FLOW-INJECTION ANALYSIS FOR TOTAL CHOLESTEROL WITH PHOTOMETRIC DETECTION

The level of total. cholesterol in human blood serum samples is determined by flow-injection analysis. A 70-mu l sample is injected into a phosphate buffer stream, pH 7.0, and led through an enzymatic reactor, which contains cholesterol esterase and cholesterol oxidase immobilized on controlled pore glass. The enzymatically released hydrogen peroxide is detected with 2,2'-azinobis(3-ethylbenzthiazoline-6-su in a peroxidase catalyzed reaction. A linear calibration is obtained in the clinically important range from 0.11 to 8.6 mmol l(-1). The indicator system is compared to the commonly used aminoantipyrine-phenol reagent. The potential interferents studied include bilirubin, triglycerides, haemolyzed serum, glucose, urea, uric acid, and citric acid. The accuracy of the method is established by comparison with a clinically established method based on spectrophotometric endpoint evaluation.