An alternative, single-point method for creatinine determination in urine samples with optoelectronic detector. Critical comparison to Jaffé method.

A rapid, single-point method for colorimetric creatinine determination has been developed as an alternative for a well-established Jaffé assay, which lacks analytical specificity. 3,5-dinitrobenzoic acid was employed in an alkaline environment as a chromophore instead of picric acid. Apart from the spectrophotometer, a simple optoelectronic detector was applied as an alternative detection method. The conditions of the reaction were optimized to provide satisfactory analytical parameters. The linear ranges of the proposed assays were 40-4000 and 10-300 µmol L of creatinine for conventional spectrophotometry and a PEDD detector, respectively. A broad spectrum of potential interferents was examined. The presence of compounds such as glucose, urea or uric acid was the source of a significantly smaller bias in the examined method than in the case of the Jaffé method variants. The presented method was validated with the use of 10 human urine samples with the creatinine level determined by the recommended method. Two-tail paired Student's t-tests with 9 degrees of freedom at the 95% confidence level showed the agreement between the proposed and the reference methods.