High‐Resolution LA‐ICP‐MS for Accurate Determination of Low Abundances of K, Sc and Other Trace Elements in Geological Samples

Abstract

Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was used to determine K, Sc, Ti, V, Cr, Mn, Co, Ni and Zn in geological samples. Because the isotopes of these elements and the internal standard element (Ca) often have interferences from molecular ions when determined using quadrupole or sector‐field ICP‐MS in low mass resolution mode, ion intensities were measured at a high mass resolution of 4000. We investigated dynamic element fractionation, type and abundance of molecular ions using different geological reference materials. Highly resolved mass spectra were especially important for accurate low‐abundance measurements. As a result, maximum “critical” concentration limits for each isotope were obtained, where a mass resolution of 4000 was necessary for reliable LA‐ICP‐MS analysis. To test the LA‐ICP‐MS technique, different international reference material glasses and powdered rock reference materials were analysed. Rock powders were fused to glass beads using an Ir‐strip heater. Nearly all concentration values for the reference materials agreed with the reference values at the 95% confidence level. To demonstrate routine LA‐ICP‐MS analysis at a mass resolution of 4000, trace element data for Hawaiian basalts are also presented.