Flow Injection Determination of Urinary Protein Using Fluorescence Quenching of Tetraiodofluorescein

A flow injection analysis system with spectrofluorimetric detection has been developed for trace protein in urine. The protein assay is based on the ion-association of protein and tetraiodofluorescein (TIF) in the presence of Triton X-100 at pH 3.2. Although the TIF-protein ion associate produces red color compounds, fluorescence quenching caused by bonding with protein was measured at 560 nm (excitation: 313 nm). The quenching is applied to the protein determination. Linearity range was up to 10 mg/L bovine serum albumin and the correlation coefficient was 0.999. The detection limit (S/N = 3) was 0.6 mg/L with RSD 0.134% (n = 4). The FI system is available for rapid screening in diabetic diagnosis.