Capillary Electrochromatography Coupled to Atmospheric Pressure Photoionization Mass Spectrometry for Methylated Benzo[a]pyrene Isomers

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• 作者：Jie Zheng ; Shahab A. Shamsi
• 刊名：Analytical Chemistry
• 出版年：2006
• 出版时间：October 1, 2006
• 年：2006
• 卷：78
• 期：19
• 页码：6921 - 6927
• 全文大小：309K
• 年卷期：v.78,no.19(October 1, 2006)
• ISSN：1520-6882

文摘

Benzo[a]pyrene, one of the most carcinogenic PAHs, has12 monomethylated positional isomers (MBAPs). A strongcorrelation between the carcinogenicity of these isomersand methyl substitution has been reported. In this study,on-line coupling of capillary electrochromatography (CEC)and atmospheric pressure photoionization mass spectrometry (APPI-MS) provides a unique solution to highlyselective separation and sensitive detection of MBAPisomers. The studies indicated that APPI provides significantly better sensitivity compared to electrosprayionization and atmospheric pressure chemical ionizationmodes of MS. A systematic investigation of APPI-MSdetection parameters and CEC separation is established.First, several sheath liquid parameters (including type andconcentration of volatile buffers, type and content oforganic modifiers, use of dopants and inorganic/organicadditives, and sheath liquid flow rate) and APPI-MS spraychamber parameters (capillary voltage, vaporizer temperature, nebulizer pressure) were found to have effects ondetection sensitivity as well as the profile of mass spectrum. For example, when ammonium acetate was replaced with acetic acid in the sheath liquid, the MS signalwas enhanced as much as 90% and the formation ofammonia adduct was effectively suppressed. Next, theseparation of MBAP isomers was conducted on internaltapered columns packed with polymeric C₁₈ stationaryphase. With the use of a mobile phase consisting of slightlyhigher acetonitrile content (90%,v/v) and a small amountof tropylium ion, the analysis times were significantlyshortened by 20 min without compromising the resolutions between the isomers. Finally, quantitative aspectsof the CEC-APPI-MS method were demonstrated using7-MBAP as the internal standard. The calibration curvesof three of the most carcinogenic isomers, namely, 1-MBAP, 3-MBAP, and 11-MBAP, showed good linearity inthe range of 2.5-50 g/mL with a limit of detection at400 ng/mL.