Development of high-sensitive and rapid measurement of lead isotopic ratio for environmental fate analysis

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Lead isotopic composition is considered to be a useful means for discriminating the source of lead in the environment. Present author established a nondestructive as well as simple and accurate method for the measurement of lead isotopic ratio by means of secondary mass spectrometry(SIMS) and laser ablation inductivity coupled plasma mass spectrometry(LA/ICP-MS). The mixture of lead sulfide prepared from NIST SRM 981 Lead with graphite powder was used as a standard reference sample for the isotope measurement. The standard reference sample thus prepared and the real sample such as vehicle exhaust particulates, urban particulate matter and pond sediment were pressed into films for the measurement respectively. A pair of films of standard sample and real sample was irradiated alternately by the primary 02+ ion beam and laser as so to measure the isotopic ratios under the same instrumental condition. A Nd:YAG laser was used for ablating sample surface in Q-switched mode. Measured values of samples were corrected by the certified value of NIST standard reference sample. Corrected values of isotopic ratios of some environmental samples were in good agreement with those measured by TIMS and ICP-MS. When measuring the isotopic ratio of airborne particulate on the glass-fiber filter directly, it is need to prepare the glass-fiber filter standard sample for correcting the measuring value of airborne particulate from an ambient air. The glass-fiber standards samples impregnated with lead nitrate and adsorbed lead sulfide were prepared. Corrected value of isotopic ratio of NIST 1648 urban particulate matter was in good agreement with known value.