High detection efficiency isotope ratio analysis using a single focussing ICP magnetic sector mass spectrometer

The IsoProbe is a single focusing magnetic sector ICP source multicollector mass spectrometer. A hexapole collision cell between the ICP source and the magnetic sector analyser reduces the energy spread of ions from the source from 15ev to ion currents of 1E9 cps/ppm are attained, which increases to 1El0 cps/ppm with a CETAC microconcentric desolvating nebuliser. This leads to a total ions per atom detection efficiency of 1% for Pb. The same efficiency is also apparent with laser ablation of NIST glasses and zircons. This high efficiency is equivalent to that reported for the SHRIMP ion microprobe, where in situ Pb isotope ratio measurements have normally been made. We will present the results of the direct, in situ, measurement of lead and hafnium isotope ratios in zircons, and in NIST glasses by laser ablation using a Nd:YAG laser.