改性多壁碳纳米管固相萃取测定农产品中苯氧羧酸类除草剂残留

通过对多壁碳纳米管(MWNTs)的表面酸氧化、表面共价接枝功能化,制备了改性MWNTs,将改性MWNTs作为一种新型的固相萃取吸附剂自制了固相萃取(SPE)柱,建立了以改性MWNTs作为SPE吸附剂测定农产品中痕量2甲4氯(MCPA)和2,4-滴(2,4-D)2种苯氧羧酸类除草剂的SPE/HPLC联用分析方法.考察了氧化处理、共价接枝、SPE柱操作和色谱条件等对实验结果的影响,并优化了实验条件.在优化实验条件下,2种除草剂在较宽质量浓度范围内线性关系良好,相关系数为0.9984～0.9995,检出限为0.020mg/L；对样品分别进行0.20、5.0、50 mg/L 3种水平的加标回收率实验,2种除草剂的加标回收率为81％～105％,RSD为3.2％～8.3％.该方法用于大豆、大米和茶叶等样品的净化,效果良好,测定结果准确、灵敏度高,符合农产品中低浓度农药残留的分析要求.

Determination of Phenoxyacid Herbicides in Agricultural Products by Solid Phase Extraction Using Modified Multi-walled Carbon Nanotubes as Adsorbent

An approach,including the surface acid oxidation and covalent grafting,was proposed to prepare modified multi-walled carbon nanotubes(MWNTs).Using multi-walled carbon nanotubes as a new type of solid phase extraction column,and a novel method was developed for the simultaneous determination of two phenoxyacid herbicides e.g.MCPA and 2,4-D in agricultural products by using multi-walled carbon nanotubes as solid phase extraction adsorbent coupled with high performance liquid chromatography(HPLC).The experimental conditions,including the surface acid oxidation,covalent grafting,SPE column operations and chromatography conditions,were optimized.Under the optimal conditions,the method provided a wide linear range for 2 phenoxyacid herbicides with correlation coefficients of 0.998 4-0.999 5,and the detection limit was 0.020 mg/L.The method was applied to detect the residues of phenoxyacid herbicides in soybean,rice and tea.The spiked recoveries for the samples at three spiked concentration levels of 0.20,5.0 and 50 mg/L were in the range of 81%-105 % with RSDs of 3.2%-8.3 %.The results indicated that using multi-walled carbon nanotubes as solid phase extraction adsorbent was efficient for the purification of the agricultural products(included soybean,rice and tea ).With the advantages of accuracy and sensitivity,the proposed method could meet the requirements for determination of low pesticide residues in agricultural products,and provide a useful approach for the analysis of trace substance of agricultural products.