In this study, gas chromatography-tandem mass spectrometry (GC-MS/MS) using an atmospheric pressure chemical ionization (APCI) source was applied for the quantitative analysis of pesticide residues in tea. To determine the optimum ionization conditions for multiresidue analysis, the full-scan mass spectra and peak intensities of pesticides were compared in the presence and absence of water as a modifier. When water was added as a modifier in the ion source, most of the target compounds formed [M+H]+ ions and exhibited enhanced intensities. However, compounds consisting of only carbon, hydrogen, and chlorine, such as aldrin, γ-hexachlorocyclohexane, and p,p'-dichlorodiphenyldichloroethane, typically formed M+· or fragment ions, whose intensities were significantly decreased by the addition of water. GC-MS/MS methods using APCI (without modifier addition) and electron ionization (EI) were validated for 16 pesticides in tea at spiking levels of 0.01 and 0.1 mg/kg. Unlike EI, signal suppression was observed for most compounds at a spiking level of 0.01 mg/kg using APCI; however, dilution of the samples minimized this effect. Using APCI, the trueness of the target compounds ranged from 77% to 121% at both spiking levels, except for pyrethrins owing to matrix effects, with relative standard deviations of less than 14%. For most compounds, these results were comparable with those obtained using EI. However, because the use of APCI limited fragmentation, this ionization technique offered significantly higher sensitivity and specificity than EI. Using APCI, linear calibration curves with coefficients of determination greater than 0.998 were obtained in the range of 0.0005-0.5 μg/mL for all compounds. These findings indicated that GC-MS/MS with APCI is applicable for the routine monitoring of pesticide residues, even in complex samples such as tea.

中文翻译：

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气相色谱-串联质谱联用大气压化学电离对茶叶中的农药残留进行定量分析。

在这项研究中，采用大气压化学电离（APCI）源的气相色谱-串联质谱（GC-MS / MS）用于茶叶中农药残留的定量分析。为了确定用于多残留分析的最佳电离条件，比较了在有水和无水作为改性剂的情况下农药的全扫描质谱图和峰强度。当在离子源中添加水作为改性剂时，大多数目标化合物会形成[M + H] +离子并显示出增强的强度。但是，仅由碳，氢和氯组成的化合物（如艾氏剂，γ-六氯环己烷和p，p'-二氯二苯基二氯乙烷）通常会形成M +·或碎片离子，通过添加水其强度会大大降低。使用APCI（不添加改性剂）和电子电离（EI）的GC-MS / MS方法已针对茶叶中16种农药的加标水平分别为0.01和0.1 mg / kg进行了验证。与EI不同，使用APCI可以观察到大多数化合物的信号抑制为0.01 mg / kg的峰值。但是，样品稀释会使这种影响最小化。使用APCI，除了由于基质效应引起的除虫菊酯外，两种加标水平下目标化合物的真实度在77％至121％范围内，相对标准偏差小于14％。对于大多数化合物，这些结果与使用EI获得的结果相当。但是，由于使用APCI限制了片段化，因此该电离技术提供的灵敏度和特异性比EI高得多。使用APCI，线性校正曲线的测定系数大于0。对于所有化合物，在0.0005-0.5μg/ mL范围内获得998。这些发现表明，带有APCI的GC-MS / MS适用于农药残留的常规监测，即使在茶叶等复杂样品中也是如此。