Cholesterol ester, quantitative determination

The enzymatic method for determination of cholesterol Is based on that of Klose et al. [15], as modified by Leon and Stasiw [16]. It involves the use of cholesterol stearase to hydrolyse the cholesterol esters In serum to free cholesterol, which Is oxidized to HzCte that In turn forms a qulnonelmlne dye. The reaction is quantitative, so the concentration of the dye formed Is directly proportional to that of cholesterol In the sample. Figure 14.4 Illustrates the function of the SMAC channel used for the determination, in which the reagent stream (cholesterol oxidase, cholesterol stearase, peroxidase, phenol and 4-aminophenazone), the sample and some air are aspirated by the pump and, after mixing in reactor Ri, are Incubated for 4 min in a bath at 37 C, after which the dye Is extracted Into alcohol and sent to the detector, where Its absorbance Is measured at 525 nm. The aqueous phase from the extraction and the cell waste are aspirated by pump P2. The method has fewer and less serious interferences than Its non-enzymatic counterpart. 

Cholesterol esters and triglycerides have been determined in serums by infrared methods. Biliary and renal calculi ate quite readily analyzed from infrared spectra. Sometimes it is necessary to determine body water content, and this can be done by the use of DjO, and quantitating the deuterium by means of infrared spectroscopy. 

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