DIRECT DETERMINATION OF OXYGEN BY HPLC .1. BASIC PRINCIPLES OF A SENSITIVE AND SELECTIVE OXYGEN SENSOR

The basic principles of a novel, versatile, sensitive, and selective o xygen-sensing assay are presented in this paper, For the first time, l iquid chromatography with electrochemical detection (at the hmde) has been used for the determination of oxygen. All factors concerning opti mization of the chromatographic separation conditions and electrochemi cal detection with respect to direct determination of oxygen even in c omplex biological samples are discussed. Due to the combination of a c hromatographic technique with amperometric detection, a high selectivi ty can be achieved. A direct and linear relationship between the oxyge n concentration in the sample and the reduction current was verified i n a large concentration range from saturation down to trace level oxyg en concentrations, The novel oxygen-sensing assay provides a much high er sensitivity compared to conventional oxygen sensors, In principle, O-2 concentrations down to 4.5 x 10(-9) mol L-1 O-2 (corresponding to a signal-to-noise ratio of 3) can be detected, Precision was determine d by repeated measurements (n = 6) of air-saturated solutions (2.5 x 1 0(-4) mol L-1 O-2, 20 degrees C, 920 mbar) which yielded relative stan dard deviations of lower than 0.2%.