New possibilities for open–closed flow-injection systems: an approach to interference removal

Abstract

A new use of the open–closed approach for quantification of the disturbing effect of interferents is reported. The principle of the method is based on monitoring the signal from the interferent before development of the derivatization reaction. After the first passage of the sample plug through the detector, the flow system is closed, and the derivatization reaction is developed and monitored as many times as the reactant plug is recirculated. The approach has been applied to the enzymatic–fluorimetric determination of potassium in serum, where the interference from ammonium is also enzymatically removed before passage of the sample plug through the pyruvate kinase and lactate dehydrogenase reactor for the determination of the analyte.