Rapid, sensitive micro blood lead analysis: a mass screening technique for lead poisoning.

A rapid micro blood lead method is described. Analyses were performed on 20-microL blood samples spotted on filter paper, collected in graduated heparinized capillary glass tubes following finger pricks. The samples were air dried on filter paper and mailed to the laboratory in glassine envelopes. These samples stored on filter paper are stable for at least six months. The blood spots were punched out with a 1/4-in. diameter hole punch and placed in Delves cups for insertion into the flame atomic absorption spectrometer. The innovation of this method is that an ashing step precedes sample introduction into the flame. In phase 1, the Delves cup with the blood sample is pushed 1 cm from the flame. The heat is sufficient for the filter paper to ignite and burn to completion in seconds. After the smoke dissipates, the samples are introduced into the flame for lead analysis, reading the signal at 283.3 nm. The entire analysis time is 15 s per sample. The limit of quantitation is 4 micrograms/dL of lead. Standard curves were linear from 4-42 micrograms/dL. The average CV for this range is 8.2%. The comparative study between the MIBK extraction method and this method yielded a correlation coefficient r = .99 (n = 55). The method is fast, practical, economical, and easily adaptable to screen large numbers of micro lead samples.