Amperometric analysis with a copper electrode for determination of amino acids

Abstract

This thesis presents a study on the amperometric behavior of a copper electrode towards amino acids in batch and flow system. In batch system, the effect of buffer solution, stirred speed and amino acids concentration were studied. It was found that phosphate buffer pH 7.0 was the most suitable buffer. The increase of the current caused by amino acids was linearly in the range of 10-5 – 10-4 M and detection limit was in the range of 10-7 – 10-8 M. In flow system, the influences of flow rate, residence time, amino acid concentration and sample injection volume were examined. Injection of 10-4 – 10-1 M glycine and threonine, and 10-5 – 10-3 M cysteine in volume of 10 L gave sharp response peaks in the linear range; the relative standard deviation for peak-height measurements was 1.0-1.5% and the detection limits of 10-5 M were obtained. Finally, the application of a copper electrode as and amperometric detector for amino acids in reverse-phase high performance liquid chromatography was demonstrated. For the separation of five amino acids, viz. threonine, methionine, arginine, phenylalanine and tryptophan, detection limits in the range of 10-5 M were determined with retention times varying from 3-11 min.