High Precision Pb Isotope Determination by Using 207Pb-204Pb Double Spike Revisited

Abstract

A method for getting high quality Pb isotope ratio analysis using 207Pb-204Pb double spike method has been developed at Scripps Institution of Oceanography (SIO), which corrected the mass fractionation effects during small amount Pb loading isotopic analysis by thermal ionization mass spectrometry (TIMS), with the minimum amount of 8×10-9g Pb per load. The double spike method effectively improves in both precision and accuracy without recourse to excessively rigorous loading or run conditions. Over a period of fifteen months accuracy double spike tested for Pb standard SRM981 in SIO isotope laboratory, an external precision of ±0.0038、±0.0040、±0.0122 (2σ, n=53) was obtained for 206Pb/204Pb, 207 Pb/204Pb and 208Pb/204Pb rations, although the small amount Pb loading, which present a same excellent accuracy and external precision as other laboratories reported. Therefore, this method is superior to precise and accurate isotope analyses of low level Pb concentration geological and environmental samples, and will be a highly powerful tool in the future of earth sciences and environmental sciences.