DETERMINATION OF LEAD IN MICROLITER AMOUNTS OF WHOLE-BLOOD BY STRIPPING POTENTIOMETRY

Lead in whole blood is determined using a commercial potentiometric stripping analyzer in combination with a portable personal computer and a new electrode design permitting rotation of the sample. A 70 muL blood sample is added to 200 muL distilled water contained in a disposable test tube. After mixing, 400 muL of a matrix-modifying solution containing hydrochloric acid, mercury (II) ions, Triton X-100, and bismuth (III) as an internal standard, is added to the sample which is then transferred to the sample holder. Lead amalgam is deposited on the glassy carbon electrode by means of a pulsed potential cycle for 3 minutes after which lead is reoxidized by means of a constant current. The complete electroanalytical procedure, including result evaluation by means of the internal standard, and graphical display is under computer control. For ca. every 15th sample, the instrument is recalibrated, if necessary using two whole blood standards. The relative precision is ca. 10% and the detection limit 3.5 mug/L. The stripping potentiometry results agree well with the results obtained by inductively coupled plasma mass spectrometry in the analysis of whole blood from individuals occupationally exposed to lead and with the results obtained by graphite-furnace atomic spectroscopy in the analysis of whole blood from 141 school children.