Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511, Japan.
J Mass Spectrom. 2013 Mar;48(3):392-8. doi: 10.1002/jms.3173.
Super-atmospheric pressure chemical ionization (APCI) mass spectrometry was performed using a commercial mass spectrometer by pressurizing the ion source with compressed air up to 7 atm. Similar to typical APCI source, reactant ions in the experiment were generated with corona discharge using a needle electrode. Although a higher needle potential was necessary to initiate the corona discharge, discharge current and detected ion signal were stable at all tested pressures. A Roots booster pump with variable pumping speed was installed between the evacuation port of the mass spectrometer and the original rough pumps to maintain a same pressure in the first pumping stage of the mass spectrometer regardless of ion source pressure. Measurement of gaseous methamphetamine and research department explosive showed an increase in ion intensity with the ion source pressure until an optimum pressure at around 4-5 atm. Beyond 5 atm, the ion intensity decreased with further increase of pressure, likely due to greater ion losses inside the ion transport capillary. For benzene, it was found that besides molecular ion and protonated species, ion due to M + 2H which was not so common in APCI, was also observed with high ion abundance under super-atmospheric pressure condition.
采用商业质谱仪，通过将离子源加压至 7 个大气压的压缩空气，进行超大气压化学电离（APCI）质谱分析。与典型的 APCI 源类似，实验中使用针状电极的电晕放电产生反应离子。尽管需要更高的针状电势才能引发电晕放电，但在所有测试压力下，放电电流和检测到的离子信号都很稳定。在质谱仪的排气口和原始粗抽泵之间安装了一个 Roots 升压泵，该泵具有可变的泵送速度，可以在质谱仪的第一级泵送阶段保持相同的压力，而与离子源压力无关。对气态甲基苯丙胺和研究部门炸药的测量表明，随着离子源压力的增加，离子强度增加，直到约 4-5 个大气压的最佳压力。超过 5 个大气压后，随着压力的进一步增加，离子强度下降，这可能是由于在离子传输毛细管内更大的离子损失所致。对于苯，发现除了分子离子和质子化物质外，在超大气压条件下，由于M+2H而产生的离子也具有很高的离子丰度，这种离子在 APCI 中并不常见。
