. All the chemicals were used as received without any further purification.. However, all the chemicals were dried in vacuum and stored in desiccators over P2O5 for at least two days before their use.
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
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Table 1 Densities ρ and apparent molar volumes Vϕ of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
ρ × 10−3 (kg ⋅ m−3)
Vϕ × 106 (m3 ⋅ mol−1)
288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
1.004571 1.009888 1.015133 1.020263 1.025262 1.029968 1.034943 1.039519 1.043561 1.048550 1.052843 1.056897
1.002394 1.007588 1.012701 1.017706 1.022571 1.027162 1.031997 1.036453 1.040386 1.045232 1.049415 1.053368
0.999342 1.004495 1.009571 1.014539 1.019374 1.023922 1.028717 1.033135 1.037057 1.041869 1.046004 1.049957
0.995500 1.000623 1.005672 1.010618 1.015427 1.019952 1.024722 1.029143 1.033048 1.037841 1.041979 1.045878
94.92 95.05 95.18 95.32 95.44 95.57 95.69 95.82 95.96 96.12 96.25 96.39
96.29 96.41 96.56 96.70 96.84 96.97 97.10 97.23 97.37 97.54 97.66 97.80
96.82 96.95 97.09 97.23 97.36 97.50 97.64 97.77 97.89 98.05 98.19 98.30
97.29 97.42 97.56 97.68 97.81 97.95 98.09 98.19 98.30 98.46 98.58 98.72
D(−)-Ribose + 0.2 mol kg−1 trisodium citrate 0.09578 1.039550 0.19824 1.044808 0.30242 1.050026 0.39461 1.054512 0.48582 1.058849 0.59469 1.063914 0.70094 1.068717 0.79975 1.073082 0.90108 1.077429 0.99350 1.081277 1.10133 1.085697 1.19465 1.089393
1.036681 1.041758 1.046782 1.051105 1.055291 1.060157 1.064799 1.068976 1.073157 1.076869 1.081105 1.084701
1.033190 1.038251 1.043262 1.047573 1.051750 1.056607 1.061218 1.065388 1.069564 1.073269 1.077473 1.081032
1.028877 1.033778 1.038623 1.042825 1.046855 1.051573 1.056037 1.060065 1.064095 1.067672 1.071762 1.075213
95.44 95.60 95.73 95.89 96.04 96.18 96.33 96.45 96.60 96.76 96.89 97.04
97.30 97.44 97.59 97.75 97.88 98.04 98.16 98.31 98.46 98.60 98.75 98.85
97.57 97.73 97.89 98.05 98.18 98.33 98.48 98.62 98.76 98.90 99.07 99.20
99.36 99.49 99.64 99.72 99.87 100.00 100.14 100.29 100.44 100.58 100.72 100.84
D(−)-Ribose + 0.4 mol kg−1 trisodium citrate 0.10380 1.076237 0.20161 1.081030 0.30520 1.085974 0.40303 1.090514 0.50019 1.094897 0.59688 1.099147 0.69704 1.103429 0.80074 1.107751 0.89923 1.111740 1.00110 1.115758 1.09626 1.119401 1.19331 1.123051
1.072821 1.077443 1.082205 1.086578 1.090802 1.094905 1.099017 1.103162 1.107004 1.110878 1.114377 1.117848
1.068921 1.073530 1.078285 1.08266 1.086873 1.090969 1.095096 1.099254 1.103080 1.106930 1.110425 1.113900
1.064284 1.068740 1.073334 1.077551 1.081624 1.085562 1.089526 1.093537 1.097226 1.100957 1.104336 1.107675
95.79 95.94 96.09 96.23 96.39 96.54 96.70 96.85 97.00 97.15 97.30 97.42
97.48 97.65 97.81 97.95 98.10 98.24 98.41 98.57 98.71 98.85 99.00 99.15
97.80 97.97 98.11 98.23 98.39 98.52 98.66 98.81 98.96 99.12 99.27 99.41
99.51 99.65 99.78 99.92 100.06 100.22 100.38 100.51 100.66 100.79 100.93 101.08
D(−)-Ribose + 0.6 mol kg−1 trisodium citrate 0.10777 1.110076 0.21023 1.114850 0.30079 1.118956 0.40254 1.123450 0.49952 1.127603 0.59905 1.131769 0.69517 1.135661 0.79636 1.139655 0.89728 1.143527 0.99507 1.147161 1.09813 1.150904 1.19694 1.154374
1.106210 1.110805 1.114705 1.119069 1.123061 1.127029 1.130772 1.134558 1.138253 1.141728 1.145311 1.148607
1.101976 1.106556 1.110486 1.114781 1.118759 1.122724 1.126436 1.130222 1.133926 1.137404 1.140956 1.144243
1.097009 1.101494 1.105275 1.109411 1.113233 1.117054 1.120616 1.124282 1.127829 1.131145 1.134541 1.137724
96.11 96.25 96.38 96.52 96.67 96.79 96.94 97.08 97.22 97.37 97.50 97.65
97.77 97.92 98.06 98.19 98.34 98.51 98.64 98.83 98.98 99.12 99.25 99.41
98.13 98.27 98.42 98.57 98.72 98.87 99.03 99.20 99.33 99.46 99.61 99.77
99.79 99.97 100.11 100.26 100.40 100.54 100.70 100.84 100.98 101.13 101.29 101.42
D(+)-Xylose + water 0.10489 0.20059 0.29612 0.4009 0.50273 0.60248 0.70039 0.79998 0.90110 0.99991 1.09923 1.19608
1.002728 1.007763 1.012673 1.017923 1.022902 1.027675 1.032240 1.036755 1.041251 1.045535 1.049723 1.053716
0.999658 1.004645 1.009505 1.014710 1.019629 1.024344 1.028856 1.033336 1.037766 1.041999 1.046143 1.050076
0.995810 1.000760 1.005589 1.010757 1.015658 1.020336 1.024813 1.029266 1.033686 1.037878 1.041998 1.045910
94.28 94.42 94.57 94.72 94.88 95.02 95.16 95.30 95.45 95.60 95.75 95.90
95.81 95.94 96.08 96.25 96.40 96.52 96.66 96.82 96.96 97.10 97.26 97.40
96.48 96.60 96.74 96.89 97.06 97.20 97.35 97.49 97.65 97.80 97.95 98.11
97.00 97.14 97.27 97.42 97.56 97.71 97.87 98.01 98.15 98.31 98.46 98.61
1.037033 1.042127 1.047040 1.051846
1.033466 1.038473 1.043305 1.048035
1.029294 1.034280 1.039096 1.043805
94.90 95.04 95.18 95.33
96.21 96.34 96.48 96.62
97.13 97.28 97.40 97.53
97.55 97.71 97.83 97.97
D(−)-Ribose + water 0.09952 0.19898 0.29942 0.40008 0.50039 0.59718 0.70159 0.80020 0.88967 1.00245 1.10175 1.19833
1.004929 1.010099 1.015140 1.020541 1.025655 1.030553 1.035248 1.039908 1.044526 1.048926 1.053251 1.057357
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.10045 1.039851 0.20100 1.045069 0.30045 1.050103 0.40033 1.055027
318.15 K
(continued on next page)
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H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
Table 1 (continued) a
m (mol ⋅ kg−1)
ρ × 10−3 (kg ⋅ m−3) 288.15 K
Vϕ × 106 (m3 ⋅ mol−1)
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.50235 1.059922 0.60119 1.064545 0.69365 1.068769 0.79844 1.073446 0.89866 1.077767 0.99651 1.081902 1.09611 1.085993 1.20219 1.090251
1.056625 1.061132 1.065253 1.069793 1.074024 1.078018 1.082019 1.086164
1.052749 1.057190 1.061243 1.065713 1.069898 1.073858 1.077803 1.081897
1.048499 1.052934 1.056975 1.061461 1.065650 1.069619 1.073573 1.077697
95.50 95.66 95.79 95.94 96.12 96.27 96.43 96.59
96.78 96.94 97.07 97.24 97.40 97.58 97.72 97.88
97.66 97.81 97.94 98.11 98.24 98.39 98.52 98.67
98.10 98.23 98.36 98.49 98.60 98.73 98.86 98.97
D(+)-Xylose + 0.4 mol kg−1 trisodium citrate 0.10194 1.076230 0.20273 1.081254 0.30101 1.086028 0.40001 1.090707 0.50186 1.095391 0.60302 1.099911 0.69879 1.104079 0.80226 1.108478 0.88111 1.111738 0.99781 1.116434 1.09485 1.120204 1.19578 1.124063
1.072874 1.077778 1.082427 1.086986 1.091538 1.095952 1.100016 1.104280 1.107420 1.111993 1.115669 1.119408
1.068895 1.073708 1.078278 1.082764 1.087257 1.091576 1.095571 1.099773 1.102899 1.107387 1.111037 1.114712
1.064402 1.069198 1.073747 1.078205 1.082662 1.086970 1.090929 1.095098 1.098196 1.102647 1.106235 1.109865
95.05 95.21 95.34 95.49 95.64 95.81 95.96 96.10 96.22 96.40 96.57 96.71
96.26 96.41 96.58 96.74 96.91 97.06 97.20 97.36 97.52 97.69 97.84 97.99
97.25 97.42 97.56 97.69 97.83 98.00 98.13 98.28 98.39 98.57 98.69 98.84
97.71 97.84 97.98 98.13 98.29 98.45 98.60 98.76 98.88 99.07 99.23 99.39
D(+)-Xylose + 0.6 mol kg−1 trisodium citrate 0.10238 1.109920 0.19943 1.114551 0.30470 1.119436 0.41256 1.124292 0.50382 1.128288 0.60992 1.132806 0.70239 1.136629 0.79899 1.140520 0.89582 1.144316 0.99676 1.148160 1.08907 1.151582 1.18552 1.155036
1.106119 1.110628 1.115384 1.120113 1.123999 1.128393 1.132113 1.135912 1.139593 1.143323 1.146645 1.150039
1.101806 1.106223 1.110875 1.115498 1.119299 1.123595 1.127229 1.130924 1.134503 1.138154 1.141392 1.144708
1.097078 1.101479 1.106116 1.110731 1.114509 1.118787 1.122405 1.126093 1.129698 1.133335 1.136558 1.139834
95.30 95.42 95.55 95.70 95.83 95.98 96.12 96.26 96.40 96.55 96.68 96.84
96.51 96.64 96.78 96.92 97.05 97.21 97.34 97.47 97.62 97.77 97.90 98.03
97.50 97.65 97.81 97.97 98.10 98.25 98.39 98.54 98.70 98.85 98.99 99.11
97.93 98.06 98.21 98.35 98.50 98.66 98.80 98.94 99.07 99.22 99.36 99.51
a
318.15 K
m is the molality of monosaccharides in aqueous trisodium citrate solutions.
2.2. Methods and procedures All the solutions used in the measurements have been prepared in water which was triply distilled and degassed (specific conductance b 10 − 6 S ⋅ cm − 1 ). All the weighings were done on Sartorius CPA225D electronic balance with a precision of ± 0.01 mg. The uncertainty in the concentration of solution was estimated at ± 2 × 10− 5 mol ∙ kg− 1 in calculations. Measurements of the fresh samples were made on the same day to avoid any aging effects. The density and speed of sound measurements have been performed by using an automated vibrating tube densimeter (Anton Paar DSA 5000 M) densimeter. The speed of sound is measured using a propagation time technique. The sample is sandwiched between two piezoelectric ultrasound transducers. One transducer emits sound waves through the sample filled cavity at a frequency of approximately 3 MHz; the second transducer receives those waves. Thus, the speed of sound is obtained by dividing the known distance between transmitter and receiver by the measured propagation time of the sound wave [37]. A density check or an air/water adjustment was performed at 293.15 K with triply distilled, degassed water, and with dry air at atmospheric pressure. Before each series of measurements, the densimeter was calibrated with triple distilled and degassed water, in the experimental temperature range. The density and speeds of sound values are extremely sensitive to temperature, so it was controlled to ± 1 × 10−3 K by a built-in Peltier device. The sensitivity of the instrument corresponds to a precision in density and speeds of sound measurements of ± 1 × 10− 3 kg ⋅ m− 3 and 1 × 10− 2 m ⋅ s− 1. The uncertainty of the
density and speeds of sound estimates was found to be within ± 5 × 10− 3 kg ⋅ m− 3 and ± 5 × 10− 2 m ⋅ s− 1, respectively. 3. Results and discussion 3.1. Apparent molar volume Densities of D(−)-ribose and D(+)-xylose in water and aqueous TSC solutions (0.2, 0.4 and 0.6) mol ⋅ kg− 1 at temperature T = (288.15, 298.15, 308.15 and 318.15) K have been used to estimate the apparent molar volume Vϕ from the equation: V ϕ ¼ ½M=ρ−½ðρ − ρ0 Þ=ðmρρ0 Þ
ð1Þ
where m is the molality of the solute (saccharides), ρ and ρ0 are the densities of the solution and solvent (aqueous trisodium citrate), respectively. The Vϕ values increases with increase in concentration of saccharides as well as temperature. Apparent molar volumes at infinite dilutions V 0ϕ have been obtained by least square fitting of experimental data to the equation: V ϕ ¼ V 0ϕ þ S V m
ð2Þ
where S V⁎ is the experimental slope and represents solute–solute interactions and V 0ϕ represents solute–solvent interactions. The evaluated V 0ϕ and S V⁎ values with standard errors are expressed in Table 2 which suggests that V 0ϕ values are positive for both the monosaccharides in all the studied systems indicating strong solute–solvent
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
607
Table 2 Apparent molar volumes at infinite dilution V0ϕ and slopes S⁎v of monosaccharides in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
S⁎v × 106 (m3 ⋅ kg ⋅ mol−2)
V0ϕ×106 (m3 ⋅ mol−1) 288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
318.15 K
D(−)-Ribose 0.0 0.2 0.4 0.6
94.78 ± (0.008) 95.31 ± (0.008) 95.63 ± (0.05) 95.95 ± (0.004)
96.14 ± (0.005) 97.17 ± (0.009) 97.34 ± (0.006) 97.59 ± (0.008)
96.68 ± (0.003) 97.45 ± (0.007) 97.65 ± (0.007) 97.96 ± (0.007)
97.17 ± (0.006) 99.21 ± (0.01) 99.35 ± (0.006) 99.65 ± (0.007)
1.33 ± 0.01 1.45 ± 0.01 1.51 ± 0.007 1.41 ± 0.005
1.38 ± 0.007 1.42 ± 0.01 1.52 ± 0.008 1.52 ± 0.01
1.36 ± 0.005 1.47 ± 0.009 1.46 ± 0.01 1.51 ± 0.01
1.29 ± 0.008 1.36 ± 0.01 1.45 ± 0.008 1.49 ± 0.01
D(+)-Xylose 0.0 0.2 0.4 0.6
94.13 ± (0.003) 94.72 ± (0.007) 94.89 ± (0.006) 95.12 ± (0.10)
95.65 ± (0.005) 96.02 ± (0.01) 96.10 ± (0.006) 96.34 ± (0.006)
96.30 ± (0.006) 96.98 ± (0.007) 97.11 ± (0.006) 97.35 ± (0.004)
96.84 ± (0.005) 97.44 ± (0.009) 97.52 ± (0.008) 97.77 ± (0.007)
1.48 ± 0.004 1.55 ± 0.009 1.52 ± 0.007 1.43 ± 0.01
1.47 ± 0.006 1.54 ± 0.01 1.59 ± 0.008 1.42 ± 0.008
1.49 ± 0.009 1.40 ± 0.009 1.45 ± 0.009 1.50 ± 0.006
1.47 ± 0.007 1.29 ± 0.01 1.55 ± 0.01 1.46 ± 0.009
a
m is the molality of aqueous trisodium citrate solutions.
interactions. Further the values of D(−)-ribose and D(+)-xylose are higher in TSC than in water. This behavior may be explained in the basis of following types of interactions occurring in the ternary saccharide-TSC-water system 1. Hydrophilic-ionic interactions between the –OH groups of saccharides and ions of TSC. 2. Hydrophilic-hydrophobic interactions between –OH groups of saccharides and non-polar groups of TSC. 3. Hydrophilic-hydrophobic interactions between –OH groups of saccharides/TSC and non-polar groups of TSC/saccharides. 4. Hydrophobic-hydrophobic interactions between the non-polar groups of saccharides and TSC.
increases with increase in concentration. No regular trends in values have been found with respect to rise in temperature. According to the types of interactions discussed above, only type 1 and type 2 interactions lead to positive contribution while type 3 and type 4 give negative contribution toward apparent molar transfer volume values [38]. All the positive transfer volume values found in the present system specify that hydrophilic–ionic/hydrophilic–hydrophilic interactions predominant over hydrophilic–hydrophobic/hydrophobic–hydrophobic interactions. Further, values found for D(−)-ribose are greater than D(+)-xylose. This is due to adopting different conformations in the water. D(+)xylose adopt dominant conformation in water with all hydroxyl groups at equatorial positions. D(+)-xylose fits into the structure of water better than D(−)Ribose. Therefore dehydration of D(−)-ribose molecules contribute a more positive values to volume.
Magnitude of positive values of V0ϕ for both the monosaccharides in aqueous TSC solution increases with increase in concentration of TSC. The temperature dependence of V0ϕ values can be attributed to the change in size of primary and secondary solvation layers around the hydroxyl groups of saccharide molecules and ions of TSC. As rise in temperature releases molecules of electrostricted water from secondary layer into the bulk, expanding the solution and causing larger V0ϕ values. Smaller SV⁎ values in comparison with V0ϕ values suggest weak solute–solute interactions in the studied system. On the other hand, V0ϕ values for D(−)-ribose are greater than D(+)-xylose. The factor responsible for this behavior is different conformations of these two monosaccharide molecules in water. Apparent molar volumes of transfer at infinite dilution ΔV0ϕ for both the monosaccharides from water to aqueous solutions of TSC have been calculated by using the equation: ΔV 0ϕ ¼ V 0ϕ ðin aqueous TSC solutionsÞ − V 0ϕ ðwaterÞ:
ð3Þ
The ΔV0ϕ values are summarized in Table 3 and are graphically represented in Fig. 1. All the values are found to be positive which Table 3 Partial molar volume of transfer, ΔV0ϕ of D(−)-ribose and (+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
ΔV0ϕ× 106 (m3 ⋅ mol−1) 288.15 K
298.15 K
308.15 K
318.15 K
D(−)-Ribose 0.2 0.4 0.6
0.53 0.85 1.17
1.03 1.20 1.45
0.77 0.97 1.28
2.04 2.18 2.48
D(+)-Xylose 0.2 0.4 0.6
0.59 0.76 0.99
0.37 0.45 0.69
0.68 0.81 1.05
0.6 0.68 0.93
a
m is the molality of aqueous trisodium citrate solutions.
Fig. 1. Plot of partial molar volume of transfer against molality of trisodium citrate for (a) D(−)-ribose and (b) D(+)-xylose in aqueous trisodium solutions at different temperatures [diamond, 0.2 mol ⋅ kg − 1 TSC; square, 0.4 mol ⋅ kg − 1 TSC; triangle, 0.6 mol ⋅ kg−1 TSC].
608
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
Moreover, Shahidi's equation can be used to find relationship between positive apparent molar volume of transfer values and decrease in the shrinkage volume in aqueous TSC solution:
Hepler [41] developed the general thermodynamic expression to determine capacity of solute as structure maker or structure breaker in a mixed solvent system using general thermodynamic expression
V 0ϕ ¼ V v:w þ V void þ V shrinkage
2 ∂ϕE 0 =∂T ¼ ∂ V 0ϕ =∂T2 ¼ 2 c
ð4Þ
where Vvw is the vanderwaal's volume, Vvoid is the associated void or empty volume and Vshrinkage is the shrinkage in volume caused by different solute–solvent interactions. If it is assumed that Vvw and Vvoid have the same magnitude in water as well as in aqueous TSC solutions then the decrease in Vshrinkage is the only contributor to the positive ΔV 0ϕ values. 3.2. Apparent specific volumes Apparent specific volumes of two monosaccharides in aqueous solutions of trisodium citrate have been calculated by using equation [39]: ν ϕ ¼ V ϕ =M
ð5Þ
at T = (288.15, 298.15, 308.15, and 318.15) K(data not given). νϕ values increases with increase in solute and cosolute concentration, as well as with increase in temperature. The four basic taste ranges have been defined [40] on the basis of νϕ values i.e. salt [νϕ = (b0.33 cm3 g−1)], sour [νϕ = (0.33–0.52 cm3 g−1)], sweet [νϕ = (0.52–0.71 cm3 g−1)] and bitter [νϕ = (0.71–0.93 cm3 g−1)]. The νϕ values for the studied saccharides fall within the sweet taste range (0.52–0.71) cm3 g− 1. In the present study, both the monosaccharides retain their sweet taste in aqueous trisodium citrate solutions as the νϕ values of the monosaccharides fall within the sweet taste range. 3.3. Expansion coefficient The expansion coefficient (∂V 0ϕ/∂T)P has been calculated by fitting 0 V ϕ results into the following equation: 2 V 0ϕ ¼ a þ b T − T re f þ c T −T re f
ð6Þ
where T is the temperature in kelvin; Tref = 298.15 K: a, b and c are empirical constants. The values of these constants of monosaccharides in aqueous TSC solutions along with standard deviations are reported in Table 4. Average relative deviation (ARD) was calculated with the help of experimental and theoretical values of V 0ϕ as follows:
p
ð8Þ
P
The sign of (∂ϕ0E/∂T)p determines [41,42] the tendency of a dissolved solute as structure maker or structure breaker in a solvent which suggest that positive and small negative (∂ϕ0E/∂T)p values are observed for solutes having structure making capacity, whereas negative (∂ϕ0E/∂T)p values for structure breaking solutes. The values for limiting apparent molar expansibilities ϕ0E and (∂ϕ0E/∂T)p are reported in Table 5. It is observed from the Table that the values of ϕ0E for D(−)-ribose decreases with increase in temperature in all concentrations of trisodium citrate except at 0.4 mol ∙ kg−1. The ϕ0E values for D(+)-xylose decreases with increase in temperature in all the concentrations. This behavior may occur due to packing or caging phenomenon which suggests interactions between saccharide and salt molecules. Decreasing negative values of (∂ϕ0E/∂T)p with concentration shows the structure making ability of D(−)-ribose at higher concentrations whereas all negative (∂ϕ0E/∂T)p values of D(+)-xylose at all the concentrations shows its structure breaking ability in aqueous trisodium citrate solutions. 3.4. Apparent molar isentropic compression The apparent molar isentropic compression of D(−)-ribose and D(+)-xylose at molalities (0.1 to 1.2) mol ⋅ kg−1in water and in aqueous TSC solutions (0.2, 0.4 and 0.6) mol ⋅ kg−1 at temperature T = (288.15, 298.15, 308.15 and 318.15) K have been determined with experimentally measured speed of sound values by using following equation: K ϕ;s ¼ ðMκ S =ρÞ −
κ S; 0 ρ − κ S ρ0 =mρρ0
ð9Þ
where M and m are the molar mass (kg ⋅ mol − 1) and molality (mol ⋅ kg− 1) of the solute (monosaccharide) respectively and ρ, ρ0 and κS, κS, 0 are the densities (kg ⋅ m− 3) and isentropic compressibilities of solution and solvent (trisodium citrate + water) respectively. The isentropic compressibilities can be calculated from sound velocities and densities by using the Newton–Laplace's equation κ S ¼ 1= u2 ρ
ð10Þ
where Y = V 0ϕ (apparent molar volume at infinite dilution). The values reported in Table 4 for standard errors and ARD are very small which predicts the polynomial equation very well in the present study.
where u is the speed of sound and ρ is the density of the solution. The calculated values of Kϕ, s along with speeds of sound values for D(−)-ribose and D(+)-xylose have been listed in Table 6. From this data, it is observed that values of Kϕ,s are negative at all temperature and concentration of TSC. The magnitude of negative values decreases with increase in concentration and temperature. Negative values of
Table 4 Values of a, b and c parameters for D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures.
Table 5 Limiting apparent molar expansibilities ϕ0E for D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures.
X ARD ¼ ð1=nÞ Y exptl : − Y calc : =Y exptl :
a
m (mol a × 106 (m3 ⋅ mol−1) kg−1)
ð7Þ
b × 106 c × 106 R2 (m3 ⋅ mol−1 ⋅ K−1) (m3 ⋅ mol−1 ⋅ K−2)
D(−)-Ribose 0.0 96.03 0.2 96.71 0.4 96.92 0.6 97.21
0.099 0.122 0.115 0.113
−0.00219 −0.00025 −0.00003 0.00012
0.9999 0.9999 0.9999 0.9999
D(+)-Xylose 0.0 95.54 0.2 96.04 0.4 96.16 0.6 96.40
0.113 0.112 0.109 0.109
−0.00248 −0.00208 −0.00201 −0.00200
0.9999 0.9999 0.9999 0.9999
a
m is the molality of aqueous trisodium citrate solutions.
ARD
a m (mol ⋅ kg−1)
ϕ0E × 106 (m3 ⋅ mol−1 ⋅ K−1)
(∂ϕ0E/∂T)p (m3 ⋅ mol−1 ⋅ K−2)
288.15 K
298.15 K
308.15 K
318.15 K
0.00097 0.00316 0.00285 0.00259
D(−)-Ribose 0.0 0.2 0.4 0.6
0.140 0.127 0.115 0.112
0.100 0.122 0.115 0.115
0.060 0.117 0.114 0.117
0.020 0.112 0.114 0.120
−0.004 −0.0005 −0.00005 0.00024
0.00121 0.00129 0.00045 0.00037
D(+)-Xylose 0.0 0.2 0.4 0.6
0.150 0.154 0.149 0.150
0.110 0.112 0.109 0.109
0.070 0.070 0.069 0.069
0.030 0.029 0.029 0.029
−0.004 −0.0042 −0.0040 −0.0040
a
m is the molality of aqueous trisodium citrate solutions.
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
609
Table 6 Speeds of sound u and apparent molar isentropic compression Kϕ,s of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol ⋅ kg−1)
u (m ⋅ s−1)
Kϕ,s × 106 (m3 ⋅ mol−1 ⋅ GPa−1)
288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
318.15 K
1472.29 1477.91 1483.55 1489.12 1494.68 1499.86 1505.47 1510.76 1515.46 1521.27 1526.27 1531.26
1502.08 1507.06 1511.97 1516.93 1521.74 1526.36 1531.14 1535.73 1539.69 1544.72 1549.18 1553.54
1524.43 1528.85 1533.22 1537.61 1541.87 1545.99 1550.24 1554.25 1557.75 1562.29 1566.17 1569.82
1540.38 1544.44 1548.53 1552.55 1556.32 1560.04 1563.86 1567.47 1570.71 1574.62 1577.89 1581.29
−17.56 −17.10 −16.67 −16.17 −15.79 −15.27 −14.83 −14.44 −14.03 −13.52 −13.07 −12.71
−11.54 −11.05 −10.46 −10.11 −9.65 −9.27 −8.76 −8.39 −7.95 −7.49 −7.17 −6.88
−7.38 −6.92 −6.43 −6.09 −5.69 −5.36 −4.90 −4.53 −4.15 −3.80 −3.46 −3.12
−4.84 −4.43 −4.12 −3.77 −3.22 −2.88 −2.41 −2.07 −1.76 −1.30 −0.89 −0.60
D(−)-Ribose + 0.2 mol kg−1 trisodium citrate 0.09578 1514.65 0.19824 1520.31 0.30242 1525.96 0.39461 1530.9 0.48582 1535.72 0.59469 1541.36 0.70094 1546.77 0.79975 1551.69 0.90108 1556.59 0.99350 1560.98 1.10133 1566.12 1.19465 1570.29
1541.42 1546.37 1551.31 1555.57 1559.67 1564.57 1569.05 1573.27 1577.54 1581.26 1585.34 1588.52
1561.39 1565.47 1569.51 1572.99 1576.32 1580.25 1583.84 1587.04 1590.36 1593.12 1596.57 1598.97
1575.81 1579.48 1583.15 1586.14 1589.13 1592.38 1595.62 1598.43 1601.18 1603.37 1606.17 1608.67
−10.88 −10.41 −9.93 −9.51 −9.10 −8.63 −8.18 −7.76 −7.29 −6.86 −6.46 −6.01
−5.16 −4.76 −4.34 −3.90 −3.47 −3.07 −2.56 −2.18 −1.82 −1.44 −0.94 −0.44
−0.61 −0.19 0.25 0.66 1.07 1.48 1.97 2.44 2.81 3.25 3.59 4.09
2.25 2.83 3.24 3.76 4.14 4.71 5.11 5.55 5.99 6.50 6.88 7.14
D(−)-Ribose + 0.4 mol kg−1 trisodium citrate 0.10380 1556.24 0.20161 1561.54 0.30520 1567.02 0.40303 1572.18 0.50019 1577.05 0.59688 1582.01 0.69704 1586.91 0.80074 1591.74 0.89923 1596.35 1.00110 1601.03 1.09626 1605.22 1.19331 1609.27
1581.01 1585.74 1590.65 1595.19 1599.56 1603.82 1608.19 1612.65 1616.49 1620.49 1624.21 1627.75
1599.21 1603.53 1607.91 1611.87 1615.75 1619.33 1622.97 1626.72 1630.17 1633.43 1636.63 1639.79
1611.42 1615.33 1619.27 1622.98 1626.41 1629.79 1633.03 1636.38 1639.29 1642.17 1644.92 1647.79
−5.69 −5.32 −4.87 −4.56 −4.07 −3.78 −3.37 −2.89 −2.52 −2.15 −1.77 −1.36
−1.68 −1.25 −0.85 −0.48 −0.09 0.27 0.62 0.95 1.40 1.77 2.10 2.48
0.41 0.83 1.33 1.81 2.21 2.71 3.15 3.53 3.90 4.35 4.65 4.96
3.31 3.68 4.17 4.47 4.91 5.28 5.74 6.11 6.54 6.96 7.28 7.55
D(−)-Ribose + 0.6 mol kg−1 trisodium citrate 0.10777 1597.94 0.21023 1603.77 0.30079 1608.79 0.40254 1614.28 0.49952 1619.31 0.59905 1624.32 0.69517 1629.02 0.79636 1633.64 0.89728 1638.23 0.99507 1642.52 1.09813 1646.83 1.19694 1650.76
1620.1 1625.49 1630.07 1635.08 1639.61 1644.04 1648.33 1652.56 1656.45 1660.03 1663.72 1667.18
1635.77 1640.55 1644.62 1649.03 1652.98 1656.89 1660.47 1663.98 1667.21 1670.07 1672.85 1675.19
1646.09 1650.62 1654.38 1658.33 1662.03 1665.41 1668.78 1671.78 1674.49 1677.45 1680.01 1681.98
−3.46 −3.07 −2.69 −2.27 −1.80 −1.37 −0.94 −0.43 0.00 0.41 0.85 1.29
−0.62 −0.18 0.27 0.70 1.19 1.71 2.07 2.55 3.06 3.54 3.98 4.39
1.50 2.09 2.56 3.03 3.52 3.99 4.45 4.97 5.48 6.00 6.54 7.10
3.89 4.24 4.72 5.29 5.71 6.28 6.65 7.21 7.78 8.12 8.62 9.17
D(+)-Xylose + water 0.10489 0.20059 0.29612 0.4009 0.50273 0.60248 0.70039 0.79998 0.9011 0.99991 1.09923 1.19608
1502.53 1507.48 1512.35 1517.67 1522.68 1527.62 1532.33 1537.26 1541.75 1546.48 1550.82 1555.56
1524.98 1529.49 1533.94 1538.73 1543.32 1547.75 1551.93 1556.39 1560.72 1564.79 1568.72 1572.84
1540.91 1545.08 1549.17 1553.58 1557.76 1561.92 1565.95 1569.86 1573.71 1577.45 1581.26 1584.97
−18.58 −18.00 −17.57 −17.08 −16.64 −16.14 −15.67 −15.31 −14.84 −14.32 −13.81 −13.40
−12.96 −12.45 −11.97 −11.52 −10.98 −10.60 −10.15 −9.83 −9.23 −8.92 −8.40 −8.19
−9.34 −8.83 −8.39 −7.90 −7.44 −7.02 −6.53 −6.25 −5.86 −5.44 −4.98 −4.70
−6.73 −6.26 −5.82 −5.36 −4.90 −4.59 −4.26 −3.85 −3.42 −3.02 −2.70 −2.40
1541.85 1546.81 1551.61 1556.43
1562.01 1566.41 1570.69 1574.97
1576.31 1580.35 1584.27 1588.11
−12.39 −11.88 −11.47 −11.04
−7.08 −6.42 −5.90 −5.53
−3.10 −2.60 −2.20 −1.90
−0.74 −0.42 −0.09 0.28
D(−)-Ribose + water 0.09952 0.19898 0.29942 0.40008 0.50039 0.59718 0.70159 0.8002 0.88967 1.00245 1.10175 1.19833
1472.67 1478.11 1483.53 1489.41 1495.11 1500.56 1505.85 1511.32 1516.69 1521.76 1526.75 1531.72
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.10045 1515.11 0.20100 1520.84 0.30045 1526.46 0.40033 1532.03
(continued on next page)
610
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
Table 6 (continued) a
m (mol ⋅ kg−1)
u (m ⋅ s−1)
Kϕ,s × 106 (m3 ⋅ mol−1 ⋅ GPa−1) 298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
D(+)-Xylose + 0.2 mol kg−1 trisodium citrate 0.50235 1537.63 0.60119 1542.87 0.69365 1547.87 0.79844 1553.28 0.89866 1558.35 0.99651 1563.26 1.09611 1567.96 1.20219 1573.13
288.15 K
1561.18 1565.66 1569.78 1574.32 1578.72 1582.74 1586.84 1590.93
1579.16 1583.07 1586.56 1590.44 1594.27 1597.97 1601.53 1605.08
1591.76 1595.28 1598.62 1602.12 1605.46 1608.76 1611.46 1614.72
−10.58 −10.05 −9.73 −9.24 −8.75 −8.33 −7.80 −7.39
−5.05 −4.57 −4.17 −3.69 −3.33 −2.87 −2.48 −2.01
−1.48 −1.02 −0.56 −0.07 0.24 0.54 0.89 1.32
0.82 1.23 1.51 1.95 2.29 2.58 3.12 3.45
D(+)-Xylose + 0.4 mol kg−1 trisodium citrate 0.10194 1556.48 0.20273 1562.32 0.30101 1567.99 0.40001 1573.66 0.50186 1579.52 0.60302 1585.23 0.69879 1590.72 0.80226 1596.42 0.88111 1600.81 0.99781 1607.24 1.09485 1612.51 1.19578 1618.21
1581.22 1586.49 1591.59 1596.68 1601.82 1606.86 1611.67 1616.72 1620.59 1626.35 1631.33 1636.15
1599.09 1603.62 1608.03 1612.46 1616.89 1621.42 1625.45 1630.01 1633.38 1638.32 1642.51 1646.76
1611.32 1615.39 1619.38 1623.34 1627.44 1631.49 1635.31 1639.34 1642.39 1647.08 1650.88 1654.84
−7.82 −7.51 −7.27 −7.00 −6.78 −6.49 −6.31 −6.01 −5.82 −5.53 −5.27 −5.12
−3.92 −3.68 −3.43 −3.17 −2.85 −2.57 −2.36 −2.07 −1.86 −1.64 −1.53 −1.30
0.16 0.34 0.50 0.65 0.90 1.04 1.31 1.44 1.59 1.82 1.95 2.12
2.11 2.35 2.49 2.70 2.86 3.02 3.17 3.38 3.52 3.66 3.81 3.95
D(+)-Xylose + 0.6 mol kg−1 trisodium citrate 0.10238 1597.89 0.19943 1603.62 0.30470 1609.73 0.41256 1615.79 0.50382 1620.84 0.60992 1626.50 0.70239 1631.29 0.79899 1636.18 0.89582 1640.72 0.99676 1645.49 1.08907 1649.61 1.18552 1653.76
1619.87 1625.04 1630.43 1635.82 1640.19 1645.18 1649.26 1653.25 1657.19 1661.13 1664.63 1667.83
1635.48 1639.99 1644.78 1649.39 1653.15 1657.36 1660.83 1664.36 1667.38 1670.58 1673.19 1675.61
1645.67 1649.74 1653.93 1658.07 1661.35 1665.00 1668.02 1671.09 1673.69 1676.56 1678.81 1681.23
−5.08 −4.61 −4.21 −3.73 −3.39 −2.94 −2.54 −2.15 −1.66 −1.25 −0.84 −0.40
−1.74 −1.31 −0.79 −0.35 0.06 0.48 0.91 1.40 1.84 2.29 2.67 3.16
1.16 1.75 2.18 2.72 3.14 3.60 4.02 4.42 4.99 5.44 5.91 6.42
3.28 3.72 4.23 4.67 5.12 5.59 6.00 6.38 6.89 7.28 7.73 8.10
a
308.15 K
318.15 K
m is the molality of monosaccharides in aqueous trisodium citrate solutions.
Kϕ,s may be due to hydration of saccharides. As hydrated molecules are already compressed to their maximum so, are less compressible than present in bulk water. Therefore, the compressibility of a solution is mainly due to the effect of pressure on the molecules of bulk water. The negative Kϕ,s values may be attributed to the strong interactions between hydroxyl groups of monosaccharides and ions of TSC in solution. The apparent molar isentropic compression at infinite dilution K 0ϕ,s and slopes S K⁎ can be obtained by using the method of linear regression of the following equation: K ϕ;s ¼ K 0ϕ;s þ SK m
ð11Þ
where K 0ϕ,s measures the solute–solvent interactions and SK⁎ affords
information regarding solute–solute interaction. The values of K 0ϕ,s and SK⁎ at different temperatures and concentration along with their standard errors have been listed in Table 7 From this data, it is observed that negative K 0ϕ,s values of these monosaccharides become less negative to the positive with increase in concentration and temperature. More negative values can be attributed to the stronger solute–solvent interactions at lower concentrations and temperature. In the presence of TSC, stronger attraction between TSC ions and water molecules, induce dehydration of monosaccharide molecules. Therefore at higher concentration of TSC, water molecules around monosaccharides are more compressible than that of at lower concentration, which may be responsible for lesser negative or even positive values of K 0ϕ,s at higher concentration. The temperature effect on isentropic compression
Table 7 Apparent molar Isentropic compression at infinite dilution K0ϕ,S and slopes SK⁎ of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol kg−1)
SK⁎ × 106 (m3 ⋅ mol−2 ⋅ GPa-1 ⋅ kg)
K0ϕ,S ×106 (m3 ⋅ mol−1 ⋅ GPa−1) 288.15 K
298.15 K
308.15 K
318.15 K
288.15 K
298.15 K
308.15 K
318.15 K
D(−)-Ribose 0.0 0.2 0.4 0.6
−17.98 ± 0.02 −11.27 ± 0.01 −6.11 ± 0.02 −4.00 ± 0.02
−11.83 ± 0.05 −5.58 ± 0.03 −2.01 ± 0.02 −1.14 ± 0.02
−7.65 ± 0.04 −1.02 ± 0.02 −0.06 ± 0.06 1.00 ± 0.03
−5.24 ± 0.03 1.93 ± 0.05 2.92 ± 0.03 3.29 ± 0.04
4.44 ± 0.03 4.40 ± 0.02 3.97 ± 0.03 4.42 ± 0.03
4.27 ± 0.07 4.24 ± 0.04 3.77 ± 0.03 4.66 ± 0.03
3.85 ± 0.05 4.26 ± 0.03 4.25 ± 0.08 5.05 ± 0.03
3.93 ± 0.05 4.50 ± 0.07 3.97 ± 0.04 4.70 ± 0.05
D(+)-Xylose 0.0 0.2 0.4 0.6
−18.99 ± 0.03 −12.8 3 ± 0.02 −8.02 ± 0.02 −5.52 ± 0.02
−13.30 ± 0.05 −7.34 ± 0.05 −4.13 ± 0.05 −2.20 ± 0.02
−9.64 ± 0.05 −3.44 ± 0.05 −0.04 ± 0.02 0.73 ± 0.03
−7.01 ± 0.05 −1.18 ± 0.04 2.00 ± 0.02 2.85 ± 0.02
4.67 ± 0.04 4.54 ± 0.03 2.48 ± 0.03 4.28 ± 0.03
4.41 ± 0.07 4.49 ± 0.07 2.46 ± 0.06 4.49 ± 0.03
4.23 ± 0.07 4.02 ± 0.07 1.83 ± 0.03 4.74 ± 0.04
3.94 ± 0.06 3.87 ± 0.05 1.67 ± 0.03 4.47 ± 0.02
a
m is the molality of aqueous trisodium citrate solutions.
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
611
may be due to the thermal rupture of the water structure around monosaccharide molecules and TSC molecules, releasing more water molecules to the bulk and therefore responsible for lesser negative or positive values of K 0ϕ,s. Furthermore, K 0ϕ,s values of D(+)-xylose are more negative than D(−)-ribose at all the concentration and temperature. This is due to the conformational dominance of D(+)-xylose in water. As xylose fit well into the structure of water, contribute to the more negative 0 values of K ϕ,s than ribose. As water molecules around xylose are already compressed due to strong attractive interactions between xylose and water molecules therefore much lesser compressible as compared to ribose. These results hence point to the fact that hydrophilic–ionic/hydrophilic–hydrophilic interactions exceed hydrophilic–hydrophobic/hydrophobic–hydrophobic interactions. Relatively smaller values of the SK⁎ for the present system suggest very weak solute–solute interactions. The transfer apparent molar isentropic compressions at infinite dilutions, from water to the aqueous TSC solutions have been calculated as: ΔK 0ϕ;s ¼ K 0ϕ;s ðin aqueous trisodium citrate solutionÞ−K 0ϕ;s ðin waterÞ ð12Þ These ΔK 0ϕ,s values listed in the Table 8 and are graphically represented in Fig. 2 are all positive for both the monosaccharides at all concentrations and temperature. The positive values of ΔK 0ϕ,s indicate dominance of interactions between ions of TSC and hydrophilic sites of monosaccharides. All the positive values increase with increase in the concentration of TSC indicating strong interaction between hydrophilic sites of monosacacharides and TSC ions with increase in TSC concentration. No regular trend in values is found in values with respect to temperature. Lesser ΔK 0ϕ,s values of the D(+)-xylose than D(−)-ribose is in accordance with volumetric data that strongly support stronger interactions in D(+)-xylose–water than D(−)Ribose–water. 3.5. Pair and triplet interaction coefficients Interaction coefficients have been calculated based upon Mc-Miller and Mayer [43] theory of solutions which was further discussed by Friedmann and Krishnan [44], permits the separation of effects due to interactions between the pairs of solute molecules and those due to its interaction between more than two solute molecules. Therefore, apparent molar volume of transfer and apparent molar isentropic compression of transfer can be expressed as follow: ΔV 0ϕ ðwater to aqueous trisodium citrate solutionÞ ¼ 2 V AB mB þ 3 V ABB mB 2 þ ……
ð13Þ
ΔK 0ϕ;s ðwater to aqueous trisodium citrate solutionÞ þ 2 K AB mB ð14Þ þ3 K ABB mB 2 þ …… Table 8 0 Apparent molar isentropic compression of transfer, ΔKϕ,S of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. a
m (mol kg−1)
ΔK0ϕ,S× 106 (m3 ⋅ mol−1 ⋅ GPa−1) 298.15 K
D(−)-Ribose 0.2 0.4 0.6
6.71 11.87 13.98
6.25 9.82 10.69
6.63 7.71 8.64
7.17 8.16 8.53
D(+)-Xylose 0.2 0.4 0.6
6.15 10.97 13.47
5.96 9.17 11.09
6.20 9.60 10.37
5.83 9.01 9.85
m is the molality of aqueous trisodium citrate solutions.
where A denotes monosaccharide, B denotes trisodium citrate and mB is the molality of Trisodium citrate. The corresponding parameters VAB, VABB for volume and KAB, KABB for isentropic compression denotes pair and triplet interaction coefficients for studied monosaccharides respectively. These constants were calculated by fitting the ΔV 0ϕ and ΔK 0ϕ,s values to the above equation. The pair interaction coefficients, VAB are all positive and VABB are negative at all temperature and concentrations listed in Table 9. The values for triplet interaction coefficients are small. The positive values of VAB predict the pair wise interactions between solute and solvent predominant over triplet interactions. In the similar manner, pair interaction coefficients KAB corresponds to compressibility is positive for both the monosaccharides and triplet interaction coefficients KABB are negative for both of these monosaccharides at all temperatures and concentrations. This shows that interactions between saccharides and trisodium citrate are mainly pair wise. Table 9 Pair, V AB , K AB and triplet V ABB , K ABB interaction coefficients of D(−)-ribose and D(+)-xylose in aqueous TSC solutions at different temperatures. VABB
KAB
KABB
D(−)-Ribose 288.15 1.38 ± 0.14 298.15 2.72 ± 0.61 308.15 1.97 ± 0.44 318.15 5.44 ± 1.34
−0.46 ± 0.17 −1.73 ± 0.77 −1.03 ± 0.56 −3.85 ± 1.69
20.18 ± 0.97 18.99 ± 0.01 18.19 ± 3.51 20.17 ± 3.63
−9.41 ± 1.23 −11.20 ± 0.02 −12.47 ± 4.42 −14.79 ± 4.57
D(+)-Xylose 288.15 1.53 ± 0.31 298.15 0.84 ± 0.29 308.15 1.74 ± 0.43 318.15 1.47 ± 0.45
−0.80 ± 0.39 −0.32 ± 0.37 −0.99 ± 0.54 −0.80 ± 0.57
18.01 ± 0.63 16.90 ± 0.95 18.84 ± 0.11 17.57 ± 0.19
−7.49 ± 0.80 −8.57 ± 1.20 −11.35 ± 0.14 −10.41 ± 0.24
T/K
288.15 K
a
Fig. 2. Plot of partial molar isentropic compression of transfer against molality of trisodium citrate for (a) D(−)-ribose and (b) D(+)-xylose in aqueous trisodium solutions at different temperatures [diamond, 0.2 mol ⋅ kg − 1 TSC; square, 0.4 mol ⋅ kg − 1 TSC; triangle, 0.6 mol ⋅ kg−1 TSC].
308.15 K
318.15 K
VAB
612
H. Kumar, Sheetal / Journal of Molecular Liquids 211 (2015) 604–612
4. Conclusion Positive values of Vϕ, V 0ϕ and ΔV 0ϕ for both the monosaccharides, D(−)-ribose and D(+)-xylose vindicate the great solvation and strong hydrophilic–ionic interactions between the hydroxyl groups of saccharides and ions of TSC salt. Increasing values of apparent molar volumes with temperature and concentrations suggest stronger hydrophilic–ionic interactions with increase in TSC salt concentration. (∂ϕ0E/∂T)p values are argued of the structure making and breaking behavior of these monosaccharides in TSC solutions with increasing concentration of TSC. Further positive values of ΔK 0ϕ,s in the present system support volumetric data. The comparative Vϕ, V 0ϕ, ΔV 0ϕ, Kϕ, K 0ϕ,s and ΔK 0ϕ,s values of D(−)-ribose and D(+)-xylose indicate stronger hydrophilic–hydrophilic interactions for D(+)xylose than D(−)ribose. All these observations show the preeminence of hydrophilic–hydrophilic/hydrophilic–ionic interactions over hydrophilic–hydrophobic/hydrophobic–hydrophobic interactions in the present ternary system. Acknowledgments Authors are thankful to The Director and Head, Department of Chemistry, Dr B. R Ambedkar National Institute of Technology, Jalandhar for providing MHRD fellowship (Sheetal) and necessary laboratory facilities. References [1] C. Ebel, H. Eisenberg, R. Ghirlando, Biophys. J. 78 (2000) 385–393. [2] N. Jovanović, A. Bouchard, G.W. Hofland, G.J. Witkamp, D.J.A. Crommelin, W. Jiskoot, Eur. J. Pharm. Sci. 27 (2006) 336–345. [3] Y.H. Liao, M.B. Brown, G.P. Martin, Eur. J. Pharm. Biopharm. 58 (2004) 15–24. [4] K. Zhuo, J. Wang, J. Zhou, J. Lu, J. Phys. Chem. B 101 (1997) 3447–3451. [5] A. Pal, N. Chauhan, Indian J. Chem. 48A (2009) 1069–1077. [6] P.P. Misra, N. Kishore, J. Chem. Thermodyn. 54 (2012) 453–463. [7] S. Chauhan, K. Kumar, J. Mol. Liq. 194 (2014) 212–226.
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