Quantitative Measurement of Multiple Elements in Micro-Quantities of Crude Oil Using In Situ Analysis by Laser Ablation-ICP-MS

Abstract

Multi-element quantification in small amounts of material and in situ measurements at the micrometre scale are essential aspects of geological sample investigation. A direct and rapid simultaneous multi-elemental determination of metals in crude oil samples was carried out by combining direct laser ablation of the oil inserted in silica capillaries with inductively coupled plasma-mass spectrometry. The accuracy of LA-ICP-MS determination was demonstrated by analysing CONOSTAN reference material oils, certified for multiple elements, and by comparing LA-ICP-MS measurement results with those obtained by ICP-OES using microwave-assisted sample digestion. The results obtained by both methods were in agreement with certified values. The LA-ICP-MS method showed an adequate precision with a mean relative standard deviation of less than 10% for multi-element determination, and was sufficiently sensitive to determine the majority of elements. LA-ICP-MS was also applied to the determination of elements in crude oils of different origins. LA-ICP-MS is a good alternative method allowing the determination of elements in organic fluids (oil and bitumen) in shorter times, involving less material consumption, smaller test portion size and with higher throughput compared with protocols using, for instance, sample digestion. It validates the possible application of metal analysis in hydrocarbon-containing fluid inclusions for metallogenic purposes.