气相色谱-氮磷检测器测定草甘膦在土壤和苹果中的残留量

建立了简单、灵敏的土壤及苹果中草甘膦残留量的气相色谱检测方法。土壤样品用2 mol/L 的氨水提取,经三氟乙酸酐(TFAA)和三氟乙醇(TFE)衍生化后,由配有氮磷检测器的气 相色谱(GC-NPD)进行检测。土壤中草甘膦的最小检出量为9×10-12 g,最低检出浓度为0.02 mg/kg, 平均回收率及变异系数分别为84.4% ~94.0% 和7.46% ~10.40%。苹果样品则采用去离子水提取,经二氯甲烷液液分配和BIO-RAD AG 50W-X8阳离子交换柱净化后,再用TEAA和TFE衍生化,最后用GC-NPD检测,其中草甘膦的最小检出量(LOD)和最低检出浓度(LOQ)与土壤样品中的相同,平均回收率及变异系数分别为80.7% ~98.6%和9.3% ~11.8%。草甘膦的衍生化产物通过气相色谱-质谱联用仪(GC-MS)进行了确证。在北京昌平地区进行的消解动态和最终残留试验结果表明,以推荐高剂量(有效浓度)的1.5倍(2 025 g/hm2)施药,草甘膦在土壤中的半衰期为 9.2 d。两年的最终残留试验结果表明,无论是高浓度区(2 025 g/hm2)还是低浓度区(1 350 g/hm2),苹果收获时(距施药75 d),土壤和苹果样品中均未检出草甘膦。

Determination of Glyphosate Residues in Soil and Apple by Capillary Gas Chromatography with Nitrogen-Phosphorus Detection

A simple,sensitive and selective method using gas chromatorgaphy(GC)was developed to determine residues of glyphosate in soil and apple.The soil sample was extracted with 2 mol/L NH₄OH,treated with trifluoroacetic anhydride(TFAA) and trifluoroethanol(TFE),and then determined by gas chromatorgaphy(GC)with nitrogen-phosphorus detector (NPD).The limit of detection was estimated to be 9×10^-12 g,and the minimum determination concentration of glyphosate in soil samples was 0.02 mg/kg.The ranges of average recoveries and coefficient variation of the method were 84.4%~94.0% and 7.46%~10.40%,respectively.Apple samples were extracted with deionized water and cleaned by extraction with dichloromethane and solid phase extraction with BIO- RAD AG 50W-X8 cation exchange columns,then TFAA and TFE,and detected by GC-NPD.The limit of detection and the minimum determination concentration of glyphosate in apple were the same as the soil samples,but the ranges of average recoveries and coefficient variation of the method were 80.7% ~98.6% and 9.3% ~11.8%,respectively.The structure of derivative compound was confirmed by gas chromatography-mass spectrometry(GC-MS).Dissipation study showed that the half-life obtained for glyphosate in soil was approximately 9.2 days at 1.5 times of the recommended dosage in an apple orchard.No glyphosate residues was detected in apple and soil samples at treatments of 1 350 ~2 025 g(a.i.)/hm² at harvest season (75 days after the treatment).