Multicommutation in flow analysis. Part 3. Spectrophotometric kinetic determination of creatinine in urine exploiting a novel zone sampling approach

Zone sampling performed on a single analytical channel and associated with the stopped-flow approach was proposed and applied to the spectrophotometric kinetic determination of creatinine in urine based on Jafféʹs reaction. The flow network comprised microcomputer controlled three-way solenoid valves. With multicommutation, the potentialities of zone sampling and stopped-flow were expanded, and the design of the flow set up was simplified. Influence of the main related parameters such as system configuration, reagent concentrations, temperature and timing were studied. The proposed system handled about 24 samples per hour. Baseline drift was not observed during extended operation periods (8 h). Sample pretreatment was not required. Results were reproducible (R.S.D. < 3%) and in agreement with those obtained in a batch procedure.