Abstract
Type analysis of crude oil and petroleum products has been studied using a gas chromatograph/time-of-flight mass spectrometer. The use of inert fused silica capillary tube inlet/field ionization (blank tube inlet/FI) is a suitable method for analyzing low boiling point components. Field ionization (FI) and field desorption (FD) methods are classified as soft ionization. Therefore, those ionization methods are used to analyze samples in which the molecular ion is hardly detected on electron ionization, as in the case of hydrocarbons. Type analysis using blank tube inlet/FI, capillary gas chromatography/FI (GC/FI), and FD mass spectra provides useful information, such as the average molecular weight. We examined the composition of crude oil and some petroleum products by type analysis using blank tube inlet/FI, capillary GC/FI, and FD. We carried out type analysis using six series of components. These were CnH2n+2, CnH2n, CnH2n-2, CnHn-4, CnHn-6, and CnHn-8. The averaged molecular weight by FD was much higher than that by blank tube inlet/FI, because it is difficult to measure low boiling point components by FD. In the blank tube inlet/FI method, all components were introduced and ionized. Therefore, this method is much more suitable than other methods for evaluating the composition of crude oil and petroleum products.
