Application of Laser Sampling Microprobe Inductively Coupled Plasma Mass Spectrometry to theIn Situ Trace Element Analysis of Selected Geological Materials

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Abstract
A method is described for the direct solid sampling and analysis of geological materials by laser microprobe inductively coupled plasma mass spectrometry (LAM-ICP-MS). An Nd:YAG laser operated in the Q-switched mode at a fundamental wavelength of 1064 nm was used. Both the sample stage and the laser with its floor-mounted power supply were controlled by a personal computer in a mouse-driven Windows environment. The signal intensity was optimized to the maximum level by adjusting the nebulizer gas flow rate and ion optics using NIST 610 glass. Sample was pre-ablated for a few seconds to remove any surface contamination. NIST 610 or 612 silicate glass was used as a calibration standard and Ca, Ce, Si or Mn were used as an internal standard to correct for signal drift, differences in transport efficiency and sampling yields for different geological materials. Trace element concentrations in apatite, monazite, chromite, olivine, concretion and fused buttons of silicate rock powder were determined in situ with a spatial resolution of 60–150 µm, depending on the materials analysed. Good precision and accuracy and low solid limits of detection were obtained.