Abstract
On-line column switching high-performance liquid chromatography (HPLC) with dielectric constant detection (DCD) can separate and accurately quantify the volume fraction of total cycloparaffins in gasolines and kerosenes having distillation endpoints (ASTM D 2887) of at least 300°C. The three hydrocarbon group-types reported are: acyclic paraffins, cycloparaffins, and unsaturates, i.e., aromatics plus olefins. The HPLC—DCD separations are achieved using an “unsaturate-selective” column, two “naphthenic-selective” columns, two six-port switching valves, and Freon 123 as the mobile phase. Incorporation of one or two additional naphthenic-selective columns could extend the range of samples that can be analyzed to include diesel fuels. The dielectric constant detector ensures a genuine uniformity of response [relative standard deviation < 2.5%] for each hydrocarbon group type independent of the carbon number distribution of the sample. Unity response factors are sufficient for accurate quantitation. On the basis of complex solutions of hydrocarbon standards, the accuracy for each structural group type is within two percent absolute. The chromatographic limit of detection for naphthenes is less than 4.0 vol. % ( ca.40 μg) for a kerosene fuel containing a wide carbon number distribution of both mono- and di-cycloparaffins. Sample turnaround time is approximately 40 min.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call