Binary Diffusion Coefficients of Aqueous Phenylalanine, Tyrosine Isomers, and Aminobutyric Acids at Infinitesimal Concentration and Temperatures from (293.2 to 333.2) K

Abstract

Mutual diffusion coefficients at infinitesimal concentration and atmospheric pressure were measured for binary aqueous solutions of four α-amino acids (2-amino-3-phenylpropanoic acid (phenylalanine), 2-amino-3-(4-hydroxyphenyl)propanoic acid (p-tyrosine), 2-amino-3-(3-hydroxyphenyl)-propanoic acid (m-tyrosine), and 2-amino-3-(2-hydroxyphenyl)propanoic acid (o-tyrosine)) at temperatures from (298.3 to 313.2) K and five aminobutyric acid isomers (2-aminobutanoic acid (α-aminobutyric acid), 2-amino-2-methylpropanoic acid (α-aminoisobutyric acid), 3-aminobutanoic acid (β-aminobutyric acid), 3-amino-2-methylpropanoic acid (β-aminoisobutyric acid), and 4-aminobutanoic acid (γ-aminobutyric acid)) at temperatures from (293.2 to 333.2) K. The diffusion coefficients for each of the amino acids were well-represented by a simple correlation as a function of temperature and solvent viscosity with two adjustable parameters determined for each solute. The two parameters determined for each amino acid in our present and previous studies were closely related to the molar volume of the amino acids at its normal boiling point. We proposed predictive correlations for the diffusion coefficients of aqueous amino acid solutions at infinitesimal concentrations and tested the accuracy of the predictions with the reference data for aqueous amino acids at 298.2 K.

GABA Detection with Nano-ITIES Pipet Electrode: A New Mechanism, Water/DCE–Octanoic Acid Interface

“…The half wave transfer potential, E 1/2 , for GABA detection at the water/DCE–octanoic acid interface is −0.401 ± 0.010 V ( n = 22) versus E 1/2,TBA , which is similar to the value for GABA transfer at the water–HCl/DCE interface. We further calculated the diffusion coefficient for GABA detection at ITIES pipet electrodes using eq as done in our previous work. , Based on multiple independent experimental results with different electrodes, the calculated diffusion coefficient for GABA is 6.09 (±0.58) × 10 –10 m 2 /s ( n = 10), which is consistent with literature values. , The calculated limit of detection (LOD) is 22.4 μM for GABA at nanoITIES pipet electrode of 320 nm in radius. The above experimental results provide the first demonstration of GABA transfer at ITIES interface in an aqueous solution of pH ≈ 7.…”

“…29,30 Based on multiple independent experimental results with different electrodes, the calculated diffusion coefficient for GABA is 6.09 (±0.58) × 10 −10 m 2 /s ( n = 10), which is consistent with literature values. 40,41 The calculated limit of detection (LOD) is 22.4 µM for GABA at nanoITIES pipet electrode of 320 nm in radius. The above experimental results provide the first demonstration of GABA transfer at ITIES interface in an aqueous solution of pH ≈ 7.…”

Molecular dynamics study of structural properties of γ-aminobutyric acid (GABA)

“…Also, many experimental studies about transport properties of GABA have been already performed. Umecky et al and Yui et al measured the binary diffusion coefficient of GABA in infinitesimal aqueous medium at different temperature using Taylor dispersion method [15,16]. Also, viscosity of aqueous solution of GABA was estimated by Romero and Beltron [17].…”

Binary diffusion coefficients of l-histidine methyl ester dihydrochloride in aqueous solutions

“…We have started a comprehensive study of the diffusion of these compounds in aqueous solutions. Diffusion coefficients of some amino acids have previously been reported for aqueous solutions at T = 298.15 K over the concentration range from (0.001 to 0.100) mol Á dm À3 , using measurement by various techniques [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. We concentrate on the important model system of L-histidine methyl ester (as its dihydrochloride, L-HMEDH [31]), for which, as far as the authors know, no data on mutual diffusion coefficients have been published.…”