An adsorptive stripping voltammetric method for the determination of malachite green (MG) in fish farm water has been developed. Initial studies were made on the cyclic voltammetric behaviour of malachite green at a glassy carbon electrode in 0.1 M phosphate buffer over the pH range 2 to 10. The redox behaviour observed for malachite green was verified by both data analysis of malachite green its reduction product, leucomalachite green (LMG). Furthermore, leucomalachite green was found not to interfere with the determination of malachite green at pH 7.4, the optimum pH for malachite green determination. As a result, further studies were undertaken to exploit this as the basis of an adsorptive stripping voltammetric method for the trace determination of malachite green in fish farm water samples. The conditions necessary including voltammetric waveform, accumulation potential and time were investigated and optimised. Using differential pulse voltammetry the calibration plot was found to be linear from 0.2 µM to 1.2 µM of malachite green with a sensitivity of 0.8311 µA/µM. Using the method of multiple standard addition, fish farm water samples fortified with 0.5 µM and 0.75 µM malachite green were found to give mean percentage recoveries of 78.79 % and 87.20 % respectively (the coefficient of variation is 2.07 % and 1.45 %). Therefore, the performance data suggests that the method is reliable at the concentrations examined in this study and that a rapid, simple, economical and precise method of monitoring of malachite green in fish farm water and aquaculture applications is possible.
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