Application of Secondary Ion Mass Spectrometry to the Measurement of Lead Isotope Ratio in Individual Particles

The capability of secondary ion mass spectrometry (SIMS) for lead isotope ratio measurements of individual particles has been demonstrated by measuring lead‐containing particles in three kinds of environmental certified reference materials (CRMs): urban particulate matter, vehicle exhaust particulates, and coal fly ash. After mounting of the sample onto a glassy carbon carrier, the particles containing lead were identified and located by an electron probe micro‐analyzer equipped with wavelength dispersive x‐ray spectrometers. The isotope ratios of 207Pb/206Pb and 208Pb/206Pb for the individual particles on the carrier were determined by SIMS. The relative standard deviations of the lead isotope ratios were less than 1.6% for all particles measured. It was demonstrated that the results of the lead isotope ratios were clearly distinguished among the three samples. Moreover, the particles in the vehicle exhaust particulate sample were classified into two groups according to lead isotope ratios. The results indicated that the present SIMS technique can provide detailed information with regard to the origin and the transportation of individual particles, which is difficult to obtain by conventional bulk analysis techniques such as inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry.