Monosegmented flow-analysis of serum cholesterol.

A monosegmented flow system is designed for enzymatic spectrophotometric determination of cholesterol in blood serum. The sample (4.5 microliters), enzymatic reagent (150 microliters) and an air plug (100 microliters) are simultaneously inserted into a carrier stream buffered to pH 7.4 (potassium dihydrogenphosphate). In order to avoid the step of air removal, a relocating detector was used. This system handles about 42 samples per hour, yielding precise results (R.S.D. usually < 3.0%). Sensitivity is 46 mAU 1/mmol (mAU stands for milliabsorbance units), being the method linear up to 10.3 mmol/l cholesterol. Accuracy was assessed by running 30 samples already analysed by a conventional procedure: no statistical difference between methods was found at the 95% confidence level.