AbstractA novel split‐stream flow‐injection system is described for the determination of creatinine in urine samples. The system is based on the use of a microreactor with immobilized creatinine iminohydrolase and downstream potentiometric detection of ammonium ions using a nonactin‐based membrane electrode. Splitting of the sample into two branches of the flow system, with the concomitant addition of alkali metal ions to the carrier solution, allows for simple correction of endogeneous ammonia and alkali metal ion levels via operation of the electrode in the sub‐Nernstian linear response range. The analytical utility of the system developed is illustrated by accurate creatinine determinations in urine
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