Optimization of ion-pair extraction by direct measurement of conditional extraction constants with a membrane phase separator

Cantwell, Frederick F.; Carmichael, Murray

doi:10.1021/ac00241a022

Cited by 13 publications

(14 citation statements)

References 25 publications

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“…Experiments 1 to 5 were done with excess Q+ while experiments 6 to 13 had excess P". In experiments [2][3][4] Cq was held constant and the nonexcess ion P" was varied. Conversely, in experiments 6-10 CP was held constant and the nonexcess ion Q+ was varied.…”

Section: Resultsmentioning

confidence: 99%

“…Chemical Reaction Regime. The ion-pairing chemical reaction could conceivably be occurring in the aqueous phase, at the liquid-liquid interface or in the organic phase, as shown in eq [1][2][3]. Species without a subscript are in the aqueous *i M.T.…”

Section: Theorymentioning

confidence: 99%

“…Since the extraction is quantitative at equilibrium, the rate law will be pseudo first order when one of the reactants Q+ or P" is present in excess. For each of the three cases represented by eq [1][2][3] the integrated extraction rate equation has the form Z A0," \…”

Section: Theorymentioning

confidence: 99%

“…The first-order extraction rate constant (0.41 ± 0.10 s1) calculated from the steady-state portion of the deconvolved A 0 vs f curve Is Independent of the concentration of excess ion Q+ or P™, over the 20-fold concentration range studied. Extraction rate Is controlled by dlffusional mass transfer through the Nernst diffusion layers rather than by the rate of the Ion pairing chemical reaction Itself. While the equilibrium aspects of ion-pair extraction have been extensively studied (1)(2)(3)(4), the kinetic aspects have received much less attention. Under conditions of slow stirring with neither the aqueous nor the organic phase dispersed, the ion-pair extraction of dextromethorphan hydrobromide and of quaternary ammonium bromides had forward first-order rate constants of 10"4 to 10~8 s'1 (5,6).…”

mentioning

confidence: 99%

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Kinetics of ion pair extraction

Cantwell¹,

Freiser²

1988

Anal. Chem.

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Section: Resultsmentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

mentioning

confidence: 99%

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Kinetics of ion pair extraction

Cantwell¹,

Freiser²

1988

Anal. Chem.

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“…The equilibrium aspects of the distribution of ion-pairs between two bulk liquid phases have been extensively studied (1,4) and, more recently, the kinetic aspects of ion-pair extraction between bulk liquid phases have been investigated (5).…”

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confidence: 99%

Adsorption of tetrahexylammonium – bromothymol blue ion-pairs at the chloroform–water interface

Amankwa¹,

Cantwell²

1991

Can. J. Chem.

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LAWRENCE AMANKWA and FREDERICK F. CANTWELL. Can. J. Chem. 69, 88 (1991) Porous membrane phase separators are used to study the adsorption of the cation tetrahexylammonium (Qt), of the anion bromothymol blue (HB-) and of the ion-pair formed between them (QHB) at the liquid-liquid interface in a rapidly stirred mixture of chloroform and aqueous buffer. Adsorption isotherms in all three cases follow the Langmuir equation. The anion HBis much more strongly adsorbed than the ion-pair QHB. The porous membrane technique readily permits measurement of simultaneous adsorption of the two species HB-and QHB, and thereby allows a study of their competitive adsorption. When QHB is adsorbed in the presence of an excess of HB-both the saturated (monolayer) interfacial concentration of QHB and the logarithm of the adsorption equilibrium constant for QHB decrease linearly with an increase in interfacial concentration of HB-. This shows quantitatively that coadsorption of QHB and HB-involves a direct competition for space at the interface and also that the presence of adsorbed HB-changes the adsorbent properties of the interface. Analytical implications for solvent extraction are discussed. Solvent extraction of ion-pairs has been (1) and remains (2,3) an important technique for the analytical determination of ionic species. The equilibrium aspects of the distribution of ion-pairs between two bulk liquid phases have been extensively studied (1,4) and, more recently, the kinetic aspects of ion-pair extraction between bulk liquid phases have been investigated (5).Depending on the surface-activity of the sample ion, of the reagent ion and of the ion-pair formed between them, interfacial adsorption may play a major role in determining both the equilibrium and kinetic extraction behavior of ion-pairs. The use of porous membrane phase separators makes possible measurement of the amount of solute adsorbed at the liquidliquid interface in a vigorously stirred solvent extraction system and therefore permits the measurement of adsorption isotherms of solutes between the interface and the bulk liquid phases (6-9). Adsorption isotherms previously have been measured by this technique for interfacial adsorption of ion-pairs formed between cationic metal-ligand complexes and simple anions (10) and for the ion-pair tetrahexylammoniumpicrate (QP) (1 1). Because the technique allows measurement of concentrations in both liquid phases it makes possible the discrimination of two species simultaneously adsorbed at the interface. This is an advantage over conventional techniques for measuring interfacial adsorption such as those based on interfacial tension or pressure. This advantage is utilized in studying the tetrahexylammonium-bromothymol blue system. 'TO whom correspondence should be addressed.Bromothymol blue is one of the most often used anionic reagents for ion-pair extraction (I). In the present study bromothymol blue anion, HB-, which is surface-active, is used to form a surface-active ion pair, QHB, with tetrahexylammonium cation, Q + , w...

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Polarographic determination of extraction constants

Dingjan

Bennekom

Bult

1987

Pharmaceutisch Weekblad Scientific Edition

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The extraction constant of three organic compounds containing nitrogen as a picrate ion pair in a water-chloroform system were determined by following polarographically the picrate concentration in the aqueous phase as a function of the added amount of reagent. The extraction constants were also determined spectrophotometrically (via batch extraction). The obtained results are in good agreement. The proposed method is applicable for extraction constants with values between 10(3) and 10(9).

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Optimization of ion-pair extraction by direct measurement of conditional extraction constants with a membrane phase separator

Cited by 13 publications

References 25 publications

Kinetics of ion pair extraction

Kinetics of ion pair extraction

Adsorption of tetrahexylammonium – bromothymol blue ion-pairs at the chloroform–water interface

Polarographic determination of extraction constants

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