HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF THE TRIPHENYLMETHANE DYE, MALACHITE GREEN, USING AMPEROMETRIC DETECTION AT A CARBON-FIBER MICROELECTRODE

The triphenylmethane dye, malachite green (Colour Index C.I. Basic Gre en 4) has been determined in its chromatic form in drinking and river water using high-performance liquid chromatography with amperometric d etection at a carbon fibre electrode. The limit of detection of the te chnique was 0.07 mg/l and the linear range extended from 0.07-10 mg/l. The use of a 250-fold preconcentration on solid-phase extraction cart ridges allowed the analysis of malachite green at the 0.28 mu g/l leve l. The technique was found to be reproducible with a mean relative sta ndard deviation of 5.4 and 3.6% at the 0.25 and 5 mg/l levels, respect ively. The application of the technique to the analysis of drinking an d river water samples is demonstrated. Typical recoveries from drinkin g water and river water samples spiked with 1 mu g/l chromatic malachi te green were 82 and 41%, respectively. Sorption of malachite green on to suspended organic matter in the water column is discussed. The sim ultaneous analysis of the chromatic malachite green and its biotransfo rmed leuco form is described.