A multi-purpose flow system based on multi-commutation

A multi-purpose flow system designed with solenoid valves and micropumps is proposed. The independent control of each active device was exploited to implement dilutions, calibration with a single solution, standard additions, titrations and strategies to increase sample residence time without changing the manifold hardware. Sample dispersion coefficients between 1 and 7800 were achieved by changing the sample volume and exploiting zone sampling, with coefficient of variation estimated as 6.5% for the highest dilution. Calibration curves obtained from a single standard showed slopes in agreement with those obtained by conventional batch dilutions with variations of lower than 2% between days. The possibility of implementing the standard addition method or the stopped-flow approach at different points of the manifold was demonstrated for creatinine determination in urine by the Jaffe reaction. Analytical curves for different sample residence times can be obtained for detecting matrix effects or for the analysis of colored samples. Titrations by the continuous variation method or binary search, as well as other possible applications, are discussed.