Kinetic Approach to Determine 3-Amino Methyl Hexanoic Acid in Pharmaceutical Formulations

A simple and sensitive colorimetric spectrophotometric method based on application of chemical kinetics was produced and developed for the quantitative determination of 3-amino methyl hexanoic acid (pregabalin) in bulk and pharmaceutical preparations. Ninhydrin, a chromogenic agent was reacted with pregabalin at 70 °C and the absorbance was measured at 575 nm and kinetic correlation was evaluated between absorbance and time. The initial-rate, rate-constant and fixed-time (80 min) methods were employed for the estimation of pregabalin in the range of 10–30 μg mL which showed good correlation >0.9990 in all three cases with LOQ values ranging from 1.2–1.5 μg mLand LOD values ranging from 0.76–0.95 μg mL. Method validation was carried out using ICH recommendations and the variables were evaluated and optimized. The newly developed method has useful applications to determine pregabalin in pharmaceutical formulation with good recovery (98.38 to 102.12 %t) and precision (RSD < 1.4 %). Standard free energy changes and association constant were found to be 1.212 × 10 and –4.747, respectively, as determined by the Benesi–Hildebrand equation.