LIQUID-CHROMATOGRAPHY SERIES DUAL-ELECTRODE AMPEROMETRIC DETECTION FOR AROMATIC NITRO-COMPOUNDS

A new design of dual-electrode electrochemical detector for liquid chromatography is described utilizing two series generator/detector electrodes. The detector developed is based on the larger electrode area design compared with commercial ones and has higher electrolytic efficiency, which lead to a higher detection sensitivity when in a reductive-oxidative series detection mode. Analytes are first reduced at the upstream electrode and the reaction products are then detected by oxidation at the downstream electrode. So, the influence of dissolved oxygen and trace amounts of heavy metals in the mobile phase and sample is eliminated. Thus, exhaustive removal of dissolved oxygen before analysis is not required, and the method can be easily automated. The technique is tested on seven aromatic nitro compounds. Under the optimized conditions, the assay is linear in a concentration range of 2.0 x 10(-7) to 4.0 x 10(-5) g/mL and has low detection limits of 1.0 to 2.0 ng using a 10 mu L sample. The largest standard deviation was 5.2%. The recovery of the detection of water samples was 93 to 107%.