Oxidative and Reductive Detection Modes for Determination of Nitrophenols by High-performance Liquid Chromatography with Amperometric Detection at a Boron Doped Diamond Electrode

High performance liquid chromatography with electrochemical detection using a wall-jet arrangement with a working boron-doped diamond film electrode was used for the determination of 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol using reduction and oxidation modes. The optimal conditions for separation at a C18 reverse phase column (125x4 millimeters, 5 micrometers) and amperometric detection of these nitrophenols were determined. Acetate buffer (0.05mole per liter pH 4.7/methanol 58/42, v/v) was chosen as the mobile phase for cathodic detection at the potential of -1.2 volts. The linear dynamic range was 2x10(-6) to 1x10(-4)mole per liter and the limits of detection were from 0.7 to 1.2 micromole per liter. For anodic detection, the mobile phase was 0.05mole per liter phosphate buffer pH 6.75/methanol (65/35, v/v) at a detection potential of +1.3 volts. The linear dynamic range was from 2x10(-6) to 1x10(-4)mole per liter with limits of detection from 0.6 to 1.5 micromoles per liter. The method was successfully employed for direct determination of nitrophenols in drinking and river water with limits of detection between 0.7 and 1.8 micromoles per liter.