Partition Coefficients and Solubilities of α-Amino Acids in Aqueous 1-Butanol Solutions

Abstract

The partition coefficients of seven α-amino acids in the system water + 1-butanol have been measured at 25 °C from the very dilute region up to saturation. The solubilities of these amino acids in the pure solvents and in the miscible composition range of the solvent system have also been studied in this work. It was found that the partition coefficients of the amino acids and the composition of the phase-partitioning system are strongly dependent on the amino acid concentration and on the chemical nature of their side-chain moiety. The experimental data were successfully correlated with a thermodynamic model which describes conveniently defined excess solubilities via a simple excess Gibbs energy model having a single amino acid specific parameter. In addition, a simple method for the estimation of the solubility of amino acids in pure alkanols is presented.

Solubility of Amino Acids, Sugars, and Proteins

“…For mixed solvent systems, the works by Orella and Kirwan [21] and Gude et al [22,30] are worth a mention. Orella and Kirwan used an excess solubility approach with the Wilson equation.…”

“…In fact, the majority of the data available is at 25 °C: water-ethanol [16][17][18], water-methanol [19], and more recently, water-propan-1-ol, water-propan-2-ol [20,21], and water-butan-1-ol [22] systems. With the aim to extend the database already available, new measurements were carried out, by Macedo and coworkers, for glycine and DL-alanine in the aqueous systems of ethanol, propan-1-ol, and propan-2-ol, in the temperature range between 25 and 60 °C, using the analytical gravimetric method [23].…”

“…Gude et al [22,30] presented a simpler model, also based on the excess solubility approach, which is a combination of a combinatorial term based on the Flory-Huggins (FH) theory with a Margules residual expression. This methodology is very attractive because simultaneous representation of solid-liquid and liquid-liquid equilibria with only one ternary Margules interaction parameter is achieved.…”

Solid-liquid equilibrium data of amoxicillin and hydroxyphenylglycine in aqueous media

“…Diender et al (1998) determined the solubility of HPG, 6-APA and AMOX in water as function of pH at 298.15 K according to the analytical method proposed by Gude et al (1996). Using this method, Vieira (2003) determined the solubility of phenylglycine methyl ester (EMPG), ampicillin (AMPI), 6-APA and phenylglycine (PG) in water at 298.15 K as a function of pH.…”

“…The optimal conditions according to these data were found to be in the range of pH between 6 and 7, the precipitation of ampicillin being effective only at pH below 7.5. Santana et al (2010) determined the solubility for a series of the components involved in the enzymatic synthesis of ampicillin at different values of temperature and pH, using the saturation method proposed by Gude et al (1996) and modified by Vieira (2003). In order to describe the measured solubilities, the model of Khoshkbarchi and Vera (1996) was applied.…”