Simultaneous enzymatic/electrochemical determination of glucose and L -glutamine in hybridoma media by flow-injection analysis.

Abstract

A split-stream flow-injection analysis system is described for simultaneous determination of glucose and L -glutamine in serum-free hybridoma bioprocesses media. Amperometric measurement of glucose is based on anodic oxidation of hydrogen peroxide produced by immobilized glucose oxidase within a triple layer membrane of an integrated flow-through glucose-selective biosensor. Determination of L -glutamine is based on quantitating ammonium ions produced in a flow-through enzymes reactor containing immobilized glutaminase enzyme, and subsequent downstream potentiometric detection of these ions by a nonacting-based ion-selective polymer membrane electrode. Endogenous potassium and ammonium ion interference in the L -glutamine determination are eliminated by using a novel in-line tubular cation-exchange membrane unit to exchange these interferent species for cations undetectable by the membrane electrode. The first generation split-steam flow-injections system can assay 12 samples/h using direct injections of 50 ΜL of media samples, with linear responses to glucose in the range of 0.03 to 30m M , and log-linear response to L -glutamine from 0.1 to 10 m M . © 1993 Wiley & Sons, Inc.