Spectrophotometric Determination of Malachite Green Residue in Water Samples After Preconcentration on Surfactant-Coated Alumina

A new, simple, and reliable method for rapid preconcentration of trace levels of malachite green from water samples is developed using a sodium dodecyl sulfate coated alumina solid phase. The effects of pH, flow rate of sample solution, and foreign ions on the sorption of malachite green have been investigated. Two micrograms of malachite green from 250mL of aqueous phase could be quantitatively extracted into a 500mg of SDS coated alumina. The collected malachite green molecules were eluted with 2mL of acetonitrile and determined spectrophotometrically at 617nm. The detection limit corresponding to three times of the standard deviation of the blank was found to be 3.2 mu gL-1. The proposed method was used for the separation and preconcentration of malachite green with high enrichment factor (about 250) from water samples.