On-line ‘protein shaker’: A multicommutated flow analysis system for fluorometric creatinine determination in deproteinized serum

A fully mechanized multicommutatedflow analysis (MCFA) system forfluorometric determination ofcreatinine in serum samples is introduced in this paper. Theflow system was constructed with micro-solenoid pumps and valves and with a 3D-printedflow cell. Fluorometric assay relied on creatininereaction with 3,5-dinitrobenzoic acid and hydrogen peroxide in an alkaline environment. To overcomesignificant interference from protein, aflow reactor for serum deproteinization was designed andimplemented in theflow system. The deproteinization was carried out by precipitation with trichloro-acetic acid and the addition of sodium chloride facilitated the precipitate sedimentation. The supernatantrepresentative sample was pumped out and subjected tofluorometric creatinine assay. The obtainedlinear range was from 1.6 to 500mmol L1and the precision, expressed as RSD, was below 3%. Theproposed MCFA system was used to determine creatinine concentration in control serum samples. Theresults obtained withflow deproteinization correlated well with results obtained with conventionaldeproteinization (y¼(0.91±0.09) xþ(37±28)) with Pearson's r 0.979.