目的：磺酰脲类和磺酰胺类除草剂属内吸传导性药剂，此类除草剂具有用量少、高效、广谱、低毒和高选择性等特点，在农业生产中被广泛使用。其中，苯磺隆、苄嘧磺隆、氯磺隆、双氟磺草胺被用于防除阔叶杂草。使用此类制剂时，若剂量不当，容易对当茬及后茬轮种作物造成一定的药害。正是由于某些作物对此类除草剂的敏感性，犯罪分子实施不法行为的相关案件频繁发生。鉴于此，本文以苯磺隆、苄嘧磺隆、氯磺隆和双氟磺草胺为代表，对土壤中此类除草剂的提取、检验方法以及鉴定时效性进行系统研究。方法分别利用常见溶剂甲醇、乙腈、丙酮和水对土壤中此类除草剂进行提取，计算提取率。并通过对同一溶剂提取物的重复测定，考查目标物在不同提取溶剂中的分解速度。兼顾分析物的提取率和稳定性，确定最佳提取试剂。液相色谱和质谱的基本条件如下：色谱柱：Agilent Eclipse XDB-C18（4.6mm×150mm，5μm）。色谱条件：进样量10μL ；流动相 A 为甲醇，流动相 B 为0.1%甲酸（V/V）的水溶液。质谱条件：离子源：ESI ；CUR ：20 psi ；GS1：65 psi； GS2：55 psi，气体均为 N2；加热头温度650℃。喷雾电压 IS ：5500 V(+)/4500(-)。MRM 模式选取离子对：苯磺隆：396.2/199.0、396.2/181.2、396.2/154.9、396.2/135.2；苄嘧磺隆：411.2/182.1、411.2/149.0、411.2/139.1、411.2/119.1；氯磺隆：355.9/139.1、355.9/124.3、355.9/107.2、355.9/82.2；双氟磺草胺：358.1/167.2、358.1/152.0、358.1/131.9、358.1/104.2。通过优化液相洗脱模式、流动相组成、不同化合物的去簇电压(DP)和不同特征碎片离子的碰撞能(CE)，确定目标物的最佳定性、定量分析方法。在此基础上，通过向空白土壤中添加一定浓度的标准物质，以24 h 为间隔依次进行提取分析，并通过峰面积定量（定量离子对：苯磺隆396.2/154.9；苄嘧磺隆411.2/149.0；氯磺隆355.9/139.1；双氟磺草胺358.1/167.2），初步考查此类除草剂在土壤中的降解趋势。结果甲醇、乙腈、丙酮、水四种常见溶剂对土壤中此类除草剂的提取率差异很大。甲醇对所有目标物提取效果均比较好，乙腈的提取效果与之相近，优于丙酮，且显著优于水。不同分析物在提取溶剂中的稳定性明显不同：15 h 内，氯磺隆、双氟磺草胺在四种溶剂中均未出现显著分解，苯磺隆、苄嘧磺隆在甲醇、乙腈、丙酮中的分解速率大约为7.0%/h，而在水中高达10%/h。兼顾目标物的提取率及其在不同溶剂中的稳定性，甲醇成为最优提取溶剂，对四种分析物的平均提取率均可达到67%以上。液相色谱洗脱梯度的设置和溶剂强度的选择对分析物的保留时间、分离度及峰形均有较大影响。当使用甲醇和0.1%甲酸水溶液进行等度洗脱（各50%）时，双氟磺草胺峰形较差，且由于溶剂强度较弱，苯磺隆、苄嘧磺隆、氯磺隆均无法被有效洗脱。采用梯度洗脱模式并保持相关参数，用乙腈代替甲醇作为有机相时，目标物的保留和峰形均较好，但分离选择性变差。最终，采用梯度洗脱模式，并利用甲醇和0.1%甲酸水溶液作为流动相。当流动相的流速在400~600μL/min 之间变化时，随流速变大，目标物保留时间缩短，但峰强度显著降低。为保证检测灵敏度，设置流速为400μL/min。通过优化电离模式、DP、CE 等质谱条件，苯磺隆和苄嘧磺隆在正离子模式下或氯磺隆和双氟磺草胺在负离子模式下均可得到良好的检测。通过此类除草剂的稳定性考查实验发现，经过30天，土壤中分析物含量衰减至初始含量的20%~40%。为确保鉴定的有效性，此类案件相关的检材提取、送检以及检验均应及时、迅速。通过系列土样测定，得到苯磺隆、苄嘧磺隆和氯磺隆、双氟磺草胺的工作曲线线性范围分别为0.25~5μg/g 和0.05~5μg/g，相关系数均大于0.99，方法检出阈为1.0~20 ng/g。结论利用固液萃取和液相色谱-串联质谱法，建立了土壤中磺酰脲类和磺酰胺类除草剂的提取及鉴定方法。该方法提取过程简单，检测灵敏度高，可用于实际案件中此类除草剂的检验。鉴于此类药剂对防除对象的作用机制及其自身性质，时效性在案件侦办中极为重要，办案及鉴定人员应着重注意。%Objective To establish a method for extraction and detection of sulfonylurea and sulfamide herbicides in soil using tribenuron methyl, bensulfuron methyl, chlorsulfuron and florasulam as test samples. Methods Solid-liquid extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed for analysis of the target samples. In order to reduce sample loss in the procedure of solid-liquid extraction, the polarity-different solvents of methanol, acetonitrile, acetone and water were tested to determine the recovery of each analyte. The optimized conditions were chosen on consideration of both the extraction ratio and sample stability. Characterized ion pairs (396.2/199.0, 396.2/181.2, 396.2/154.9, 396.2/135.2 for tribenuron methyl, 411.2/182.1, 411.2/149.0, 411.2/139.1, 411.2/119.1 for bensulfuron methyl, 355.9/139.1, 355.9/124.3, 355.9/107.2, 355.9/82.2 for chlorsulfuron, and 358.1/167.2, 358.1/152.0, 358.1/131.9, 358.1/104.2 for florasulam) acquired from tandem mass spectrometry were taken for qualitative and quantitative analysis of the herbicides. On basis of the previous researches, degradation tendency of the analytes spiked into soil was determined by day to day experiment. Results The average recovery, determined by a known amount of herbicide standards spiked into soil samples, was above 67% with limits of detection ranging from 1.0 to 20 ng/g and decomposition velocity lower than 7.3%/h when methanol was taken as the extraction solvent. The working curves were constructed between peak area and concentration with all of the correlation coefficients greater than 0.99. Linear ranges were 0.25~5.0 μg/g for tribenuron methyl and bensulfuron methyl, and 0.05~5.0μg/g for chlorsulfuron and florasulam. In 30 days, tribenuron methyl, bensulfuron methyl, chlorsulfuron and florasulam standards, spiked into soil samples, degraded to 20%, 20%, 40% and 30% of their original amounts, respectively. Conclusions The proposed method is facilitating, fast, sensitive and applicable to the qualitative and quantitative analysis of sulfonylurea and sulfamide herbicides left in soil. The strategy can be readily implemented in criminal cases relating with crop damage. According to the results of decomposition tendency, a special attention should be paid that such analytes are quite sensitive to environment. For actual application, sample preparation and determination should be performed in short time so as to avoid false negative response caused by degradation.
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