Gas phase reactions between hydrated protons H+(H2O)n and a substance M, as seen in atmospheric pressure chemical ionization (APCI) with mass spectrometry (MS) and ion mobility spectrometry (IMS), were modeled computationally using initial amounts of [M] and [H+(H2O)n], rate constants k1 to form protonated monomer (MH+(H2O)x) and k2 to form proton bound dimer (M2H+(H2O)z), and diffusion constants. At 1 × 1010 cm-3 (0.4 ppb) for [H+(H2O)n] and vapor concentrations for M from 10 ppb to 10 ppm, a maximum signal was reached at 4.5 μs to 4.6 ms for MH+(H2O)x and 7.8 μs to 46 ms for M2H+(H2O)z. Maximum yield for protonated monomer for a reaction time of 1 ms was ∼40% for k1 from 10-11 to 10-8 cm3·s-1, for k2/k1 = 0.8, and specific values of [M]. This model demonstrates that ion distributions could be shifted from [M2H+(H2O)z] to [MH+(H2O)x] using excessive levels of [H+(H2O)n], even for [M] > 10 ppb, as commonly found in APCI MS and IMS measurements. Ion losses by collisions on surfaces were insignificant with losses of <0.5% for protonated monomer and <0.1% for proton bound dimer of dimethyl methylphosphonate (DMMP) at 5 ms. In this model, ion production in an APCI environment is treated over ranges of parameters important in mass spectrometric measurements. The models establish a foundation for detailed computations on response with mixtures of neutral substances.

中文翻译：

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大气压化学电离反应广义模型中的参数灵敏度。

水合质子 H+(H2O)n 和物质 M 之间的气相反应，如在大气压化学电离 (APCI) 与质谱 (MS) 和离子迁移谱 (IMS) 中所见，使用初始量 [M] 进行计算建模[H+(H2O)n]、形成质子化单体 (MH+(H2O)x) 的速率常数 k1 和形成质子结合二聚体 (M2H+(H2O)z) 的速率常数 k2，以及扩散常数。[H+(H2O)n] 为 1 × 1010 cm-3 (0.4 ppb)，M 的蒸气浓度为 10 ppb 至 10 ppm，MH+(H2O)x 和 7.8 的最大信号在 4.5 μs 至 4.6 ms 时达到M2H+(H2O)z 为 μs 至 46 ms。对于 10-11 到 10-8 cm3·s-1 的 k1，对于 k2/k1 = 0.8 和 [M] 的具体值，质子化单体的最大产率在 1 ms 的反应时间为 ~40%。该模型表明，即使 [M] > 10 ppb，也可以使用过量水平的 [H+(H2O)n] 将离子分布从 [M2H+(H2O)z] 转变为 [MH+(H2O)x]，如常见于APCI MS 和 IMS 测量。表面碰撞引起的离子损失微不足道，质子化单体的损失 <0.5%，甲基膦酸二甲酯 (DMMP) 的质子结合二聚体在 5 ms 时损失 <0.1%。在该模型中，APCI 环境中的离子产生在质谱测量中重要的参数范围内进行处理。这些模型为详细计算中性物质混合物的响应奠定了基础。5 ms 时甲基膦酸二甲酯 (DMMP) 的质子结合二聚体为 1%。在该模型中，APCI 环境中的离子产生在质谱测量中重要的参数范围内进行处理。这些模型为详细计算中性物质混合物的响应奠定了基础。5 ms 时甲基膦酸二甲酯 (DMMP) 的质子结合二聚体为 1%。在该模型中，APCI 环境中的离子产生在质谱测量中重要的参数范围内进行处理。这些模型为详细计算中性物质混合物的响应奠定了基础。