Determining isotope ratios using laser ablation sampling in air with MC-ICPMS

Isotope ratio determination in solids sampled in air under atmospheric pressure using laser ablation with direct introduction into an ICPMS was carried out. The results obtained on the metal brass, and two minerals galena and zircon are reported in this manuscript. The samples were ablated in air and the laser-generated aerosol was aspirated into a gas exchange device (GED), where the air was replaced with Ar and transported into a multicollector-inductively coupled plasma mass spectrometer (MC-ICPMS). To demonstrate the capability of this sampling method, the results were compared to the results obtained using conventional laser ablation (LA)-MC-ICPMS in helium in a sealed cell. Data show that comparable in-run (0.03–1.61%) and external (0.002–0.254%) precisions can be obtained. The accuracy (0.000–0.192%) of both methods was also comparable. However, the atmospheric sampling method gave lower intensities, by up to a factor of 5. Visualization of the aerosol extraction indicates that some material was lost prior to gas exchange. However, this method is suitable for isotopic determination of bulk materials for samples which are too large to fit into an ablation cell or too valuable to be cut into smaller pieces.