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 Green 4) has been determined in its chromatic form in drinking and river water using high-performance liquid chromatography with amperometric detection at a carbon fibre electrode. The limit of detection of the technique 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 cartridges allowed the analysis of malachite green at the 0.28 mu g/l level. The technique was found to be reproducible with a mean relative standard deviation of 5.4 and 3.6% at the 0.25 and 5 mg/l levels, respectively. The application of the technique to the analysis of drinking and river water samples is demonstrated. Typical recoveries from drinking water and river water samples spiked with 1 mu g/l chromatic malachite green were 82 and 41%, respectively. Sorption of malachite green on to suspended organic matter in the water column is discussed. The simultaneous analysis of the chromatic malachite green and its biotransformed leuco form is described.