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发布者:鑫达医学翻译公司 发布时间:2011-07-12阅读:

原文:
To maximize sensitivity for the analytes in MS/MS operation, various parameters affecting collision induced dissociation efficiency (CID) were optimized, including the choice of the precursor and product ions, excitation amplitude (EA), and the stability parameter (qz). BeforeMS/MSmethod development, the chromatographic segments for the target compounds were established based on their retention times in full scan mode. Then, from the full scan GC/MSspectra, the most abundant ion or fragment ion with a higher m/z and higher intensity of each compound was selected as the precursor ion, and subjected to further CID in a non-resonant excitation mode for MS/MS analysis. The automated method development (AMD) tool in the software was used to optimize EA. With a qz of 0.4, the EA was calculated using three injections of a standard solution of a mixture of analytes at 100 g/L. In the first injection, EA increased from 10 to 100V at an interval of 10 V, and then EA varied within narrow ranges for each compound with intervals of 5 and 3V in the second and third injections, respectively. The qz was related to the broadband multi-frequency waveform used to isolate the precursor ion, and was expressed as an excitation storage level (ESL) in the software. Under the optimal EA for the precursor ions, a set of qz values from 0.2 to 0.5 was tested to obtain the greatest intensity for the product ions. In addition, the mass defect (−50, 0 and +50mm /100 ), multiplier offset (100, 200 and 250 V), and mass range of the scanned ions were evaluated to maximize the pyrethroid signals as well.

译文:
为使MS/MS操作对分析物的灵敏度达最高值,对影响碰撞诱导接离(CID)效率的不同参数进行优化,包括所选前体离子和产物离子、激发振幅(EA)与稳定性参数(qz)等。研发MS/MS前,根据目标化合物的全扫描模式下的滞留时间确立色谱段。然后,自全扫描GC/MS谱下选择每种化合物丰度最高的离子或碎片离子(质核比[m/z]与强度较高)作为前体离子,在非共振激发模式(用于MS/MS分析)下进行进一步CID。软件内的自动方法研发(AMD)工具用以优化EA。qz为0.4时,三次注射分析物混合(100μg/L)标准溶液以校准EA。首次注射时,EA自10V增加至100V(增幅为10V)。第二次注射与第三次注射每种化合物增幅范围变小,分别为5V与3V。qz与用以分离前体离子的宽带与多频率波形相关,在软件内以激发储能能级的形式表示。在前体离子的最佳EA下,测试一组qz值(0.2~0.5)以获取产物离子的最高强度。此外,对质量亏损(−50、0、+50mmμ/100μ)、倍增偏移电压(100、200与250 V)与扫描离子的质量范围进行评价,以实现拟除虫菊酯信号的最大化。
 


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