Application of dispersive liquid–liquid microextraction and spectrophotometric detection to the rapid determination of rhodamine 6G in industrial effluents

Abstract

A rapid and effective preconcentration method for extraction of rhodamine 6G was developed by using a dispersive liquid–liquid microextraction (DLLME) prior to UV–vis spectrophotometry. In this extraction method, a suitable mixture of acetone (disperser solvent) and chloroform (extractant solvent) was injected rapidly into a conical test tube containing aqueous solution of rhodamine 6G. Therefore, a cloudy solution was formed. After centrifugation of the cloudy solution, sedimented phase was evaporated, reconstituted with methanol and measured by UV–vis spectrophotometry. Different operating variables such as type and volume of extractant solvent, type and volume of disperser solvent, pH of the sample solution, salt concentration and extraction time were investigated. The optimized conditions (extractant solvent: 300 μL of chloroform, disperser solvent: 3 mL of acetone, pH: 8 and without salt addition) resulted in a linear calibration graph in the range of 5–900 ng mL −1 of rhodamine 6G in initial solution with R 2 = 0.9988 ( n = 5). The Limits of detection and quantification were 2.39 and 7.97 ng mL −1, respectively. The relative standard deviation for 50 and 250 ng mL −1 of rhodamine 6G in water were 2.88% and 1.47% ( n = 5), respectively. Finally, the DLLME method was applied for determination of rhodamine 6G in different industrial waste waters.