SOLID-PHASE EXTRACTION OF PESTICIDE RESIDUES FROM SURFACE WATER USING A LAB-MADE LOWER-RETENTION SORBENT

Solid phase extraction (SPE) is one of the main sample preparation techniques. However, the cost of cartridges and the strong retention of hydrophobic compounds in traditional solid phases are limiting factors for their use. This paper describes the application of lab-made SPE cartridges with low retention material as solid phase, Si(PDAS) - poly(dimethyl-co-alkylmethylsiloxane) thermally immobilized on silica, in the determination of pesticide residues in surface water samples. The extraction method of three pesticides: carbendazim, diurom and methyl parathion in water samples was developed, optimized and validated using Si(PDAS) cartridges and HPLC-UV for quantification. The optimized method required a small organic solvent volume for the elution of pesticides from Si(PDAS), producing a concentration factor of 1000 times and allowing limits of detection like those obtained with hyphenated techniques. The validated method for extraction of pesticides in water samples presented: accuracy, with pesticide recoveries between 70-110%; precision, with RSD < 20%, and; high detectability, resulting in LOQ < 0.4 µg L-1 for all compounds. Si(PDAS) cartridges showed similar efficiency to those commercial C18 for the extraction of pesticides in surface water samples, with additional advantages such as ease, simplicity and low cost of preparation, up to six times cheaper than commercial cartridges.

固相萃取（Solid Phase Extraction，SPE）是主流样品前处理技术之一。然而，传统固相萃取载体的萃取小柱成本高昂，且其对疏水化合物的保留能力过强，这两点成为限制其应用的关键因素。本文报道了以实验室自制低保留固相为填充相的SPE萃取小柱的应用研究：该填充相为热固定于硅胶基质上的聚(二甲基-共聚-烷基甲基硅氧烷)（Si(PDAS)），用于地表水样品中农药残留的检测；研究以Si(PDAS)小柱为萃取介质，结合高效液相色谱-紫外检测法（HPLC-UV）进行定量，开发、优化并验证了针对多菌灵、diurom及甲基对硫磷三种农药的水样萃取方法。经优化后的方法仅需少量有机溶剂即可完成Si(PDAS)小柱上农药的洗脱，实现了1000倍的浓缩倍数，其检测限可与联用技术所得结果相当。经验证的水样农药萃取方法具备以下性能：准确度方面，农药回收率介于70%~110%之间；精密度方面，相对标准偏差（Relative Standard Deviation，RSD）小于20%；且具有优异的检测能力，所有目标化合物的定量限（Limit of Quantitation，LOQ）均低于0.4 µg·L⁻¹。Si(PDAS)小柱用于地表水样品中农药萃取时，其萃取效率与商用C18小柱相当，同时具备制备简便、操作简洁及成本低廉等额外优势，其制备成本仅为商用萃取小柱的1/6左右。