Atmospheric pressure chemical ionizations (APCIs) of morphine, codeine, and thebaine were studied in a corona discharge ion source using ion mobility spectrometry (IMS) at temperature range of 100°C–200°C. Density functional theory (DFT) at the B3LYP/6‐311++G(d,p) and M062X/6‐311++G(d,p) levels of theory were used to interpret the experimental data. It was found that in the presence of H₃O⁺ as reactant ion (RI), ionization of morphine and codeine proceeds via both the protonation and carbocation formation, whereas thebaine participates only in protonation. Carbocation formation (fragmentation) was diminished with decrease in the temperature. At lower temperatures, proton‐bound dimers of the compounds were also formed. Ammonia was used as a dopant to produce NH₄⁺ as an alternative RI. In the presence of NH₄⁺, proton transfer from ammonium ion to morphine, codeine, and thebaine was the dominant mechanism of ionization. However, small amount of ammonium attachment was also observed. The theoretical calculations showed that nitrogen atom of the molecules is the most favorable proton acceptor site while the oxygen atoms participate in ammonium attachment. Furthermore, formation of the carbocations is because of the water elimination from the protonated forms of morphine and codeine.

中文翻译：

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电晕放电离子迁移谱法中吗啡，可待因和蒂巴因的常压化学电离机理：质子化，铵离子附着和碳阳离子形成。

在电晕放电离子源中使用离子迁移谱（IMS）在100°C–200°C的温度范围内研究了吗啡，可待因和蒂巴因的大气压化学电离（APCI）。使用B3LYP / 6-311 ++ G（d，p）和M062X / 6-311 ++ G（d，p）的密度泛函理论（DFT）来解释实验数据。发现在存在H ₃ O ⁺作为反应物离子（RI）的情况下，吗啡和可待因的电离通过质子化和碳正离子化两者进行，而蒂巴因仅参与质子化。随着温度降低，碳正离子形成（碎片化）减少。在较低温度下，还会形成化合物的质子结合二聚体。氨被用作生产NH ₄的掺杂剂⁺作为替代RI。在NH ₄ ⁺存在下，质子从铵离子转移到吗啡，可待因和蒂巴因是电离的主要机理。但是，也观察到少量的铵附着。理论计算表明，分子中的氮原子是最有利的质子受体位点，而氧原子则参与铵的附着。此外，形成碳阳离子的原因是由于从吗啡和可待因的质子化形式中除去了水。