Accurate and precise determination of lead isotope ratios in clinical and environmental samples using inductively coupled plasma source mass spectrometry

Methods are described for the accurate and precise determination of lead isotope ratios in human tissues and environmental samples including blood, teeth, paint, lead plumbing and UK petrol vehicle exhaust residue. Over a four-month period 33 measurements of the 206Pb : 207Pb ratio in a quality control blood sample with a known lead isotopic composition gave a between-batch relative standard deviation of 0.35% with an accuracy of –0.09% relative to thermal ionisation-isotope dilution mass spectrometry (TI-IDMS). This performance was sufficient to allow source apportionment in instances of excessive lead exposure in some children for whom deviations in the 206Pb : 207Pb ratio of up to 2.3% were observed.