A method for giving rapid, reliable, compound-type analyses on distillates from crude oils has been discussed and compared with a classical method for tar acids, tar bases, aromatics, olefins, and paraffins. The new method, using gas chromatographic readout before and after the subtraction of a compound type from a distillate with an internal standard, can be performed on very small samples or dilute solutions. In addition, the new method gives absolute values for saturates, olefins, and aromatics plus polars if polars are defined as those materials staying on silica gel with the aromatics when a nonpolar eluent is used. The determination of tar acids and tar bases has no effect on the saturate and olefin values, only on the aromatic value. Because the extractive determinations using gas chromatographic readout produce results having greater reliability and precision than older methods, the gas chromatographic readout method is useful for compound-type characterization work on polar materials. By comparison of results obtained using a variety of polar-subtractive reagents with those results available from nonaqueous titrimetry or other independent methods, new information on the chemical nature of polar materials can be obtained.
Anal. Instr., V. 10, May 1972, PP. 193-201