Series approach to modeling of amino acid and electrolyte mixtures in the aqueous media

• Modeling for the electrolyte, amino acid/peptide and water solutions using activity coefficient (AC) approach at 298.15 K.
• The equations are tested against the large number of experimental data sets.
• The comparison shows that the PE model can correlate the AC data of ternary systems more accurately than the other PSC.

In this work, the electrolyte, amino acid and water solutions are modeled using activity coefficient (AC) approach. Two different models, modified Pitzer ion interaction equation proposed by Esteso (PE) and the Pitzer–Simonson–Clegg model (PSC) are used in their original and modified forms to correlate the activity coefficient and osmotic coefficient data for binary and ternary systems containing water, amino acid/peptide and electrolytes. The considered aqueous systems contain one of the eight amino acids: alanine, glycine, serine, threonine, β-alanine, methionine, α-amino n-butyric acid and α-amino butyric acid. Also, glycylglycine is used as one peptide. The salts are NaCl, NaBr, NaNO3, KCl and KBr.The results obtained from the studied models are compared to those of experimental data. The comparison shows that the PE model can correlate the experimental AC data of ternary systems more accurate than the other PSC. The equations are tested against the large number (30) of available experimental data sets.