Interaction of l-Phenylalanine with Nicotinic Acid in Buffer Solution by Volumetric Measurements at Various Temperatures

Abstract

The interaction between l-phenylalanine (Phe) and nicotinic acid (NA) was studied in aqueous phosphate buffer solutions (pH 7.35) by a volumetric method. Densities of l-phenylalanine–buffer, NA–buffer and l-phenylalanine–NA–buffer mixtures were determined at T = (288.15, 298.15, 303.15, 308.15 and 313.15) K using a DSA 5000 M (Anton Paar) density meter. The apparent molar volumes of NA (\( {}^{\phi }V_{\text{NA}} \)) in buffer solution and in buffer–amino acid solutions were evaluated. The concentration of NA was varied from (0.0023 to 0.0364) mol·kg−1. The interaction of Phe with NA is accompanied by complex formation. The partial molar volumes of transfer of NA from buffer to buffer–amino acid solutions are positive. The results are discussed in terms of various interactions operating in this system.