Electrothermal atomization atomic absorption spectrometry for the determination of lead in urine: results of an interlaboratory study

Results of an interlaboratory study are reported for the determination of l ead in urine. Two levels of a lyophilized material containing biologically- bound lead were prepared using pooled urine obtained from lead-poisoned chi ldren undergoing the CaNa(2)EDTA mobilization test. The materials were circ ulated to a group of reference laboratories that participate in the 'New Yo rk State Proficiency Testing Program for Blood Lead'. Results of the initia l round-robin gave all-method consensus target values of 145 +/- 22 mu g/l (S.D.) for lot 17 and 449 +/- 43 mu g/l (S.D.) for lot 20. The interlaborat ory exercise was repeated some 5 years later and consensus target values we re re-calculated using the grand mean (excluding outliers) of results repor ted by laboratories using electrothermal atomization atomic absorption spec trometry (ETAAS). The re-calculated target values were 139 +/- 10 mu g/l (S .D.) and 433 +/- 12 mu g/l (S.D.). The urine reference materials were also analyzed for lead by several laboratories using other instrumental techniqu es including isotope dilution (ID), inductively coupled plasma (ICP) mass s pectrometry (MS), flame atomic absorption with extraction, ICP-atomic emiss ion spectrometry, ID-gas chromatography MS and flow injection-hydride gener ation AAS, thus providing a rich source of analytical data with which to ch aracterize them. The materials were also used in a long-term validation stu dy of an ETAAS method developed originally for blood lead determinations th at has since been used unmodified for the determination of lead in urine al so. Recently, urine lead method performance has been tracked in a proficien cy testing program specifically for this analysis. In addition, a number of commercial control materials have been analyzed and evaluated. (C) 1999 El sevier Science B.V. All rights reserved.