Singh G, Gutierrez A, Xu K, Blair I A
Center for Cancer Pharmacology, University of Pennsylvania, Philadelphia 19104-6160, USA.
Anal Chem. 2000 Jul 15;72(14):3007-13. doi: 10.1021/ac000374a.
The corona discharge used to generate positive and negative ions under conventional atmospheric pressure chemical ionization conditions also provides a source of gas-phase electrons. This is thought to occur by displacement of electrons from the nitrogen sheath gas. Therefore, suitable analytes can undergo electron capture in the gas phase in a manner similar to that observed for gas chromatography/electron capture negative chemical ionization/mass spectrometry. This technique, which has been named electron capture atmospheric pressure chemical ionization/mass spectrometry, provided an increase in sensitivity of 2 orders of magnitude when compared with conventional atmospheric pressure chemical ionization methodology. It is a simple procedure to tag many biomolecules and drugs with an electron-capturing group such as the pentafluorobenzyl moiety before analysis. Pentafluorobenzyl derivatives have previously been used as electron capturing derivatives because they undergo dissociative electron capture in the gas phase to generate negative ions through the loss of a pentafluorobenzyl radical. A similar process was found to occur under electron capture atmospheric pressure chemical ionization conditions. By monitoring the negative ions that were formed, it was possible to obtain attomole sensitivity for pentafluorobenzyl derivatives of a representative steroid, steroid metabolite, prostaglandin, thromboxane, amino acid, and DNA-adduct.
在传统大气压化学电离条件下用于产生正离子和负离子的电晕放电也提供了气相电子源。据认为，这是通过氮鞘气中的电子位移而发生的。因此，合适的分析物可以在气相中进行电子捕获，其方式类似于在气相色谱/电子捕获负化学电离/质谱中观察到的方式。这种技术被命名为电子捕获大气压化学电离/质谱，与传统大气压化学电离方法相比，灵敏度提高了2个数量级。在分析之前，用电子捕获基团（如五氟苄基部分）标记许多生物分子和药物是一个简单的过程。五氟苄基衍生物以前被用作电子捕获衍生物，因为它们在气相中经历离解电子捕获，通过失去一个五氟苄基自由基而产生负离子。发现在电子捕获大气压化学电离条件下会发生类似的过程。通过监测形成的负离子，有可能获得代表性类固醇、类固醇代谢物、前列腺素、血栓烷、氨基酸和DNA加合物的五氟苄基衍生物的阿托摩尔灵敏度。
