New ways of enzymatic two-substrate determinations in flow injection systems

This contribution presents two new conceptional strategies for the simultan eous determination of two substrates in flow injection systems. In most bio technological processes, the substrate consumed as well as the product prod uced are of special interest for supervision and control. In most cases, su bstrate and product are interrelated via a redox reaction chain or the law of mass action, respectively. Their enzymatic analysis using dehydrogenases needs often in most cases the use of the cosubstrate in opposite redox sta tes (NAD(+) or NADH). The consequence in a simultaneous two-substrate analy sis is a more complex experimental setup. This paper describes two principa l new concepts, using only one cosubstrate solution and in situ generation of the cosubstrate in the opposite redox state or a procedure using equilib rium constants, respectively. So opposite configuration requirements, or tw o substrates which are interrelated as substrate and product of the enzymat ic analysis can be determined simultaneously, keeping the analysis system m inimised. The determination of ethanol/acetate and the analysis of glucose/ fructose serve as models for the proposed methods. A comparison of the resu lts with established standard analysis kits is given. (C) 2000 Elsevier Sci ence B.V. All rights reserved.