Long-path photometry in clinical analysis: I. The determination of chromium using diphenylcarbazide

Abstract

The diphenylcarbazide method for determining chromium in biological material was reinvestigated and scaled down to require only 0.2 ml (or 0.2 g) of sample. The samples are digested at 300 °C within 1 hr by a mixture of concentrated sulfuric, nitric, and perchloric acids in a volume ratio 75:15:10. Chromium is oxidized to dichromate with permanganate and the excess of the latter is destroyed by azide. The color reagent is added and the absorbance is measured in a 20-cm long-path microcell requiring less than 0.3 ml of solution. Results on serum pools shown a standard deviation of about ±1.1 ng of Cr/ml of serum for contents in the range of 25 ng/ml. The results compare very favorable with those obtained by flameless atomic absorption. The determinations can be made by using a simple, dedicated photometer consisting of the long-path cell with a green LED attached to one window and a phototransistor to the other and needing only very simple circuits and low battery power.