Single drop microextraction in a 96-well plate format: A step toward automated and high-throughput analysis

In this study, an innovative and high-throughput parallel-single-drop microextraction (Pa-SDME) using the [P_6,6,6,14⁺]₂[MnCl₄^2-] magnetic ionic liquid (MIL) as extraction phase is demonstrated, for the first time, in the determination of methylparaben, ethylparaben, propylparaben, bisphenol A, butylparaben, benzophenone and triclocarban from environmental aqueous samples. This experimental setup comprised of a 96-well plate system containing a set of magnetic pins which aided in stabilizing the MIL drops and enabled the simultaneous extraction of up to 96 samples. Using this low-cost experimental apparatus, the sample throughput was lower than 1 min per sample. This novel approach exhibits a number of advantages over classical SDME approaches, particularly in maintaining a stable solvent microdrop and facilitating high-throughput analysis. Experimental conditions were carefully optimized using one-factor-at-a-time and multivariate designs. The optimal conditions employed 5.38 ± 0.55 mg (n = 10) of MIL, a sample volume of 1.5 mL at pH 6, and dilution in 20 μL of acetonitrile. The analytical parameters of merit were determined under the optimized conditions and highly satisfactory results were achieved, with LODs ranging from 1.5 to 3 μg L^-1 and coefficients of determination higher than 0.994. Intraday and interday precision ranged from 0.6 to 21.3% (n = 3) and 10.4-20.2% (n = 9), respectively, with analyte relative recovery in three aqueous samples ranging between 63% and 126%.