Determination of Trace Metal Elements in Crude Oils by Microwave Digestion-Inductively Coupled Plasma-Mass Spectrometry Assisted with Organic Solvent

A method for determination of V, Cr, Fe, Ni, Cu, Zn, Mo Co, Pb, etc in different crude oils was established by inductively coupled plasma-mass spectrometry assisted with organic solvent microwave digestion. The oil sample was digested by microwave using HNO₃-H₂O₂ as oxidant after dispersing in organic solvent (CH₂Cl₂). The results showed that the detection limits of the method reached ng/L level for sixteen elements. The linear correlation of the method was preferable with the correlation coefficient of better than 0.9995. The recoveries of the method were in the range of 92%~110% with the precision of less than 5.0%RSD (n＝3). The ratios of w(Ni)/w(V) and w(Fe)/w(V) were distinct in different crude oil samples from oversea and domestic, and the index can be used to the cluster analysis for differencing the crude oil samples.