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

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.