A Quantitative Assay for Urinary Porphobilinogen.

A procedure has been developed for the rapid, quantitative determination of urinary porphobilinogen. Interfering substances are removed by selectively adsorbing the porphobilinogen with an ion-exchange resin using a batch method. After acid elution of the porphobilinogen, Ehrlich’s reagent is added to produce the chromophore, which is then measured spectrophotometrically. Obtaining absorption at two wavelengths permits a differentiation of porphobilinogen from interfering reactants not removed by the resin treatment. This assay is relatively simple, dependable, highly reproducible for increased amounts, and more specific than the qualitative assay.