AMPEROMETRIC DETERMINATION OF HIGH-DENSITY-LIPOPROTEIN CHOLESTEROL USING POLYETHYLENE GLYCOL-MODIFIED ENZYMES AND A PEROXIDASE-ENTRAPPED ELECTRODE

A peroxidase-entrapped and ferrocene-embedded carbon paste (POD-Fc-CP) electrode allows a highly sensitive detection of H2O2 at levels as lo w as 10 nmol/L with practically no interference by coexisting substanc es, turbidity or coloration of samples. The electrode was applied to t he amperometric determination of high-density lipoprotein (HDL)-choles terol in a very small volume (1-2 mu L) using polyethylene glycol (PEG )-modified cholesterol esterase and cholesterol oxidase without prior precipitation or separation of HDL. PEG-modified enzymes exhibit a sel ective activity toward HDL-cholesterol in the presence of dextran sulp hate and MgCl2 to generate H2O2 The HDL-cholesterol concentrations of human serum samples determined by this method showed a good correlatio n with those determined by an ordinary spectrophotometric method using PEG-modified enzymes and peroxidase or by a conventional precipitatio n method.