Adsorption of acetanilide herbicides on soil and its components Ⅱ. Adsorption and catalytic hydrolysis of diethatyl-ethyl on saturated Na^+-, K^+-, Ca^(2+)-, and Mg^(2+)- montmorillonite

Adsorption and catalytic hydrolysis of the herbicide diethatyl ethyl [N chloroacetyl N (2,6 diethylphenyl)glycine ethyl ester] on homoionic Na + , K + , Ca 2+ , and Mg 2+ montmorillonite clays were investigated in water solution. The Freundlich adsorption coefficient, K f, got from isotherms on clay followed the order of Na +≈K +>Mg 2+ ≈Ca 2+ . Analysis of FT IR spectra of diethatyl ethyl adsorbed on clay suggests probable bonding at the carboxyl and amide carbonyl groups of the herbicide. The rate of herbicide hydrolysis in homoionic clay suspensions followed the same order as that for adsorption, indicating that adsorption may have preceded and thus caused hydrolysis. Preliminary product identification showed that hydrolysis occurred via nucleophilic substitution at the carboxyl carbon, causing the cleavage of the ester bond and formation of diethatyl and its dechlorinated derivative, and at the amide carbon, yielding an ethyl ester derivative and its acid. These pathways also suggest that hydrolysis of diethatyl ethyl was catalyzed by adsorption on the clay surface.

液相色谱-质谱联用检测蒲公英茶中的乙酰甲草胺

目的:为了更有效地对我国蒲公英茶的质量和安全性进行监管,建立液相色谱-质谱联用检测蒲公英茶中的乙酰甲草胺的方法。方法:干燥后的蒲公英茶试样用含0.1%甲酸的乙腈溶液提取、脱色净化,离心,过0.22μm微孔滤膜,用液相色谱质谱法检测。采用C18(150 mm×4.6 mm,5μm)液相色谱柱分离,采用ESI+、MRM模式检测。结果:乙酰甲草胺浓度在0.1~100.0μg·L^(-1),曲线方程为y=2950x+89785,相关系数r=0.997,线性关系良好;在0.5μg·kg^(-1)、10.0μg·kg^(-1)、50.0μg·kg^(-1)3个添加水平下,乙酰甲草胺的平均回收率在99.06%,相对标准偏差为9.6%。结论:使用液相色谱-质谱联用检测蒲公英茶中的乙酰甲草胺的方法快捷,准确度、精密度好,可以满足蒲公英茶中乙酰甲草胺残留的定性和定量检测。

QuEChERS-液相色谱-串联质谱法测定植物源食品中氟噻草胺和乙酰甲草胺残留

建立了QuEChERS前处理-液相色谱-串联质谱仪(HPLC-MS/MS)测定植物源食品中氟噻草胺和乙酰甲草胺残留量的分析方法。样品经酸化乙腈(含0.1%甲酸的乙腈)提取,采用石墨化碳黑(GCB)净化,提取液经离心、过膜后直接上机检测。该方法采用C18色谱柱进行色谱分离,以0.1%甲酸水(含5mmol/mL乙酸铵)-甲醇为流动相,在0.25mL/min流速下梯度洗脱,电喷雾正离子电离(ESI+),多重反应监测模式(MRM)检测,以保留时间和特征离子对(母离子和两个碎片离子)信息比较进行定性,基质匹配曲线定量。在9种基质(葡萄、葡萄干、黄瓜、小麦粉、苹果、白菜、枸杞、西红柿和大米)中,氟噻草胺和乙酰甲草胺在0.25~25.0μg/L范围内线性关系良好,相关系数均大于0.997,两种化合物的方法定量限为0.5μg/kg;在0.5,1.0,5.0μg/kg3个添加水平下,氟噻草胺的平均回收率在82.5%~103.9%,相对标准偏差为2.9%~15%;乙酰甲草胺的回收率在81.7%~108.1%,相对标准偏差在3.1%~14%。方法灵敏度、准确度和精密度均符合农药残留检测要求。