Solid-phase extraction (SPE) is a widely-used and very well-established sample preparation technique for liquid samples. An area of on-going focus for innovation in this field concerns the development of new and improved SPE sorbents that can enhance the sensitivity and/or the selectivity of SPE processes. In this context, mixed-mode ion-exchange sorbents have been developed and commercialised, thereby allowing enhanced capacity and selectivity to be offered by one single material. The ion-selectivity of these materials is such that either anion-exchange or cation-exchange is possible, however one limitation to their use is that more than one sorbent type is required to capture both anions and cations. In this paper, we disclose the design, synthesis and exploitation of a novel SPE sorbent based on microporous polymer microspheres with amphoteric character. We show that it is possible to switch the ion-exchange retention mechanism of the sorbent simply by changing the pH of the loading solution; anion-exchange dominates at low pH, cation-exchange dominates at high pH, and both mechanisms can contribute to retention when the polymer-bound amphoteric species, which are based on the α–amino acid sarcosine (N-methylglycine), are in a zwitterionic state. This is an interesting and useful feature, since it allows distinctly different groups of analytes (acids and bases) to be fractionated using one single amphoteric sorbent with dual-functionality. The sarcosine-based sorbent was applied to the SPE of acidic, basic and amphoteric analytes from ultrapure water, river water and effluent wastewater samples. Under optimised conditions (loading 100 mL of sample at pH 6, washing with 1 mL of MeOH and eluting with an acidic or basic additive in MeOH) the recoveries for most of the compounds were from 57% to 87% for river water and from 61% to 88% for effluent wastewater. We anticipate that these results will lay the basis for the development of a new family of multifunctional sorbents, where two or more separation mechanisms can be embedded within one single, bespoke material optimised for application to challenging chemical separations to give significant selectivity advantages over essentially all other state-of-the-art SPE sorbents.

固相萃取（SPE）是一种用于液体样品的广泛使用且非常完善的样品制备技术。该领域中持续创新的重点领域是开发新的和改进的SPE吸附剂，该吸附剂可以提高SPE工艺的灵敏度和/或选择性。在这种情况下，已经开发出混合模式的离子交换吸附剂并将其商品化，从而可以通过一种单一的材料提供更高的容量和选择性。这些材料的离子选择性使得可以进行阴离子交换或阳离子交换，但是对它们的使用的一个限制是要捕获阴离子和阳离子都需要一种以上的吸附剂。在本文中，我们将披露设计，基于两性微孔聚合物微球的新型SPE吸附剂的合成与开发。我们表明，仅通过改变加载溶液的pH值就可以改变吸附剂的离子交换保留机制。阴离子交换在低pH值下占主导地位，阳离子交换在高pH值下占主导地位，当基于聚合物的两性物质（基于α-氨基酸肌氨酸（ñ-甲基甘氨酸），处于两性离子状态。这是一个有趣且有用的功能，因为它允许使用一种具有双重功能的单性两性吸附剂对截然不同的分析物组（酸和碱）进行分馏。将基于肌氨酸的吸附剂应用于超纯水，河水和废水样品中的酸性，碱性和两性分析物的SPE。在优化的条件下（加载100 mL的pH 6样品，用1 mL的MeOH洗涤，并用MeOH中的酸性或碱性添加剂洗脱），大多数化合物的回收率在河水中为57％至87％，从61％为61％。 ％至88％的废水。我们预计这些结果将为开发新的多功能吸附剂系列奠定基础，在该系列产品中，两个或多个分离机制可以嵌入到一个单一的吸附剂中，