RESUMEN
An analytical protocol for rapid and reliable laser ablation-quadrupole (LA-Q)- and multi-collector (MC-) inductively coupled plasma-mass spectrometry (ICP-MS) analysis of Pb isotope ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) in peats and lichens is developed. This technique is applicable to source tracing atmospheric Pb deposition in biomonitoring studies and sample screening. Reference materials and environmental samples were dry ashed and pressed into pellets for introduction by laser ablation. No binder was used to reduce contamination. LA-MC-ICP-MS internal and external precisions were <1.1% and <0.3%, respectively, on both (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios. LA-Q-ICP-MS internal precisions on (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios were lower with values for the different sample sets <14.3% while external precisions were <2.9%. The level of external precision acquired in this study is high enough to distinguish between most modern Pb sources. LA-MC-ICP-MS measurements differed from thermal ionisation mass spectrometry (TIMS) values by 1% or less while the accuracy obtained using LA-Q-ICP-MS compared to solution MC-ICP-MS was 3.1% or better using a run bracketing (RB) mass bias correction method. Sample heterogeneity and detector switching when measuring (208)Pb by Q-ICP-MS are identified as sources of reduced analytical performance.
Asunto(s)
Monitoreo del Ambiente/métodos , Plomo/análisis , Líquenes/química , Espectrometría de Masas/métodos , Suelo , Rayos Láser , Reproducibilidad de los ResultadosRESUMEN
Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al, As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, P, Pb, Ti, V and Zn. The steps involved in the production of the reference material (i.e. collection and preparation, homogeneity and stability studies, and certification) are described in detail.
Asunto(s)
Monitoreo del Ambiente/métodos , Sedimentos Geológicos/análisis , Contaminantes del Suelo/análisis , Metales Pesados/análisis , Valores de Referencia , Suelo/análisis , Oligoelementos/análisisRESUMEN
Juvenile rheumatoid arthritis (JRA) in the Union of Soviet Socialist Republics (USSR) and the United States (USA) shows a remarkable similarity in age of disease onset, subtype onset, frequency, and most laboratory measurements. There is variation in the therapeutic approach with heavier reliance on aspirin in the USA. The evolution of JRA from onset subtype to final subtype over 5 years was the same in both groups and was independent of the type of therapy.