Fabrication of Internally Tapered Capillaries for Capillary Electrochromatography Electrospray Ionization Mass Spectrometry
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- 作者：Jack Zheng ; Dean Norton ; and Shahab A. Shamsi
- 刊名：Analytical Chemistry
- 出版年：2006
- 出版时间：February 15, 2006
- 年：2006
- 卷：78
- 期：4
- 页码：1323 - 1330
- 全文大小：315K
- 年卷期：v.78,no.4(February 15, 2006)
- ISSN：1520-6882
文摘
In this study, we report a novel procedure for fabricatinginternally tapered capillary columns suitable for thecoupling of capillary electrochromatography (CEC) toelectrospray mass spectrometry (ESI-MS). The internaltapers were prepared by slowly heating the capillary endin a methane/O2 flame. Due to continuous self-shrinkingof the inner channel of the capillary, the inside diameterof the opening was reduced to 7-10 
m. The procedureis easy to handle, with no requirement for expensiveequipment as well as elimination of problematic grindingof the tip. Several advantages of these new internal tapers,as compared to using externally tapered columns, aredescribed. First, the problems of poor durability and tipbreakage associated with external tapering were successfully overcome with the internal taper. A comparison ofthe online CEC/ESI-MS between external versus internaltapers showed that the latter provides enhanced electrospray stability, resulting in significantly lower short-termnoise and very short-term noise values. In turn, the morerugged design of internal tapers allows performing CEC/MS utilizing a harsh polar organic mobile phase, whichwas not previously successful using an external taper dueto higher operating current and electrospray arcing. Next,data on the reproducibility of the internally tapered CEC/MS column using warfarin and 
-blockers as modelanalytes are presented. For example, when comparing thereproducibility for separation of warfarin under reversed-phase conditions, the internal taper demonstrated superior intraday % RSD (1.6-3.4) as compared to theexternal taper intraday % RSD (5-6). Last, the applicability of performing quantitative CEC/MS with internallytapered capillaries is demonstrated for simultaneousenantioseparation of -blockers. Impressive quantitativeresults include good linearity of calibration curves (e.g.,R2 = 0.9940-0.9988) and limit of detection as low as30 nM. The sensitive detection of a minor impurity of oneenantiomer at the 0.1% level in a major chiral entitybuttresses the suitability of compliance with FDA guidelines.
m. The procedureis easy to handle, with no requirement for expensiveequipment as well as elimination of problematic grindingof the tip. Several advantages of these new internal tapers,as compared to using externally tapered columns, aredescribed. First, the problems of poor durability and tipbreakage associated with external tapering were successfully overcome with the internal taper. A comparison ofthe online CEC/ESI-MS between external versus internaltapers showed that the latter provides enhanced electrospray stability, resulting in significantly lower short-termnoise and very short-term noise values. In turn, the morerugged design of internal tapers allows performing CEC/MS utilizing a harsh polar organic mobile phase, whichwas not previously successful using an external taper dueto higher operating current and electrospray arcing. Next,data on the reproducibility of the internally tapered CEC/MS column using warfarin and -blockers as modelanalytes are presented. For example, when comparing thereproducibility for separation of warfarin under reversed-phase conditions, the internal taper demonstrated superior intraday % RSD (1.6-3.4) as compared to theexternal taper intraday % RSD (5-6). Last, the applicability of performing quantitative CEC/MS with internallytapered capillaries is demonstrated for simultaneousenantioseparation of -blockers. Impressive quantitativeresults include good linearity of calibration curves (e.g.,R2 = 0.9940-0.9988) and limit of detection as low as30 nM. The sensitive detection of a minor impurity of oneenantiomer at the 0.1% level in a major chiral entitybuttresses the suitability of compliance with FDA guidelines.