Determination of Trace Metal Elements in Solid Bitumen with Microwave Digestion by Inductively Coupled Plasma-Atomic Emission Spectrometry

Trace element information in crude oil and bitumen has been applied to oil and gas exploration and geochemical study, but the analysis methods of bitumen are limited and the pretreatment process is tedious. To overcome this, microwave digestion was used to digest the solid bitumen sample and a method was developed for the determination of the 13 trace elements Al, Ca, Fe, K, Mg, Mn, Na, Ti, Ba, Mo, Ni, Sr and V by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The bitumen sample can be digested quickly in closed vessels by microwave at high temperature and pressure. The optimization experiment of the different digestion reagents systems showed that HNO₃-HF digestion system was the best to decompose the solid bitumen. Experimental conditions and sampling weight are discussed. The results show that the method can be used to digest the bitumen sample without loss of volatile elements and contamination in the process of digestion. The recoveries of the method were in the range of 92.2%-101.0% with the precision of less than 5.0%RSD (n=8), and the detection limit was up to 0.05 μg/g. This method can provide a new reference method for the determination of trace metal elements in solid bitumen.