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Partition of Europium(III) with β-diketones and neutral additives between micellar and bulk phases in aqueous nonionic surfactant solutions
Analytica Chimica Acta, 174 (1985) 323-326 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
Short Communication PARTITION OF EUROPIUM( III) WITH P-DIKETONES AND NEUTRAL ADDITIVES BETWEEN MICELLAR AND BULK PHASES IN AQUEOUS NONIONIC SURFACTANT SOLUTIONS
TOMITSUGU TAKETATSU College of General Education,
Kyushu
University,
Ropponmatsu,
Chuo-Ku,
Fukuoka
810
(Japan) (Received 15th January 1985) Summary. The distribution ratio of europium(II1) with a p-diketone and a neutral adduct between micellar and bulk phases in aqueous nonionic surfactant solution was measured by a spectrofluorimetric method as a function of hydrogen ion concentration. The synergic effect of trioctylphosphine oxide for the various p-diketone chelates is much greater than that of tributyl phosphate.
Metal chelates solubilized into a micellar solution of a nonionic surfactant have been applied in various analytical methods such as spectrophotometry [ 1, 21, spectrofluorimetry [3, 41 and titrimetry [5]. Estimation of the distribution ratios of metals with chelate formation between micellar and bulk phases is significant for analytical applications. In the present communication, the distribution ratios are given for europium(II1) with furoyltrifluoroacetone (FTA), pivaloyltrifluoroacetone (PTA), thenoyltrifluoroacetone (TTA), benzoyltrifluoroacetone (BFA) and heptafluorobutanoylpivaloylmethane (HFBPM) in the presence and absence of tributyl phosphate (TBP) and trioctylphosphine oxide (TOPO) adducts in aqueous nona(oxyethylene) dodecyl ether (BL-SEX) solution. The ratios were measured spectrofluorimetrically as a function of hydrogen ion concentration. The variation of the distribution ratio for the Eu/TTA, Eu/TTA/TBP and Eu/TTA/TOPO systems with temperature is also reported. Experimental Stock solution.The concentrations in the mixed stock solution (pH 4.5-5.5) used were 1 X lo5 mol dmm3europium(II1) chloride, 1 X 10s3 mol dm” pdiketone, 1 X 10” mol dmm3acetic acid, 0.2 mol dmm3sodium chloride and 1.0% (w/v) BL-SEX. The concentration of TBP or TOP0 was 1 X 10e3 mol dmm3. Procedure. A portion (10 ml) of the above stock solution was adjusted to approximately the desired pH value with dilute hydrochloric acid, transferred to a 20-ml volumetric flask and made up to volume with water. The solution was poured into a 25-ml stoppered flask and shaken mechanically in a 0003-2670/85/$03.30
0 1985 Elsevier Science Publishers B.V.
324
thermostat wavelength lengths of (HFBPM),
for at least 1 h. The fluorescence was measured at an emission of 610 nm in a l-cm quartz cell with apparent excitation wave370 (FTA), 305 (PTA), 355 (TTA), 345 (BFA) and 320 nm respectively, in the presence and absence of TBP or TOPO.
Results and discussion If the equilibrium equations introduced for the Eu(III)/TTA and Eu(III)/ TTA/TOPO systems [6] can be applied to systems containing the other Pdiketones (HA) and neutral adducts (S), then the EuA3 and EuA& complexes will be formed by the following reactions: Eu& + 3HA,,
= EuA,,,,
+ 3H;,,
(1)
and ELI;& + 3HA,,
+ 2S,,,
= EuA,S,,,,
+ 3H;,,
(2)
Subscripts (b) and (m) refer to the mutually equilibrated bulk and micellar phases, respectively. The equilibrium constants k 1 = [ EuA3] (,,.,)[H+ ] &,/ [Eu~‘]~~,[HA]&) and FzZ = ~~~~~~~1~,~~~‘1~~~/~~~3~1~~~~~~1~~~~~1~~~ me expanded as follows: log k, = IogD,
+ 3 log [H +j c,j - 3 log [HA] c,j
(3)
log kz = log&
+ 3 log [H+] (,,) - 3 log [HA] (,,) - 2 log [S] (mj
(4)
where D1 = [E~A&n,/W~3+l~~~ and D2 = [EuA~S,]&[EU~+]~,,, respectively. When Eqns. 3 and 4 are differentiated with respect to log [H+](,,, then dlog D,/dlog [H+] (,,) = -3 and dlog &/dlog [H+] (,,) = -3 are obtained; here, the concentrations of HA and S can be assumed to be constant because they are in large excess relative to europium(II1). If it can be assumed that the concentration of europium(II1) in the micellar phase is linearly proportional to the fluorescence intensity, and that almost all the europium(II1) species exist in the micellar phase, then in the pH range for which the intensity is constant and maximal, the values of D1 and DZ can be calculated by using the fluorimetric data. The equilibrium constant Pad for the adduct formation in the micellar phase Ed3,,,
+
=,,,
=
E=43S,,,,
is aerived from the values of k 1 and kz : Pad
=
FW%l
~m,/D&I ,m,[Sl $nm, = k&l
(5)
Figure 1 shows that all the plots of log D1 vs. log [H’] (,,) and log D2 vs. log [H’] (,,) are almost linear (about -3). The values of log kl, log kz and log pad can be estimated by using the equations described above. These values are given in Table 1. The apparent equilibrium constants for the EuA3 chelate formation increase in the order FTA < PTA < TTA < BFA < HFBPM and the synergic effect of TOP0 on the EuA3S2 adduct formation in the micellar phase is much greater than that of TBP.
325
I
I
10-5
I
10-4
[~+](t,,,mol
I
10-3
I
10-Z
b.
1
lo-
’
dmm3
10-4
&
10-3
10-z
moldmm3 [H+](L,,,
Fig. 1. Variation of the distribution ratio in the different systems as a function of hydrogen ion concentration. (a) Eu/HA; (b) Eu/HA/TBP; (c) Eu/HA/TOPO. (0) FTA; (0) PTA, (0) TTA; (0) BFA; (e) HFBPM. Fig. 2. Variation of distribution ratio in Eu/TTA, systems as a function of hydrogen ion concentration Fig. 1; (0) lO”C, (b) 15°C; (0) 20°C; (e) 25°C.
Eu/TTA/TBP and Eu/TTA/TOPO at various temperatures: (a-c) as m
Figure 2 shows that the graphs of log II1 vs. log [H’lo,, and log D, vs. log [H+] (,,) for the Eu/TTA, Eu/TTA/TBP and Eu/TTA/TOPO systems are almost linear (about -3), irrespective of temperature used. The Eu/TTA chelating reaction is endothermic and enthalpy change AH was estimated to be about 75 kJ mol-’ by van’t Hoff equation. The enthalpy changes on the adduct formation m the micellar phase were ca. 30 and -34 kJ mol-’ for the Eu/TTA/TBP and Eu/TTA/TOPO systems, respectively.
326 TABLE 1 Apparent equilibrium at 298 K p-Diketone
FTA PTA TTA BFA HFBPM
constants for Eu/HA,
Eu/‘I”l?A/TBP and Eu/TTA/TOPO
EuA,
EuA, (TBP),
log k,
log k,
log
-5.1 -4.0 -3.4 -2.4 -6.3
3.9 5.1 5.7 7.4 9.2
9.0 9.1 9.1 9.8 9.5
EuA, (TOPO), Pad
log k,
hit Pad
8.5 9.0 10.1 11.2 13.5
13.6 13.0 13.5 13.6 13.8
REFERENCES 1 2 3 4 5 6
T. T. T. T. S. T.
Taketatsu Taketatsu, Taketatsu Taketatsu, Okawa, B. Taketatsu,
and A. Sato, Bull. Chem. Sot. Jpn., M. Aihara and Y. Kimoto, Bunseki and A. Sato, Anal. Chim. Acta, 108 Talanta, 29 (1982) 397. Kominami and A. Kawase, Bunseki Chem. Lett., (1981) 1057.
53 (1980) 3713. Kagaku, 30 (1981) 328. (1979) 429. Kagaku, 29 (1980)267.
systems
Short Communication PARTITION OF EUROPIUM( III) WITH P-DIKETONES AND NEUTRAL ADDITIVES BETWEEN MICELLAR AND BULK PHASES IN AQUEOUS NONIONIC SURFACTANT SOLUTIONS
TOMITSUGU TAKETATSU College of General Education,
Kyushu
University,
Ropponmatsu,
Chuo-Ku,
Fukuoka
810
(Japan) (Received 15th January 1985) Summary. The distribution ratio of europium(II1) with a p-diketone and a neutral adduct between micellar and bulk phases in aqueous nonionic surfactant solution was measured by a spectrofluorimetric method as a function of hydrogen ion concentration. The synergic effect of trioctylphosphine oxide for the various p-diketone chelates is much greater than that of tributyl phosphate.
Metal chelates solubilized into a micellar solution of a nonionic surfactant have been applied in various analytical methods such as spectrophotometry [ 1, 21, spectrofluorimetry [3, 41 and titrimetry [5]. Estimation of the distribution ratios of metals with chelate formation between micellar and bulk phases is significant for analytical applications. In the present communication, the distribution ratios are given for europium(II1) with furoyltrifluoroacetone (FTA), pivaloyltrifluoroacetone (PTA), thenoyltrifluoroacetone (TTA), benzoyltrifluoroacetone (BFA) and heptafluorobutanoylpivaloylmethane (HFBPM) in the presence and absence of tributyl phosphate (TBP) and trioctylphosphine oxide (TOPO) adducts in aqueous nona(oxyethylene) dodecyl ether (BL-SEX) solution. The ratios were measured spectrofluorimetrically as a function of hydrogen ion concentration. The variation of the distribution ratio for the Eu/TTA, Eu/TTA/TBP and Eu/TTA/TOPO systems with temperature is also reported. Experimental Stock solution.The concentrations in the mixed stock solution (pH 4.5-5.5) used were 1 X lo5 mol dmm3europium(II1) chloride, 1 X 10s3 mol dm” pdiketone, 1 X 10” mol dmm3acetic acid, 0.2 mol dmm3sodium chloride and 1.0% (w/v) BL-SEX. The concentration of TBP or TOP0 was 1 X 10e3 mol dmm3. Procedure. A portion (10 ml) of the above stock solution was adjusted to approximately the desired pH value with dilute hydrochloric acid, transferred to a 20-ml volumetric flask and made up to volume with water. The solution was poured into a 25-ml stoppered flask and shaken mechanically in a 0003-2670/85/$03.30
0 1985 Elsevier Science Publishers B.V.
324
thermostat wavelength lengths of (HFBPM),
for at least 1 h. The fluorescence was measured at an emission of 610 nm in a l-cm quartz cell with apparent excitation wave370 (FTA), 305 (PTA), 355 (TTA), 345 (BFA) and 320 nm respectively, in the presence and absence of TBP or TOPO.
Results and discussion If the equilibrium equations introduced for the Eu(III)/TTA and Eu(III)/ TTA/TOPO systems [6] can be applied to systems containing the other Pdiketones (HA) and neutral adducts (S), then the EuA3 and EuA& complexes will be formed by the following reactions: Eu& + 3HA,,
= EuA,,,,
+ 3H;,,
(1)
and ELI;& + 3HA,,
+ 2S,,,
= EuA,S,,,,
+ 3H;,,
(2)
Subscripts (b) and (m) refer to the mutually equilibrated bulk and micellar phases, respectively. The equilibrium constants k 1 = [ EuA3] (,,.,)[H+ ] &,/ [Eu~‘]~~,[HA]&) and FzZ = ~~~~~~~1~,~~~‘1~~~/~~~3~1~~~~~~1~~~~~1~~~ me expanded as follows: log k, = IogD,
+ 3 log [H +j c,j - 3 log [HA] c,j
(3)
log kz = log&
+ 3 log [H+] (,,) - 3 log [HA] (,,) - 2 log [S] (mj
(4)
where D1 = [E~A&n,/W~3+l~~~ and D2 = [EuA~S,]&[EU~+]~,,, respectively. When Eqns. 3 and 4 are differentiated with respect to log [H+](,,, then dlog D,/dlog [H+] (,,) = -3 and dlog &/dlog [H+] (,,) = -3 are obtained; here, the concentrations of HA and S can be assumed to be constant because they are in large excess relative to europium(II1). If it can be assumed that the concentration of europium(II1) in the micellar phase is linearly proportional to the fluorescence intensity, and that almost all the europium(II1) species exist in the micellar phase, then in the pH range for which the intensity is constant and maximal, the values of D1 and DZ can be calculated by using the fluorimetric data. The equilibrium constant Pad for the adduct formation in the micellar phase Ed3,,,
+
=,,,
=
E=43S,,,,
is aerived from the values of k 1 and kz : Pad
=
FW%l
~m,/D&I ,m,[Sl $nm, = k&l
(5)
Figure 1 shows that all the plots of log D1 vs. log [H’] (,,) and log D2 vs. log [H’] (,,) are almost linear (about -3). The values of log kl, log kz and log pad can be estimated by using the equations described above. These values are given in Table 1. The apparent equilibrium constants for the EuA3 chelate formation increase in the order FTA < PTA < TTA < BFA < HFBPM and the synergic effect of TOP0 on the EuA3S2 adduct formation in the micellar phase is much greater than that of TBP.
325
I
I
10-5
I
10-4
[~+](t,,,mol
I
10-3
I
10-Z
b.
1
lo-
’
dmm3
10-4
&
10-3
10-z
moldmm3 [H+](L,,,
Fig. 1. Variation of the distribution ratio in the different systems as a function of hydrogen ion concentration. (a) Eu/HA; (b) Eu/HA/TBP; (c) Eu/HA/TOPO. (0) FTA; (0) PTA, (0) TTA; (0) BFA; (e) HFBPM. Fig. 2. Variation of distribution ratio in Eu/TTA, systems as a function of hydrogen ion concentration Fig. 1; (0) lO”C, (b) 15°C; (0) 20°C; (e) 25°C.
Eu/TTA/TBP and Eu/TTA/TOPO at various temperatures: (a-c) as m
Figure 2 shows that the graphs of log II1 vs. log [H’lo,, and log D, vs. log [H+] (,,) for the Eu/TTA, Eu/TTA/TBP and Eu/TTA/TOPO systems are almost linear (about -3), irrespective of temperature used. The Eu/TTA chelating reaction is endothermic and enthalpy change AH was estimated to be about 75 kJ mol-’ by van’t Hoff equation. The enthalpy changes on the adduct formation m the micellar phase were ca. 30 and -34 kJ mol-’ for the Eu/TTA/TBP and Eu/TTA/TOPO systems, respectively.
326 TABLE 1 Apparent equilibrium at 298 K p-Diketone
FTA PTA TTA BFA HFBPM
constants for Eu/HA,
Eu/‘I”l?A/TBP and Eu/TTA/TOPO
EuA,
EuA, (TBP),
log k,
log k,
log
-5.1 -4.0 -3.4 -2.4 -6.3
3.9 5.1 5.7 7.4 9.2
9.0 9.1 9.1 9.8 9.5
EuA, (TOPO), Pad
log k,
hit Pad
8.5 9.0 10.1 11.2 13.5
13.6 13.0 13.5 13.6 13.8
REFERENCES 1 2 3 4 5 6
T. T. T. T. S. T.
Taketatsu Taketatsu, Taketatsu Taketatsu, Okawa, B. Taketatsu,
and A. Sato, Bull. Chem. Sot. Jpn., M. Aihara and Y. Kimoto, Bunseki and A. Sato, Anal. Chim. Acta, 108 Talanta, 29 (1982) 397. Kominami and A. Kawase, Bunseki Chem. Lett., (1981) 1057.
53 (1980) 3713. Kagaku, 30 (1981) 328. (1979) 429. Kagaku, 29 (1980)267.
systems