【摘要】 根据表面解吸常压化学电离源(SDAPCI)对表面痕量待测物进行常压解吸化学电离的原理,自行研制了SDAPCI电离源及其与线性离子阱(LTQ)质谱仪的接口,成功地在LTQ上实现了表面解吸常压化学电离。此方法无需样品预处理,直接利用电晕放电产生的H3O+在常压下对待测样品进行表面解吸化学电离,避免了甲醇等有毒试剂的使用。在优化的仪器参数条件下,分别用正/负离子模式成功地检测了片剂药品中的氯雷他定、乙酰氨基酚等活性成分和其它不同表面上TNT、氨基酸和多肽等物质,对这些常见物质的检出限不高于10pg/cm2。采用氩气作为电离试剂,观测到乙酰氨基酚、多肽等物质形成的自由基阳离子,提出了在氩气氛围中获得自由基阳离子的可能机理。实验表明SDAPCI具有灵敏度较高,选择性好,适用范围宽等特点,适合用于药品、食品等非破坏、无污染检测以及对复杂基体物质进行快速现场分析。更多还原

【Abstract】 Combining the advantages of desorption electrospray ionization(DESI) and atmospheric pressure chemical ionization(APCI),a novel ambient surface desorption atmospheric pressure chemical ionization(SDAPCI) source was developed for direct detection of trace amounts of analytes in various complex matrices without any sample pretreatment.In the SDAPCI source,a self-assembled corona discharge was employed to generate the primary ions such as H3O+ in positive ion detection mode and H2O·OH-in negative ion detection mode,which were directed to impact the sample surface to yield positive/negative ions of interest for mass analysis.Using ambient air about 45%-60% relative water moisture as a reagent for chemical ionization,SDAPCI allows mass spectrometric analysis of ambient samples without toxic contamination and provides simplicity for in-situ analysis in a miniature mass spectrometer.The principle and construction of the SDAPCI source are presented in this contribution.A commercially available Claritin tablet,which was used to characterize a DESI source previously,was used to characterize the SDAPCI source.Under the optimal experimental conditions,loratadine(MW 382),an active ingredient of Claritin tablet,yields a high signal as protonated molecule(m/z 383),which loses ethanol to give a major fragment(m/z 337) upon collision-induced dissociation.Compared to DESI,a higher intensity was achieved in SDAPCI at 4 kV with ambient air as reagent gas for the Claritin tablet.Using pure argon gas instead of the ambient air,radical cations of acetaminophenol and peptide I-7 were successfully observed and structurally characterized by MS/MS experiments,which provided the first experimental evidence for production of radical cation of peptides at atmospheric pressure ambient.An electron stripping process caused by argon cation was thereby proposed to be the mechanism of radical cation formation in the SDAPCI source.The data show promising applications for direct analysis of ambient surfaces without sample contamination by toxic chemicals.更多还原