Fabrication of an optical chemical sensor based on immobilised tris (1,10-phenantroline)-iron(III) complex (ferriin) onto modified polyvinyl alcohol (PVA) membrane for the determination of uric acid (UA) is described. The immobilised ferriin will be reduced to tris (1,10-phenantroline)-iron(II) complex (ferroin) in the presence of UA, which in turn causes change in colour from colourless to the red. The colour change could be related to the concentration of UA in the samples. The PVA as a solid support matrix has been modified using hydrogen sulphate in order make the membrane harder, elastics and resistant toward water. Therefore the membrane can be easily handled as a strip and work properly in aqueous samples particularly clinical samples (e.g. urine and serum). The ferriin membrane has been employed as a disposable strip that can be placed inside cuvette test for a simple spectrophotometric measurement at wavelength 510 nm. For clinical applications, calibration curves were obtained for UA over the concentration range at 0-0.6 mg/ml in slightly acid condition (pH 6) with a detection limit (3σ) of 1.55 mg/ml. The interference from reductant molecules, which often are present in clinical samples (e.g. ascorbic acid, urea etc), are investigated. The practical utility of the present ferriin membrane is demonstrated by measuring UA in human urine samples. The results obtained by the ferriin membrane are compared with those obtained by a standard method.
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