Department of Analytical Chemistry, Agrifood Campus of International Excellence, University of Córdoba, Córdoba, Spain.
Anal Chim Acta. 2012 Jan 4;709:59-65. doi: 10.1016/j.aca.2011.10.016. Epub 2011 Oct 17.
Solvents used in microextraction require high solubilising capability to efficiently extract the target compounds. In this article, nanostructured solvents made up of alkyl carboxylic acids (ACAs) aggregate are proposed for the efficient microextraction of acidic pesticides from natural waters. The target compounds were chlorophenoxy acid herbicides (CPAHs) widely used in agriculture, forestry and gardening (viz. 2,4-D, MCPA, MCPP, 2,4,5-T and MCPB). The supramolecular solvents (SUPRASs) tested were generated from solutions of reverse micelles of octanoic (OcA), decanoic (DeA) and dodecanoic (DoA) acid in THF by the addition of water, which acted as the coacervating agent. The DeA-based SUPRAS was the most efficient extractant for CPAHs; actual concentration factors (ACFs) of 260 for 2,4-D, 290 for MCPA, and 400 for MCPP, 2,4,5-T and MCPB were obtained. The explanation for so high ACFs can be found in the extremely efficient retention mechanisms that the DeA-based SUPRAS provides for CPAHs (i.e. formation of hydrogen bonds and hydrophobic interactions), and the high number of binding sites that it contains (i.e. the concentration of biosurfactant in the SUPRAS was 0.56 mg μL(-1)). Both characteristics permitted to effectively extract the target analytes in a low volume of solvent (about 2 μL of solvent per mL of sample). Others assets of the proposed supramolecular solvent-based microextraction (SUSME) approach included recoveries no dependent on matrix composition, rapidity (sample treatment spent about 15 min), use of low volume of sample (63 mL per analysis) and simplicity (no special lab equipments was needed). Combination with liquid chromatography/ion-trap mass spectrometry [LC-(IT)MS] afforded method quantitation limits for CPAHs within the interval 22-30 ng L(-1). The precision of the method, expressed as relative standard deviation (n=11, [CPAH]=200 ng L(-1)), was in the range 2.9-5.8%. The applicability of the method to the analysis of natural waters was assessed by determining the target analytes in fortified river and underground water samples.
用于微萃取的溶剂需要具有高溶解能力，以有效地萃取目标化合物。在本文中，提出了由烷基羧酸（ACAs）聚集形成的纳米结构溶剂，用于从天然水中高效萃取酸性农药。目标化合物为氯苯氧基酸除草剂（CPAHs），广泛应用于农业、林业和园艺业（如 2,4-D、MCPA、MCPP、2,4,5-T 和 MCPB）。所测试的超分子溶剂（SUPRASs）是由正辛烷（OcA）、正癸烷（DeA）和正十二烷（DoA）在 THF 中的反胶束溶液通过加水形成的，水作为共凝聚剂。基于 DeA 的 SUPRAS 是最有效的 CPAHs 萃取剂；对于 2,4-D 获得了 260 的实际浓度因子（ACF），对于 MCPA 为 290，对于 MCPP、2,4,5-T 和 MCPB 为 400。如此高的 ACF 可以通过 DeA 基 SUPRAS 为 CPAHs 提供的极其有效的保留机制（即氢键和疏水相互作用的形成）以及它所包含的大量结合位点（即 SUPRAS 中生物表面活性剂的浓度为 0.56 mg μL(-1)）来解释。这两个特征使得可以在低体积的溶剂（约 2 μL 溶剂/ mL 样品）中有效地萃取目标分析物。所提出的基于超分子溶剂的微萃取（SUSME）方法的其他优点包括回收率不依赖于基质组成、快速（样品处理耗时约 15 分钟）、使用低体积的样品（每次分析 63 mL）和简单（不需要特殊的实验室设备）。与液相色谱/离子阱质谱联用[LC-(IT)MS]，为 CPAHs 提供了 22-30 ng L(-1) 范围内的方法定量限。该方法的精密度，以相对标准偏差（n=11，[CPAH]=200 ng L(-1)）表示，在 2.9-5.8%范围内。该方法的适用性通过测定加标河水和地下水样品中的目标分析物来评估。
