Microanalysis of solid samples by laser ablation and total reflection X-ray fluorescence

Abstract

Total reflection X-ray fluorescence (TXRF) was applied in the analysis of metallic and ceramic materials after LA. Sample material was evaporated by the focussed radiation of a pulsed Nd: YAG laser and collected directly on a quartz or Plexiglas disc commonly used as a sample carrier for TXRF. Iron–Cr and Cu–Zn binaries, a high-alloy steel sample, and a high-temperature superconducting ceramic (YBa₂Cu₃O_6.9) were chosen for analysis. Only microgram quantities of sample material were removed per laser shot, and only a few nanograms of sample were deposited on the sample carrier. This minute amount was sufficient for TXRF analysis. The mass of individual elements detected by TXRF was at the pg-level, so that a mass fraction in the order of 1 mg g^–1 could be determined. Quantification was achieved by addition of an internal standard. Accurate results were obtained after a single laser shot of the deposits of the binary samples, the steel sample and the ceramic material. Deviations from the correct composition were only observed for the Cu–Zn binaries when using multiple laser shots. The combination of LA with TXRF detection enables ultra-microanalysis of solids without laborious sample preparation steps. By repetitive laser pulses upon neighbouring spots a microdistribution analysis may become possible with a lateral resolution of about 10 µm.