Hydrocarbon group type analyzer system for the rapid determination of saturates, olefins, and aromatics in hydrocarbon distillate products

A dielectric constant (DC) detector for high-performance liquid chromatography (HPLC) is the basis of a rapid and accurate hydrocarbon group type analysis. This novel method can determine saturates, olefins, and total aromatics in hydrocarbon liquids with distillation end points (ASTM D 2887) of at least 400 /sup 0/C. The HPLC separation is achieved by using a single, olefin-selective column, a backflush valve, and Freon 123 as the mobile phase. The DC detector ensures a genuine uniformity of response (less than 2.5% relative standard deviation) for each hydrocarbon group type independent of the carbon number distribution of the sample. Unity response factors are sufficient. On the basis of complex solutions of hydrocarbon standards, the accuracy for each structural group type is within 1% absolute. The chromatographic limit of detection is less than 0.5 vol % (800 ng) for the last eluting hydrocarbon group, i.e., the olefins.