A new method for the simultaneous determination of trace amount of malachite green and crystal violet from aqueous solution by spectrophotometry after cloud point extraction using derivative ratio spectrophotometry has been proposed. The wavelength of absorption of malachite green and crystal violet is 639,476 nm. Linearity was obeyed in the range of 1. 0 × 10^- 8~ 1. 0 × 10^- 6mol / L with limit of detection of 3. 93 × 10^- 9mol / L and 4. 96 × 10^- 9mol / L,respectively. The relative standard deviation was less than 4. 08% and 4. 31%,resp...
