On-line 'protein shaker': A multicommutated flow analysis system for fluorometric creatinine determination in...

A fully mechanized multicommutated flow analysis (MCFA) system for fluorometric determination of creatinine in serum samples is introduced in this paper. The flow system was constructed with microsolenoid pumps and valves and with a 3D-printed flow cell. Fluorometric assay relied on creatinine reaction with 3,5-dinitrobenzoic acid and hydrogen peroxide in an alkaline environment. To overcome significant interference from protein, a flow reactor for serum deproteinization was designed and implemented in the flow system. The deproteinization was carried out by precipitation with trichloroacetic acid and the addition of sodium chloride facilitated the precipitate sedimentation. The supernatant representative sample was pumped out and subjected to fluorometric creatinine assay. The obtained linear range was from 1.6 to 500 μmol L^-1 and the precision, expressed as RSD, was below 3%. The proposed MCFA system was used to determine creatinine concentration in control serum samples. The results obtained with flow deproteinization correlated well with results obtained with conventional deproteinization (y = (0.91 ± 0.09) x + (37 ± 28)) with Pearson's r 0.979.