[Determination of total urinary porphyrins by derivative spectroscopy (author's transl)].

The principle of derivative spectroscopy is the basis of a new procedure for determining total urinary porphyrins. The 2nd derivative of the normal spectrum isolates the Score band of the porphyrins from the background absorption and enables the quantitative evaluation without correction factors. The new procedure is more sensitive than the classical method using measurement at three wavelengths and permits reliable determinations in the normal range. The short analysis time and the low reagent requirement allow economic screening. Normal and slightly increased contents of total urinary porphyrins can be reliably determined in undiluted urine samples up to 0.16 mumol/1. A dilution is required for higher concentrations. The sensitivity for 0.01 mumol/1 total porphyrins in urine is 0.06 absorbance units. The coefficient of variation for the series determination of samples with 0.07 mumol/1 is about 1%.