Studies in lipid histochemistry. XIII. The OPA (osmiumtetroxide-periodic acid-alpha-naphthylamine) method for the detection of apolar lipids.

A new procedure for the detection of apolar lipids is described. It is a modification of the OTAN method (Adams, 1959) using periodic acid which oxidatively removes lower osmium derivatives from polar sites only, leaving those in apolar lipids intact and demonstrable with alpha-naphthylamine. Control steps for the exclusion of the possible interference of some less polar complex lipids and of lipopigments are described. The described technic is superior to the conventionally used sudan dyes due partly to the fact that only aqueous solutions are employed thus excluding any extraction of lipids, partly to the more distinct coloration.