A multicommuted flow system for the determination of dextrose in parenteral and hemodialysis concentrate solutions.

A new method is presented for the automation of the determination of dextrose in parenteral and hemodialysis solutions. The method is based on multicommutation flow analysis (MCFA) and exploits enzymatic reactions providing a colored derivative that is detected spectrophotometrically (Trinder's method). The reagent, comprising glucose oxidase, peroxidase, 4-hydroxybenzoate and a buffer was obtained from a commercial kit for the determination of glycemia. The flow system used three 3-way solenoid valves operating under computer control. The necessary software was developed for the purpose and compiled in QuickBASIC 4.0 The influence of some operating variables (segment size, number of segments and reactor length) was studied. Calibration curves in the range 0-1g/L presented a slight curvature and were fitted with a second-degree polynomial (h=-0.0632C(2)+0.6039C+0.166, r(2)=0.9973, h being the peak-height (absorbance) and C the concentration in g/L). The method was validated by analyzing artificial samples presenting accurately known concentrations of dextrose, and comparing the results with the known value and with value obtained by polarimetry. Recoveries were in the range 96.6-100.2%, and the difference with the polarimetric analysis was in the range 0.1-3.3%. Precision (R.S.D.,%) was better than 2.4%. Sampling frequency of the system was 90 samples/h, with a reagent consumption of 0.14 mL per sample.