محمد رضا حاج محمدی

An exact, rapid and efficient method for the extraction of rhodamine B (RB) and rhodamine 6G (RG) as well as their determination in three different matrices was developed using magnetic stirring assisted dispersive liquid–liquid microextraction (MSA-DLLME) and HPLC-Vis. 1-octanol and acetone were selected as the extraction and dispersing solvents, respectively. The potentially variables were the volume of extraction and disperser solvents, pH of sample solution, salt effect, temperature, stirring rate and vortex time in the optimization process. A methodology based on fractional factorial design (27-2) was carried out to choose the significant variables for the optimization. Then, the significant factors (extraction solvent volume, pH of sample solution, temperature, stirring rate) were optimized using a central composite design (CCD). A quadratic model between dependent and independent variables was built. Under the optimum conditions (extraction solvent volume = 1050 µL, pH = 2, temperature = 35 ℃and stirring rate = 1500 rpm), the calibration curves showed high levels of linearity (R2= 0.9999) for RB and RG in the ranges of 5-1000 ng mL-1and 7.5-1000 ng mL-1, respectively. Theobtained extraction recoveries for 100 ng mL-1of RB and RG standard solutions were 100% and 97%, and preconcentration factors were 48 and 46, respectively. While the limit of detection was 1.15 ng mL-1 for RB, it was 1.23 ng mL-1 for RG. Finally, the MSA-DLLME method was successfully applied for preconcentration and trace determination of RB and RG in different matrices of environmental waters, soft drink and cosmetic products.