Automated quantitative gas-liquid chromatography of intact lipis. II. Accuracy, precision and reproducibility of results.
The effect of various factors on the precision and accuracy of the gas chromatographic determination of neutral lipids was studied in the concentration range where the correction factors are dependent on the amount analyzed. The mutual effect of individual components of the neutral lipid spectrum on the recovery was examined. A method is described which provides the stable recovery of the components present at low concentrations, using the addition of high-molecular-weight triglyceride (triarachidin) which does not interfere in the determination of the usual triglycerides. The validity of the correction factors measured with pure compounds was verified by hydrogenation of biological samples of various compositions. Hydrogenation of the sample also solves the problem of the determination of the triglyceride fraction of carbon number 46, which interferes under normal conditions with the determination of the cholesteryl ester fraction of carbon number 47. A method for the standardization of the gas chromatographic determination of neutral lipids is given using pure compounds instead of lyophilized biological samples. Long-term quality control was carried out using synthetic control samples. The results show sufficiently low values of the variation coefficients over the whole period. The values of the variation coefficients measured over an interval of 25 weeks are about 4% for the main components of the neutral lipid spectrum and 6.3% for the components present at concentrations up to 5%. Thw within-day variation for the most neutral lipid fractions and for lipid classes attains a value of 40-75% of the day-to-day variation. The most satisfactory values are obtained for the variation within a single series which amount to less than 2% for all substances except for triglyceride fractions 48 and 54. The correlation of the determination of total cholesterol and triglycerides by gas chromatography and by enzymatic methods shows a very good agreement between the results obtained by the two methods. Using quality control, it is possible to follow the accuracy of the calibration and to demonstrate objectively the necessity for system recalibration.
D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood; D008055:Lipids / Q000097:blood*
D008055:Lipids