In this study, an innovative and high-throughput parallel-single-drop microextraction (Pa-SDME) using the [P6,6,6,14+]2[MnCl42−] 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 highthroughput 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%.

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Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take-make-dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic perspectives of two research groups working on the topic. The article covers the use of unmodified natural materials and the modified ones (although the latter has a less green character) to draw a general picture of the usefulness of the materials.Separations 2020, 7, 2 2 of 22 principle identifies one of the trends of current research in analytical sciences, it is difficult to be applied when complex samples containing the analytes at very low concentrations are processed. In such scenarios, the simplification of the sample treatment and the reduction of the sources applied (reagents, energy) can be a more practical objective, at least currently. Microextraction techniques fulfill the latter criteria [8], and they are considered among the greenest sample treatment techniques [9].Microextraction techniques have evolved in the last decade following some key trends. Among them, the development of new extraction phases can be highlighted, considering the context of this review article. In this evolution, the tenth (use of renewable resources) and eleventh (replace or remove toxic reagents) principles of GAC are especially relevant [7]. In the liquid microextraction context, environmentally friendly solvents [10,11] such as CyreneTM [12] and deep eutectic solvents [13] are clear examples of this progress.The paradigm of our production system, which up to now has been based on a linear "take-make-dispose" model, is progressively changed to a circular model [14] where reusing, repairing, refurbishing, and recycling appear as key terms. The use of surpluses of natural products as raw materials for the preparation of new sorbents is an interesting contribution of analytical chemistry for changing the production model. This review article, which combines the vision of two research groups working in the topic, tries to draw the general picture of the potential of natural products for the synthesis of new sorptive phases in solid phase extraction and solid phase microextraction. The article will cover strategies with different green characterist...

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