Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition bypro...Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition byproduct hydroxyatrazine on different soils, including measurements made using LC-MS/MS. These studies have now been extended to explore sorption-desorption equilibria for a mixture of pesticides from soil using LC-MS/MS. Desorption of sorbed pesticide residues has environmental regulatory implications for pesticide levels in runoff, or for longer term sequestration, partitioning, and transport. The uptake of pesticides by the soil at equilibrium was measured for a number of different concentrations, and sorption capacities were estimated. Pesticide-soil interaction studies were conducted by exposing standard stock solutions of pesticide mixtures to a characterized Nova Scotia soil. The mixture contained atrazine and dicamba. Initial aqueous mixture concentrations ranging from 5 × 10<sup>-9</sup> to 10<sup>-5</sup> M or greater were exposed to 25 mg aliquots of soil and allowed to reach equilibrium. The total uptake of each pesticide was measured indirectly, by measuring the concentration remaining in solution using an IONICS 3Q 120 triple quadrupole mass spectrometer. These sorption capacities have been supplemented by studies examining equilibrium recovery rates from soil aliquots with different initial uptakes. This gives insight into the fraction of easily recoverable (reversibly sorbed) pesticides on the soil. Proper quantification of equilibrium constants and kinetic rate coefficients using high performance LC-MS/MS facilitates the construction of accurate, predictive models. Predictive kinetic models can successfully mimic the experimental results for solution concentration, labile sorption, and intra-particle diffusion, and could be used to guide regulatory practices.展开更多
多路同步的高电压脉冲有广泛应用前景。为此,对基于可饱和脉冲变压器的多路同步技术路线进行了详细阐述,并开展了实验验证。在此基础之上,提出了多次级可饱和脉冲变压器多路同步控制的新型LC发生器。在该发生器中,可饱和脉冲变压器先后...多路同步的高电压脉冲有广泛应用前景。为此,对基于可饱和脉冲变压器的多路同步技术路线进行了详细阐述,并开展了实验验证。在此基础之上,提出了多次级可饱和脉冲变压器多路同步控制的新型LC发生器。在该发生器中,可饱和脉冲变压器先后承4重功能,极大地减小了系统的复杂程度。实验中,初级输入电压为910V时,输出电压幅值达到110 k V,系统总的升压倍数达121倍。此外,引入半导体断路开关,可使实验中输出脉冲的上升沿在20 ns以内。同时将半导体断路开关与电感储能型脉冲形成线相结合,提出了低阻抗方波脉冲的产生方案。研究结果表明:提出的技术方案确实可行,对脉冲功率技术向固态化、小型紧凑化以及可重复频率运行方向发展具有较大的探索意义。展开更多
针对经典轨迹相似度量的耗时性,利用轨迹压缩算法,提出一种基于最长公共子序列(longest common subsequence,LCS)的相似度量快速算法。首先,对实时轨迹进行压缩,减少轨迹点数。然后,利用经典轨迹的点与实时轨迹线段之间的距离,根据改进...针对经典轨迹相似度量的耗时性,利用轨迹压缩算法,提出一种基于最长公共子序列(longest common subsequence,LCS)的相似度量快速算法。首先,对实时轨迹进行压缩,减少轨迹点数。然后,利用经典轨迹的点与实时轨迹线段之间的距离,根据改进的多对1 LCS长度公式,计算经典轨迹与实时轨迹之间的LCS长度。最后,将LCS长度与经典轨迹的点数的比值作为经典轨迹的相似度。实验说明,通过轨迹压缩能够减少60%以上的计算时间。展开更多
建立快速测定猪肉中克伦特罗残留量的液相色谱串联质谱分析方法。猪肉样品在碱化的条件下用乙酸乙酯提取,提取后用甲酸溶液进行反萃取,萃取液经正已烷脱脂后直接进行液相色谱串联质谱(liquid chromatography with tandem mass spectrome...建立快速测定猪肉中克伦特罗残留量的液相色谱串联质谱分析方法。猪肉样品在碱化的条件下用乙酸乙酯提取,提取后用甲酸溶液进行反萃取,萃取液经正已烷脱脂后直接进行液相色谱串联质谱(liquid chromatography with tandem mass spectrometry,LC-MS/MS)分析。采用Acquity BEH C_(18)色谱柱分离,用0.1%甲酸溶液-甲醇作为流动相进行梯度洗脱,电喷雾正离子(ESI^+)模式电离,多反应监测(multiple reaction monitoring,MRM)模式检测,同位素稀释内标法定量。克伦特罗在0.05~10.0μg/L范围内建立的曲线相关系数大于0.999;方法检测限为0.10μg/kg,定量限为0.25μg/kg。克伦特罗在猪肉中的添加量为0.25、0.50、0.75μg/kg时,平均回收率在95.9%~101.5%之间,批内相对标准偏差(relative standard deviation,RSD)在3.3%~4.6%之间,批间RSD在4.1%~5.1%之间。该方法能满足猪肉中克伦特罗残留量快速分析的要求。展开更多
文摘Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition byproduct hydroxyatrazine on different soils, including measurements made using LC-MS/MS. These studies have now been extended to explore sorption-desorption equilibria for a mixture of pesticides from soil using LC-MS/MS. Desorption of sorbed pesticide residues has environmental regulatory implications for pesticide levels in runoff, or for longer term sequestration, partitioning, and transport. The uptake of pesticides by the soil at equilibrium was measured for a number of different concentrations, and sorption capacities were estimated. Pesticide-soil interaction studies were conducted by exposing standard stock solutions of pesticide mixtures to a characterized Nova Scotia soil. The mixture contained atrazine and dicamba. Initial aqueous mixture concentrations ranging from 5 × 10<sup>-9</sup> to 10<sup>-5</sup> M or greater were exposed to 25 mg aliquots of soil and allowed to reach equilibrium. The total uptake of each pesticide was measured indirectly, by measuring the concentration remaining in solution using an IONICS 3Q 120 triple quadrupole mass spectrometer. These sorption capacities have been supplemented by studies examining equilibrium recovery rates from soil aliquots with different initial uptakes. This gives insight into the fraction of easily recoverable (reversibly sorbed) pesticides on the soil. Proper quantification of equilibrium constants and kinetic rate coefficients using high performance LC-MS/MS facilitates the construction of accurate, predictive models. Predictive kinetic models can successfully mimic the experimental results for solution concentration, labile sorption, and intra-particle diffusion, and could be used to guide regulatory practices.
文摘多路同步的高电压脉冲有广泛应用前景。为此,对基于可饱和脉冲变压器的多路同步技术路线进行了详细阐述,并开展了实验验证。在此基础之上,提出了多次级可饱和脉冲变压器多路同步控制的新型LC发生器。在该发生器中,可饱和脉冲变压器先后承4重功能,极大地减小了系统的复杂程度。实验中,初级输入电压为910V时,输出电压幅值达到110 k V,系统总的升压倍数达121倍。此外,引入半导体断路开关,可使实验中输出脉冲的上升沿在20 ns以内。同时将半导体断路开关与电感储能型脉冲形成线相结合,提出了低阻抗方波脉冲的产生方案。研究结果表明:提出的技术方案确实可行,对脉冲功率技术向固态化、小型紧凑化以及可重复频率运行方向发展具有较大的探索意义。
文摘针对经典轨迹相似度量的耗时性,利用轨迹压缩算法,提出一种基于最长公共子序列(longest common subsequence,LCS)的相似度量快速算法。首先,对实时轨迹进行压缩,减少轨迹点数。然后,利用经典轨迹的点与实时轨迹线段之间的距离,根据改进的多对1 LCS长度公式,计算经典轨迹与实时轨迹之间的LCS长度。最后,将LCS长度与经典轨迹的点数的比值作为经典轨迹的相似度。实验说明,通过轨迹压缩能够减少60%以上的计算时间。
文摘建立快速测定猪肉中克伦特罗残留量的液相色谱串联质谱分析方法。猪肉样品在碱化的条件下用乙酸乙酯提取,提取后用甲酸溶液进行反萃取,萃取液经正已烷脱脂后直接进行液相色谱串联质谱(liquid chromatography with tandem mass spectrometry,LC-MS/MS)分析。采用Acquity BEH C_(18)色谱柱分离,用0.1%甲酸溶液-甲醇作为流动相进行梯度洗脱,电喷雾正离子(ESI^+)模式电离,多反应监测(multiple reaction monitoring,MRM)模式检测,同位素稀释内标法定量。克伦特罗在0.05~10.0μg/L范围内建立的曲线相关系数大于0.999;方法检测限为0.10μg/kg,定量限为0.25μg/kg。克伦特罗在猪肉中的添加量为0.25、0.50、0.75μg/kg时,平均回收率在95.9%~101.5%之间,批内相对标准偏差(relative standard deviation,RSD)在3.3%~4.6%之间,批间RSD在4.1%~5.1%之间。该方法能满足猪肉中克伦特罗残留量快速分析的要求。
