An improved capillary blood-filter paper-graphite furnace atomic absorption spectrometric method for lead screening

A revised procedure for processing a capillary blood sample collected on filter paper (FP) for analysis by graphite furnace atomic absorption spectrometry (GFAAS) is described. A 1/4-in. diameter disk of the dried FP sample was used, and a correlation of 0.975 with a false-positive rate of 0.8% and a false-negative rate of 1.7% was found when the results from the FP sample and its corresponding venous sample were compared. Several analytical variables were investigated, and the following was found: blood samples with hematocrit values of 30-39% did not show any significant differences between the paired FP and venous lead results; filter paper blank values were < 2 micrograms/dl with the use of aqueous standards without correction and 0.1 microgram/dl with paper blank correction; and during the collection of 163 samples from 6 different urban sites over a period of 1 year, no environmental lead contamination was encountered based upon the good agreement between all of the paired FP and venous lead results. The method described is easier to perform than an earlier version. All indications suggest that a fingerstick capillary blood sample collected on filter paper is suitable for lead screening. Proper precautions must always be taken to guard against contamination.