Erythrocyte porphyrin analysis in the detection of lead poisoning in children: evaluation of four micromethods.

We evaluated four procedures for determination of erythrocyte porphyrin: double extraction with ethyl acetate/acetic acid-HCl, single extraction with ethanol, single extraction with acetone, and direct solubilization with detergent-buffer. The ethyl acetate procedure, when used with two portions of HCl, apparently gives complete recovery of porphyrin and is suitable for reference as a comparison method. The ethanol procedure gives a high and consistent recovery and is technically simpler. The acetone procedure gives low and variable recovery of porphyrin, and the detergent-buffer method is subject to serious hemoglobin interference; neither of these two procedures offers any technical advantage. Stability of samples and methods for standardization were explored. A procedure for expressing results in terms of erythrocyte Zn-protoporphyrin content is given. Because of its stability, coproporphyrin is useful as a daily working standard. The ethyl acetate and ethanol methods are about equally efficient for detecting lead intoxication. Because of its simplicity, the ethanol method seems to be the best for use in screening.