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Kinetic-catalytic determination of manganese(II) by means of succinimidedioxime
Analytica Chimica Acta, 155 (1983) 299-303 Elsevier Science Publishers B.V.. Amsterdam -Printed
in The Netherlands
Short Communication
KINETIC-CATALYTIC DETERMINATION OF MANGANESE(I1) BY MEANS OF SUCCINIMIDEDIOXIME
F. GRASES*,
R. FORTEZA,
Department ofAnalytical (Spain)
J. G. MARCH and V. CERDA
Chemistry, Faculty of Sciences, University ofPalma de Mallorca
(Received 6th June 1983)
Summary. Kinetic methods for the determination of manganese(I1) (0.2-12 and 0.58 rg 1-l) are described, based on catalysis of the autoxidation of succinimidedioxime to give a blue (695 nm) or yellow (310 nm) product. Palladium is the only significant interference.
Imidoximes are useful reagents in inorganic analysis; some of them provide highly selective and/or sensitive qualitative and quantitative tests, especially in acidic media [ 11 . The characterization and possible analytical applications of such reagents have been studied by polarography [2], potentiometry [3], spectrophotometry [4, 51 and thermometry [ 5-71. Determination of metal ions by these techniques is normally based on equilibrium methods involving chelate formation. However, considerable activity in this field makes it difficult to improve on well known methods, whereas the use of kinetic techniques based on catalytic reactions does allow new methods to be established that are more selective and sensitive than the equilibriumbased methods. Manganese(I1) has well-known catalytic activity in oxidation reactions of organic compounds. Some 30 procedures have been described to determine this ion by using its catalytic action, but all except two [8, 91 require an oxidizing agent; the most sensitive allows the determination of lo-90 pg 1-l manganese. A procedure for the determination of manganese(II), based on the catalysis of the autoxidation of succinimidedioxime (I) is developed in the present communication.
CH2-C, 1
4
N-OH
/NH
CH2-C \\
;H
-C(ioH
CH -Cc/ ‘N-OH
N-OH
( I 1
0003-2670/83/$03.00
(II)
o 1983 Elsevier Science Publishers B.V.
300
Two products with absorption maxima at 695 nm and 310 nm are formed. They allow manganese to be determined by the tangent method in the range 0.2-12 and 0.5-8 pg l-l, respectively. Experimental Reagents and solutions. Succinimidedioxime (SIDO) was synthesized as described earlier [lo] in a two-step process. Succinodiamidoxime was obtained first by mixing succinodinitrile with hydroxylamine, and transformed to succinimidedioxime by reflux heating. Stock solutions included an ethanolic 1 g 1-l solution of succinimidedioxime and a 1.8 X 10e2 M manganese(I1) sulphate solution standardized by titration with EDTA. Analytical reagentgrade ammonium iron(I1) sulphate and EDTA were dissolved in distilled water. Perchloric acid was neutralized before analysis. All solutions were thermostatted at 20°C before use. Appamtus and measurement conditions. A Beckman Acta CIII spectrophotometer, with l.Ocm cells was used. The absorbance-time curves were obtained by using a constant movement (50 s/in) of the chart paper. Procedure. In a 50-ml beaker were placed 2 ml of 0.75 g 1-l (695 nm) or 1 g 1-l (310 nm) reagent, deionized water, so that the final volume is 4 ml, the volume of cation solution necessary for the final concentration of manganese(I1) to be between 0.2 and 12 pg 1-l (695 nm) or 0.5 and 8 pg 1-l (310 nm) and 0.8 ml (695 nm) or 0.3 ml (310 nm) of 2 M sodium hydroxide. When 30 s had elapsed after adding alkali and mixing, recording the absorbancetime curve was started. From the curve obtained, the rate of reaction was calculated by the initial rate (tangent) method. The duration of each measurement was ca. 4 min. Results and discussion The colourless reagent solution in akaline media becomes blue, green and finally, very slowly, yellow and the absorption spectrum shows maxima at 695 nm and 310 nm. This reaction is accelerated by the presence of manganese(I1). This transition does not occur when an inert atmosphere replaces the air. Under the same experimental conditions, the slope of the absorbancetime curves depends on the shape of the reaction vessel, owing to the different aeration efficiencies. Effect of reaction conditions. Formation of the blue (695 nm) and yellow (310 nm) species depends on the ethanol concentration in the mixture. The influence of ethanol on the reaction rate was studied at each wavelength. The results are shown in Fig. 1. From the analytical point of view, the plateau in the curve for 695 nm is very convenient as small variations in the ethanol concentrations in this region do not influence the results. For this reason an ethanol concentration of 50% is considered optimum, at 695 nm. A concentration of 50% ethanol is also satisfactory at 310 nm even though lower concentrations would provide higher values of tan (Y, because at these concentrations, reaction is very rapid and the results are less reproducible.
301
(al
2 6 5
1
(b)
P
25
50
75 “1. Ethanol
Fig. 1. Effect of ethanol concentration on the initial rate: (a) 3.8 X 10m3M SIDO, 20 Mg POMnnJ 0.25 M NaOH, 695 nm; (h) 3.8 x 10” M SIDO, 1 pg 1-l Mn”, 0.4 M NaOH,
The effect of sodium hydroxide concentration is shown in Fig. 2. A final alkali concentration of 0.4 M was chosen as optimum for the determination at 695 nm; 0.15 M alkali was chosen at 310 nm even though higher concentrations provided larger values of tan Q, but again these were less reproducible. The effect of the concentration of succinimidedioxime is shown in Fig. 3. The plots show no region in which the order of reaction is zero, but around 2.9 X low3 M (695 nm) and 3.8 X 10W3M (310 nm) it is a minimum. These concentrations were therefore chosen for the determination of manganese. Characteristics of the methods. The absorbance-time curves were recorded at 695 nm and 310 nm for different amounts of manganese(II), using the optimum concentrations of ethanol, sodium hydroxide and succinimidedioxime. These curves were later treated by various established kinetic methods. The data obtained are shown in Table 1. At both wavelengths, the initial
(b)
(a) 4
*
3
C 0
2 1 0.2
084
a6
0.8 [NaOH]
011
0,;
63
& [Na OH]
Fig. 2. Effect of sodium hydroxide concentration on the initial rate: (a) 3.8 X lo-” M SIDO, 20 rg 1-l Mn”-, 50% ethanol, 695 nm; (b) 3.8 X lo-’ M SIDO, 1 ugl-’ Mnz+, 50% ethanol, 310 nm.
302 (b)
0
0,0-
k” 5 0,7[E 2 96 I
0.3
I
0.4
I
I
I
0.5
0.6
0.7
0.3
I
1
I
0.4
0.5
0,6
0.7
log CRlxlO~
log CRIX IO’
Fig. 3. Effect of succinimidedioxime concentration on the initial rate: (a) 20 fig 1-l Mn’+, 0.4 M NaOH, 50% ethanol, 695 nm;(b) 1 ccgl-’ MnZ+,0.15 M NaOH, 50% ethanol, 310 nm.
rate method gave the best analytical characteristics. The selectivity of the methods was tested by obtaining the absorbancetime curves for 4 pg 1-l manganese in the presence of several foreign ions under the recommended conditions. It was found that the lowest level of interferences was given by the initial rate method. At both wavelengths, 400 pg 1-l concentrations of Ca, Sr, Ba, Zn, Cd, Ni, Co(II), Pb, Cu(II), Ag, Al, Au(III), Fe(III), Cr(III), Ce(IV), Sn(IV), Se(IV), Pt(IV), V(V), Mo(VI), CN-, NO;, SOi- and Cl- were without effect; and 100 pg 1-l magnesium could be tolerated (400 E.cg 1-l in presence of 0.01 M EDTA). Tolerable levels for palladium(I1) were 4 pg 1-l (695 nm) and 25 pg 1-l (310 nm), which were raised to 400 pg 1-i in the presence of 10 mg 1-l cyanide. Of the three methods for obtaining kinetic data, the one presenting the best analytical characteristics, i.e., the smallest amount determinable, greatest precision and fewest interferences, is the initial rate method. This method is therefore recommended. Nature of the reaction. The catalytic reaction probably involves the oxidation of manganese(I1) to Mn(III), and possibly Mn(IV), by atmospheric TABLE 1 Characteristics of the kinetic procedures for manganese(I1) Method
Initial rate Fixed time Fixed absorbance
A = 310 nm
h = 695 nm Useful range (PB I-‘)
R.s.d.’ (%)
Useful range (rg I-‘)
R.s.d.a (%)
0.2-12 l-12b l-10C
2.4 8.0 6.5
0.5-8 1-6b 1-6d
2.1 7.8 4.5
aRelative deviation (n = 11). bTime = 175 s. ‘Absorbance
= 0.38. dAbsorbance
= 0.70.
303 TABLE 2 Determination
of manganese in analytical reagents
Sample
Wavelength (nm)
Reported maximum content (W)
Found (%)
Perchloric acid (Panreac GR) Ammonium iron(I1) sulphate (Merck GR) EDTA (Probus GR)
310
0.00005
0.00002
310
0.05
0.03
695
-
0.00001
oxygen in alkaline medium. The reaction steps are probably: Mn(I1) + l/2 O2 =+Mn(II1) Succinimidedioxime
+ Mn(II1) * oxidation products + Mn(I1)
The spectrum of the oxidation product shows absorption bands at 310 and 695 nm. The blue species is unstable and disappears gradually, whereas the absorbance of the yellow species increases until it becomes constant. The oxidation therefore probably involves the formation of a blue nitroso compound which yields a substance readily oxidized in basic solutions to a yellow nitro compound. This is supported by the fact that when an induction period appears under certain conditions, it is shorter for the blue form. Moreover, oxidation of maleinimidedioxime(I1) first gives a nitroso compound which already possesses aromatic character, so that a yellow product appears instantly, without detection of any blue form. Applications. To test the proposed method, it was applied to the determination of traces of manganese in analytical reagents. In all instances, the standard addition method was employed. In order to detect the existence of possible interferences, the manganese recovery was calculated by comparing the results obtained before and after the addition of the manganese standard solutions. The results obtained for the different aliquots of the prepared solutions (Table 2) indicate the sensitivity of the procedures. REFERENCES 1 2 3 4 5 6 7 8 9 10
F. Buscarons, Mem. R. Acad. Cienc. Artes Barcelona, 41 (1972) 247. C. Mongay and V. Cerda, Quim. Anal., 28 (1974) 271; 29 (1975) 166. M. L. Albelda, V. Cerda, R. Pardo and P. Sanchez-Batanero, Quim. Anal., in press. M. L. Albelda, V. Cerdd and C. Mongay, Bull. Sot. Chii. Fr., (1982) 19. J. Rius, C. Mongay and V. CerdP, Afinidad, 38 (1981) 357. J. Lumbiarres, C. Mongay and V. Cerda, AnaIusis, 8 (1980) 62; J. Thermal Anal., 22 (1981) 275. M. L. Albelda, V. Cerdl and C. Mongay, J. Thermal Anal., 24 (1982) 289. D. Perez-Bendito, M. Vaicarcel, M. Ternero and F. Pino, Anal. Chim. Acta, 94 (1977) 405. E. A. Morgen, N. A. Vlasov and L. A. Kozhemyakina, Zh. Anal. Khim., 27 (1972) 2064. F. Sembritzki, Berichte, 22 (1889) 2958.
in The Netherlands
Short Communication
KINETIC-CATALYTIC DETERMINATION OF MANGANESE(I1) BY MEANS OF SUCCINIMIDEDIOXIME
F. GRASES*,
R. FORTEZA,
Department ofAnalytical (Spain)
J. G. MARCH and V. CERDA
Chemistry, Faculty of Sciences, University ofPalma de Mallorca
(Received 6th June 1983)
Summary. Kinetic methods for the determination of manganese(I1) (0.2-12 and 0.58 rg 1-l) are described, based on catalysis of the autoxidation of succinimidedioxime to give a blue (695 nm) or yellow (310 nm) product. Palladium is the only significant interference.
Imidoximes are useful reagents in inorganic analysis; some of them provide highly selective and/or sensitive qualitative and quantitative tests, especially in acidic media [ 11 . The characterization and possible analytical applications of such reagents have been studied by polarography [2], potentiometry [3], spectrophotometry [4, 51 and thermometry [ 5-71. Determination of metal ions by these techniques is normally based on equilibrium methods involving chelate formation. However, considerable activity in this field makes it difficult to improve on well known methods, whereas the use of kinetic techniques based on catalytic reactions does allow new methods to be established that are more selective and sensitive than the equilibriumbased methods. Manganese(I1) has well-known catalytic activity in oxidation reactions of organic compounds. Some 30 procedures have been described to determine this ion by using its catalytic action, but all except two [8, 91 require an oxidizing agent; the most sensitive allows the determination of lo-90 pg 1-l manganese. A procedure for the determination of manganese(II), based on the catalysis of the autoxidation of succinimidedioxime (I) is developed in the present communication.
CH2-C, 1
4
N-OH
/NH
CH2-C \\
;H
-C(ioH
CH -Cc/ ‘N-OH
N-OH
( I 1
0003-2670/83/$03.00
(II)
o 1983 Elsevier Science Publishers B.V.
300
Two products with absorption maxima at 695 nm and 310 nm are formed. They allow manganese to be determined by the tangent method in the range 0.2-12 and 0.5-8 pg l-l, respectively. Experimental Reagents and solutions. Succinimidedioxime (SIDO) was synthesized as described earlier [lo] in a two-step process. Succinodiamidoxime was obtained first by mixing succinodinitrile with hydroxylamine, and transformed to succinimidedioxime by reflux heating. Stock solutions included an ethanolic 1 g 1-l solution of succinimidedioxime and a 1.8 X 10e2 M manganese(I1) sulphate solution standardized by titration with EDTA. Analytical reagentgrade ammonium iron(I1) sulphate and EDTA were dissolved in distilled water. Perchloric acid was neutralized before analysis. All solutions were thermostatted at 20°C before use. Appamtus and measurement conditions. A Beckman Acta CIII spectrophotometer, with l.Ocm cells was used. The absorbance-time curves were obtained by using a constant movement (50 s/in) of the chart paper. Procedure. In a 50-ml beaker were placed 2 ml of 0.75 g 1-l (695 nm) or 1 g 1-l (310 nm) reagent, deionized water, so that the final volume is 4 ml, the volume of cation solution necessary for the final concentration of manganese(I1) to be between 0.2 and 12 pg 1-l (695 nm) or 0.5 and 8 pg 1-l (310 nm) and 0.8 ml (695 nm) or 0.3 ml (310 nm) of 2 M sodium hydroxide. When 30 s had elapsed after adding alkali and mixing, recording the absorbancetime curve was started. From the curve obtained, the rate of reaction was calculated by the initial rate (tangent) method. The duration of each measurement was ca. 4 min. Results and discussion The colourless reagent solution in akaline media becomes blue, green and finally, very slowly, yellow and the absorption spectrum shows maxima at 695 nm and 310 nm. This reaction is accelerated by the presence of manganese(I1). This transition does not occur when an inert atmosphere replaces the air. Under the same experimental conditions, the slope of the absorbancetime curves depends on the shape of the reaction vessel, owing to the different aeration efficiencies. Effect of reaction conditions. Formation of the blue (695 nm) and yellow (310 nm) species depends on the ethanol concentration in the mixture. The influence of ethanol on the reaction rate was studied at each wavelength. The results are shown in Fig. 1. From the analytical point of view, the plateau in the curve for 695 nm is very convenient as small variations in the ethanol concentrations in this region do not influence the results. For this reason an ethanol concentration of 50% is considered optimum, at 695 nm. A concentration of 50% ethanol is also satisfactory at 310 nm even though lower concentrations would provide higher values of tan (Y, because at these concentrations, reaction is very rapid and the results are less reproducible.
301
(al
2 6 5
1
(b)
P
25
50
75 “1. Ethanol
Fig. 1. Effect of ethanol concentration on the initial rate: (a) 3.8 X 10m3M SIDO, 20 Mg POMnnJ 0.25 M NaOH, 695 nm; (h) 3.8 x 10” M SIDO, 1 pg 1-l Mn”, 0.4 M NaOH,
The effect of sodium hydroxide concentration is shown in Fig. 2. A final alkali concentration of 0.4 M was chosen as optimum for the determination at 695 nm; 0.15 M alkali was chosen at 310 nm even though higher concentrations provided larger values of tan Q, but again these were less reproducible. The effect of the concentration of succinimidedioxime is shown in Fig. 3. The plots show no region in which the order of reaction is zero, but around 2.9 X low3 M (695 nm) and 3.8 X 10W3M (310 nm) it is a minimum. These concentrations were therefore chosen for the determination of manganese. Characteristics of the methods. The absorbance-time curves were recorded at 695 nm and 310 nm for different amounts of manganese(II), using the optimum concentrations of ethanol, sodium hydroxide and succinimidedioxime. These curves were later treated by various established kinetic methods. The data obtained are shown in Table 1. At both wavelengths, the initial
(b)
(a) 4
*
3
C 0
2 1 0.2
084
a6
0.8 [NaOH]
011
0,;
63
& [Na OH]
Fig. 2. Effect of sodium hydroxide concentration on the initial rate: (a) 3.8 X lo-” M SIDO, 20 rg 1-l Mn”-, 50% ethanol, 695 nm; (b) 3.8 X lo-’ M SIDO, 1 ugl-’ Mnz+, 50% ethanol, 310 nm.
302 (b)
0
0,0-
k” 5 0,7[E 2 96 I
0.3
I
0.4
I
I
I
0.5
0.6
0.7
0.3
I
1
I
0.4
0.5
0,6
0.7
log CRlxlO~
log CRIX IO’
Fig. 3. Effect of succinimidedioxime concentration on the initial rate: (a) 20 fig 1-l Mn’+, 0.4 M NaOH, 50% ethanol, 695 nm;(b) 1 ccgl-’ MnZ+,0.15 M NaOH, 50% ethanol, 310 nm.
rate method gave the best analytical characteristics. The selectivity of the methods was tested by obtaining the absorbancetime curves for 4 pg 1-l manganese in the presence of several foreign ions under the recommended conditions. It was found that the lowest level of interferences was given by the initial rate method. At both wavelengths, 400 pg 1-l concentrations of Ca, Sr, Ba, Zn, Cd, Ni, Co(II), Pb, Cu(II), Ag, Al, Au(III), Fe(III), Cr(III), Ce(IV), Sn(IV), Se(IV), Pt(IV), V(V), Mo(VI), CN-, NO;, SOi- and Cl- were without effect; and 100 pg 1-l magnesium could be tolerated (400 E.cg 1-l in presence of 0.01 M EDTA). Tolerable levels for palladium(I1) were 4 pg 1-l (695 nm) and 25 pg 1-l (310 nm), which were raised to 400 pg 1-i in the presence of 10 mg 1-l cyanide. Of the three methods for obtaining kinetic data, the one presenting the best analytical characteristics, i.e., the smallest amount determinable, greatest precision and fewest interferences, is the initial rate method. This method is therefore recommended. Nature of the reaction. The catalytic reaction probably involves the oxidation of manganese(I1) to Mn(III), and possibly Mn(IV), by atmospheric TABLE 1 Characteristics of the kinetic procedures for manganese(I1) Method
Initial rate Fixed time Fixed absorbance
A = 310 nm
h = 695 nm Useful range (PB I-‘)
R.s.d.’ (%)
Useful range (rg I-‘)
R.s.d.a (%)
0.2-12 l-12b l-10C
2.4 8.0 6.5
0.5-8 1-6b 1-6d
2.1 7.8 4.5
aRelative deviation (n = 11). bTime = 175 s. ‘Absorbance
= 0.38. dAbsorbance
= 0.70.
303 TABLE 2 Determination
of manganese in analytical reagents
Sample
Wavelength (nm)
Reported maximum content (W)
Found (%)
Perchloric acid (Panreac GR) Ammonium iron(I1) sulphate (Merck GR) EDTA (Probus GR)
310
0.00005
0.00002
310
0.05
0.03
695
-
0.00001
oxygen in alkaline medium. The reaction steps are probably: Mn(I1) + l/2 O2 =+Mn(II1) Succinimidedioxime
+ Mn(II1) * oxidation products + Mn(I1)
The spectrum of the oxidation product shows absorption bands at 310 and 695 nm. The blue species is unstable and disappears gradually, whereas the absorbance of the yellow species increases until it becomes constant. The oxidation therefore probably involves the formation of a blue nitroso compound which yields a substance readily oxidized in basic solutions to a yellow nitro compound. This is supported by the fact that when an induction period appears under certain conditions, it is shorter for the blue form. Moreover, oxidation of maleinimidedioxime(I1) first gives a nitroso compound which already possesses aromatic character, so that a yellow product appears instantly, without detection of any blue form. Applications. To test the proposed method, it was applied to the determination of traces of manganese in analytical reagents. In all instances, the standard addition method was employed. In order to detect the existence of possible interferences, the manganese recovery was calculated by comparing the results obtained before and after the addition of the manganese standard solutions. The results obtained for the different aliquots of the prepared solutions (Table 2) indicate the sensitivity of the procedures. REFERENCES 1 2 3 4 5 6 7 8 9 10
F. Buscarons, Mem. R. Acad. Cienc. Artes Barcelona, 41 (1972) 247. C. Mongay and V. Cerda, Quim. Anal., 28 (1974) 271; 29 (1975) 166. M. L. Albelda, V. Cerda, R. Pardo and P. Sanchez-Batanero, Quim. Anal., in press. M. L. Albelda, V. Cerdd and C. Mongay, Bull. Sot. Chii. Fr., (1982) 19. J. Rius, C. Mongay and V. CerdP, Afinidad, 38 (1981) 357. J. Lumbiarres, C. Mongay and V. Cerda, AnaIusis, 8 (1980) 62; J. Thermal Anal., 22 (1981) 275. M. L. Albelda, V. Cerdl and C. Mongay, J. Thermal Anal., 24 (1982) 289. D. Perez-Bendito, M. Vaicarcel, M. Ternero and F. Pino, Anal. Chim. Acta, 94 (1977) 405. E. A. Morgen, N. A. Vlasov and L. A. Kozhemyakina, Zh. Anal. Khim., 27 (1972) 2064. F. Sembritzki, Berichte, 22 (1889) 2958.