CPE-Paptode as a new technique for determination of dyes: application for determination of acid red 151

In the present study, a new method for monitoring the signal after cloud point extraction (CPE) of dyes is introduced. The CPE-Paptode method was used to determine acid red 151, as an anionic dye. The method is based on the CPE of dye from aqueous solution, using Triton X-114, diluting the extracted surfactant-rich phase with ethanol and measuring the RGB parameters by special software written in visual basic (VB 6). Parameters, such as pH of the system, the concentration of the dye and surfactant, equilibration temperature and time, as effective parameters on the extraction efficiency and the determination of the dye, were investigated and optimized. Under the optimal conditions, the calibration curve was linear in the range of 0.5-19.0 mg L-1. Preconcentration of a 15 mL sample gave an enhancement factor of 13.2 and a detection limit of 0.32 mg L-1. In addition, the effects of some foreign species including cations, anions and dyes were investigated. The method was successfully applied to the determination of the acid red 151 content in aqueous solution. The results and the figure of merits of the proposed method were comparable with those of CPE-spectrophotometry.