Filter paper-disc method for the determination of zinc protoporphyrin in blood.

Zinc protoporphyrin, an abnormal metabolite resulting from undue lead absorption, can be quantitatively determined in blood that has been spotted and dried on filter paper. This procedure, which yields values that correlate well (r = 0.96) with those obtained by direct determination in whole blood, offers advantages in convenience of collection, storage, and transportation that recommend it for field use. The light sensitivity of the zinc protoporphyrin, however, mandates that the specimens be protected from excessive light exposure until analyzed.