Capillary Electrochromatography-Mass Spectrometry of Zwitterionic Surfactants
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- 作者：Dean Norton ; Jack Zheng ; Neil D. Danielson ; and Shahab A. Shamsi
- 刊名：Analytical Chemistry
- 出版年：2005
- 出版时间：November 1, 2005
- 年：2005
- 卷：77
- 期：21
- 页码：6874 - 6886
- 全文大小：1069K
- 年卷期：v.77,no.21(November 1, 2005)
- ISSN：1520-6882
文摘
This work describes the on-line hyphenation of a packedcapillary electrochromatography (CEC) column with aninternally tapered tip coupled to electrospray ionization-mass spectrometry (ESI-MS) and atmospheric pressurechemical ionization-mass spectrometry (APCI-MS) for theanalysis of betaine-type amphoteric or zwitterionic surfactants (Zwittergent). A systematic investigation of theCEC separation and MS detection parameters comparingESI and APCI is shown. First, a detailed and optimizedmanufacturing procedure for fabrication of the CEC-MScolumn with a reproducible internally tapered tip (7-9
m) is presented. Next, the optimization of the separationparameters by varying the C18 stationary-phase particlesize (3 versus 1.5 m), as well as mobile-phase composition including acetonitrile (ACN) volume fraction, ionicstrength, and pH is described. The optimized separationis achieved using 3-m C18 packing with 75% ACN (v/v),5 mM Tris at pH 8.0. Optimization for on-line CEC-ESI-MS detection is then done varying both the sheath liquidand spray chamber parameters while evaluating the useof random versus structured factorial table experimentaldesigns. The more structured approach allows fundamental analysis of individual ESI-MS parameters while minimizing CEC and MS equilibration time between settings.A comparison of CEC-ESI-MS to CEC-APCI-MS usingsimilar sheath and spray chamber conditions presentsnew insight for coupling of CEC to APCI-MS. The sheathliquid flow rate required to maintain adequate sensitivityis much higher in APCI source (50 L/min) as comparedto the ESI source (3 L/min). The on-line mass spectraobtained in the full scan mode show that fragmentationin the two sources occurs at different positions on theZwittergent molecules. For ESI-MS, the protonated molecular ion is always highest in abundance with minorfragmentation occurring due to the loss of the alkyl chain.In contrast, the APCI-MS spectra show that the highestabundant ion resulted by elimination of propane sulfonatefrom the Zwittergent molecule. A comparison of thesensitivity between the two sources in positive ionizationSIM mode shows that CEC-ESI-MS provides an impressive limit of detection (LOD) of 5 ng/mL, which is at least3 orders of magnitude lower than CEC-APCI-MS (LOD100 g/mL). Finally, the optimized CEC-MS methodscomparing ESI and APCI are applied for separation andstructural characterization of a real industrial zwittergentsample, Rewoteric AM CAS.
m) is presented. Next, the optimization of the separationparameters by varying the C18 stationary-phase particlesize (3 versus 1.5 m), as well as mobile-phase composition including acetonitrile (ACN) volume fraction, ionicstrength, and pH is described. The optimized separationis achieved using 3-m C18 packing with 75% ACN (v/v),5 mM Tris at pH 8.0. Optimization for on-line CEC-ESI-MS detection is then done varying both the sheath liquidand spray chamber parameters while evaluating the useof random versus structured factorial table experimentaldesigns. The more structured approach allows fundamental analysis of individual ESI-MS parameters while minimizing CEC and MS equilibration time between settings.A comparison of CEC-ESI-MS to CEC-APCI-MS usingsimilar sheath and spray chamber conditions presentsnew insight for coupling of CEC to APCI-MS. The sheathliquid flow rate required to maintain adequate sensitivityis much higher in APCI source (50 L/min) as comparedto the ESI source (3 L/min). The on-line mass spectraobtained in the full scan mode show that fragmentationin the two sources occurs at different positions on theZwittergent molecules. For ESI-MS, the protonated molecular ion is always highest in abundance with minorfragmentation occurring due to the loss of the alkyl chain.In contrast, the APCI-MS spectra show that the highestabundant ion resulted by elimination of propane sulfonatefrom the Zwittergent molecule. A comparison of thesensitivity between the two sources in positive ionizationSIM mode shows that CEC-ESI-MS provides an impressive limit of detection (LOD) of 5 ng/mL, which is at least3 orders of magnitude lower than CEC-APCI-MS (LOD100 g/mL). Finally, the optimized CEC-MS methodscomparing ESI and APCI are applied for separation andstructural characterization of a real industrial zwittergentsample, Rewoteric AM CAS.