Comparison of electrochemiluminescence and amperometric detection of lipid hydroperoxides

Abstract

Amperometric measurement and electrochemiluminescence (ECL) were used for the detection of lipid hydroperoxide in aqueous solutions. In the amperometric measurements, lipid hydroperoxide was detected by its oxidation current at a glassy carbon electrode in a flow cell (ECO method). This oxidation occurred at a very positive potential (1.10 V vs. SCE). In the ECL method, luminol, which is oxidized at a less positive potential than lipid hyperoxide, was electrochemically oxidixed to the excited intermediate (diazaquinone) on the electrode, then the oxidized luminol reacted with lipid hydroperoxide which emitted light. The ECO and ECL methods were compared at both glassy carbon and platinum electrodes in a flow-injection system with phosphate buffer (pH 7.4)-30% acetonitrile carrier solution for measurement of lipid hydroperoxide. Uric acid, ascorbic acid and tocopherol, which are present in blood samples, interfered with the ECL signal. In the ECO method, only uric acid and ascorbic acid interfered with the signal. The detection limit, relative standard deviation (R.S.D.) at the detection limit and signal-to-noise ratio ( S/N) were as follows: ECO at a glassy carbon electrode, 0.05 nmol with R.S.D. 4.9% ( n = 5) and S/N 1.36; ECL at a glassy carbon electrode, 0.3 nmol with R.S.D. 13% ( n = 5) and S/N 1.5; and ECL at a platinum electrode, 0.1 nmol with R.S.D. 5.3% ( n = 5) and S/N 2.5.