6533b85cfe1ef96bd12bcae6

RESEARCH PRODUCT

Modeling S-carboxymethyl-L-cysteine protonation and activity coefficients in sodium and tetramethylammonium chloride aqueous solutions by SIT and Pitzer equations

Alba GiacaloneDemetrio MileaClemente BrettiSilvio SammartanoAntonio Gianguzza

subject

Activity coefficientChemistryGeneral Chemical EngineeringPotentiometric titrationInorganic chemistryAnalytical chemistryGeneral Physics and AstronomyProtonationchemistry.chemical_compoundSpecific ion interaction theoryIonic strengthTetramethylammonium chloridePitzer equationsPhysical and Theoretical ChemistrySolubilityCarbocysteine; Solubility; Protonation; Activity coefficients; Dependence on medium and ionic strength

description

Solubility and acid–base properties of S-carboxymethyl-l-cysteine (carbocysteine, ccys) in NaClaq and tetramethylammonium chloride, (CH3)4NClaq ,a tt =2 5 ◦ C and at different ionic strengths were investigated. Solubility was studied at 1.0 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 1.0 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq, while potentiometric measurements (by ISE-H + , glass electrode) were performed at 0.1 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 0.5 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq. Solubility data allowed us to determine Setschenow constants and activity coefficients of neutral carbocysteine (H2ccys). Dependence on ionic strength and ionic medium of protonation constants and activity coefficients was modeled by Specific ion Interaction Theory (SIT) and Pitzer equations. SIT and Pitzer approaches give comparable and satisfactory results. Solubilities and activity coefficients of neutral H2ccys species, protonation constants in NaClaq and (CH3)4NClaq at different ionic strengths, SIT interaction coefficients and Pitzer parameters were calculated, together with protonation constants at infinite dilution: log T K H = p T Ka3 = 9.358 ± 0.001, log T K H 2 = p T K a2 = 3.461 ± 0.001, log

yearjournalcountryeditionlanguage
2007-03-01
10.1016/j.fluid.2006.12.006http://hdl.handle.net/11570/1891739