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A flow-injection analytical (FIA) system was developed for the determination of cholesterol concentrations based on enzymatic reactions that occurred in a cholesterol oxidase (CHOx)-immobilized, fused-silica capillary followed by electrochemical detection. The production of hydrogen peroxide from cholesterol in an enzymatic reaction catalyzed by CHOx was subsequently oxidized electrochemically at an electrode. Our FlA system demonstrated its cost-effectiveness and utility at an applied potential of 0.6 V (vs. Ag/AgCl), a flow rate of 100 μL/min and, under optimal conditions, the resulting signal demonstrated a linear dynamic range from 50 μM to 1.0 mM with a limit of detection (LOD) of 12.4 μM, limit of quantification (LOQ) of 44.9 μM, and the coefficient of variation of 5.17%. In addition, validation of our proposed system using a reference HDL-cholesterol kit used for clinical diagnosis suggested our FIA system was comparable to commercial kits for the determination of the cholesterol incorporation amount in various aqueous liposomal suspensions. These good analytical features achieved by FIA could make the implementation of this methodology possible for on-line monitoring of cholesterol in various types of samples.

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