Automated quantitative gas--liquid chromatography of intact lipids. I. Preparation and calibration of the column

A method for quantitative gas chromatographic determination of plasma lipids (free cholesterol, cholesteryl esters and triglycerides) in the low concentration range is described. This method permits a determination of not only the lipid classes mentioned above, but also their fractions according to molecular weight, down to 10 ng, without previous derivatization. Special attention was devoted to the preparation of columns with high efficiency and minimal losses of the test substances. The best results were obtained with a glass column 0.5 m x 2.0 mm I.D., packed with 1% OV-1 on Gas-Chrom Q (100--120 mesh). The processing of results is fully automated, using an MDS-2400 computer and includes the calculation of a non-linear calibration plot for each substance analyzed, accuracy control of the measured values, tabulation of the fwr values and the calculation for analyses of biological samples. For the calibration, the pure substances were used at 15 concentrations within a range of 10--1000 ng. The coefficient of variation calculated from 20 duplicate measurements of the calibration mixture did not exceed 5% for any component in the interval from 10 to 100 ng or 3% within range from 100 to 1000 ng.