A new technique to determine element amounts down to femtograms in dust using femtosecond laser ablation-inductively coupled plasma-mass spectrometry

摘要

Atmospheric dust has a substantial impact on climate, and climate in turn affects the dust flux and origin. Knowing its composition helps to determine dust sources and climate processes. We have therefore determined 46 major and trace elements in dust samples, using in-situ 200 nm-femtosecond laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Very small test portions of 4-7 μg were enough to enable analyses down to detection limits of femtograms and ng g~(?1), respectively. The data agree within 40 to 15% with the reference values for test portions of 1 to 100 μg, respectively. The femtosecond laser results are compared to those obtained using a 213 nm nanosecond laser, which show the advantages of the femtosecond laser, such as the ability to use non-matrix-matched calibration, reliable measurements of volatile elements, and smaller quantities of material ablation with similar results for the repeatability. The technique is especially useful for measurements of small amounts of dust on filters, and for 2D-distribution maps of selected elements to identify minerals or contamination. To demonstrate the applicability, five dust samples from Niger and Chad, in the Sahara zone, were analyzed. The samples are characterized by enrichment in light REEs and a distinct Eu anomaly, with surface soils as their source.