CPE-Scanometry as a new technique for the determination of dyes: application for the determination of fast green FCF dye and comparison with spectrophotometric results

In this study, a new, simple, fast and inexpensive method, CPE-Scanometry, is introduced and applied for the determination of dyes. The method is based on the CPE of the analyte from the aqueous solution, diluting the extracted surfactant-rich phase with a suitable solvent to 500 mu L and transferring an appropriate volume to a Plexiglas (R) cell. The cells containing the analyte solution were scanned with a scanner, then the color of each cell was analyzed, with software written in Visual Basic (VB 6), to obtain the red, green and blue values. The cells were built by creating holes in the Plexiglas (R) sheet. The proposed method was used to determine fast green FCF, an anionic triarylmethane dye. Effective parameters on the extraction efficiency such as the pH of the system, the concentration of the dye and surfactant, equilibration temperature and time, were investigated and optimized. The results and the figure of merit of the proposed method were comparable with those of CPE-Spectrophotometry. Under the optimal conditions, the calibration curve was linear in the range of 0.03-1.0 mg L-1 for CPE-Scanometry and 0.01-1.0 mg L-1 for CPE-Spectrophotometry. The preconcentration and enhancement factors for the proposed method are 30 and 12.62, respectively, while for CPE-Spectrophotometry the values obtained are 15 and 3.35. The detection limit of the two methods was compared. In addition, the effects of foreign species, including cations, anions and dyes, were investigated. The method was successfully applied to the determination of the fast green FCF in several aqueous solutions.