LIQUID CHROMATOGRAPHIC DETERMINATION OF LYSINE BY POTENTIOMETRIC DETECTION WITH A BIOSENSOR

A liquid chromatographic method with potentiometric detection using a lysine biosensor is proposed for the determination of lysine in pharmaceutical samples. The method is based on the separation of lysine from other species by micellar liquid chromatography and on-line neutralization of the eluent with a lithium hydroxide solution. This neutralization process is required to render the pH of the chromatographic effluent compatible with the enzymatic detection of lysine. The biosensor is composed of a lysine oxidase membrane attached to an ammonium electrode, in such a way that the ammonium generated in the enzymatic degradation of the substrate is monitored potentiometrically. The effect of experimental variables such as the acidity and composition of the mobile phase and the pH on the biosensor response is studied to optimize the detection conditions. Results obtained in the analysis of lysine in pharmaceutical preparations are compared with those obtained by the standard method. A good concorda...