Simultaneous determination of triglycerides and cholesterol esters in serum by infrared spectrophotometry

With the use of a high-resolution grating infrared spectrophotometer, it is possible to analyze mixtures of cholesterol esters and triglycerides on the basis of the difference in their ester carbonyl absorption frequencies. In the analysis of serum lipids, the preliminary removal of phospholipids is accomplished by a simple batch adsorption on silicic acid. Infrared absorbance measurements are made on carbon tetrachloride solutions of the unadsorbed lipids, using stationary frequency settings at 1745 cm-' and 1730 cm-' (approximate band peaks of triglycerides and cholesterol esters, respectively). The influence of the minor lipid constituents in this mixture is considered, and the errors from this cause are shown to be negligibly small in most circumstances. The over-all accuracy is estimated to be about *5%.