Robust ionic liquid against high concentration of salt for preconcentration and determination of rhodamine B

Abstract Resistant ionic liquid-based dispersive liquid–liquid microextraction (IL-based DLLME) method is described for sensitive determination of trace amounts of rhodamine B in aqueous samples containing very high salt concentrations by fiber optic-linear array detection spectrophotometry (FO-LADS). The method is based on the DLLME of rhodamine B from aqueous solution using ionic liquid. The robustness of microextraction system against high salt concentration (up to 40%, w/v) is increased by introducing a common ion of the ionic liquid into the sample solution. The extracted rich phase is diluted with acetone, and its absorbance is measured at 556 nm by a spectrophotometer. The effects of different operating parameters such as concentration of salt, pH, effect of IL and disperser solvent and NaPF 6 on the DLLME of rhodamine B were studied in details. Under optimum conditions a linear calibration graph in the range of 5–100 μg L −1 of rhodamine B in the initial solution with R 2  = 0.9993 ( n  = 10) was obtained. Detection limit based on three times the standard deviation of the blank (3 S b ) was 1.05 μg L −1 ( n  = 10) and the relative standard deviation (R.S.D.) for 50 μg L −1 of rhodamine B was 1.3% ( n  = 10), respectively. The proposed method was successfully applied for the determination of rhodamine B in various samples.