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To alleviate ion suppression from phosphate buffer and to preserve separation integrity, a new capillary electrophoresis mass spectrometry (CE--MS) interface was developed. The interface consisted of a low-flow interface and a liquid junction. In this design, both the inlet reservoir and the liquid-junction reservoir were filled with phosphate running buffer. Because the phosphate anions in the column migrated toward the inlet reservoir (away from the electrospray ionization (ESI) source) the problem of ion suppression in ESI was avoided. The liquid junction was incorporated to eliminate issues of degraded separation observed when sheath liquid interfaces use different buffers for separation and MS analysis attributed to differences in anion velocity. The utility of the interface was demonstrated by the analysis of antihistamines at pH 3.5 and the analysis of perfluorocarboxylic acid at pH 9.5.

A four-channel multiplexed electrospray capillary electrophoresis interface has been developed. This new interface permits up to four capillary electrophoresis columns to be sampled sequentially by means of a stepper motor and a notched rotating plate assembly, which at any instant occludes all but a single sprayer. In this design, four sheath liquid electrospray probes are oriented in a circular array situated 90[degrees] relative to one another. The rotating metal disk, which contains a one-quarter notch, is mounted to the stepper motor assembly and is located between the sprayers and the entrance aperture of an ion trap mass spectrometer. By using the data acquisition signal from the ion trap mass spectrometer, the scan event is synchronized with the rotation of the metal disk. With this device, four discrete sample streams can be simultaneously analyzed, resulting in a 4-fold increase in analytical throughput.

A robust interface has been developed for interfacing micellar electrokinetic chromatography (MEKC) and nonvolatile buffer capillary electrophoresis (CE) to electrospray ionization mass spectrometry (ESI-MS). The interface consists of two parallel capillaries for separation (50 [micro]m i.d. x 155 [micro]m o.d.) and makeup (50 [micro]m i.d. x 155 [micro]m o.d.) housed within a larger capillary (530 [micro]m i.d. x 690 [micro]m o.d.). The capillaries terminate in a single tapered tip having a beveled edge. The use of a tapered beveled edge results in a greater tip orifice diameter (75 [micro]m) than in a previous design from our laboratory (25 [micro]m) that used a flat tip. While maintaining a similar optimum flow rate and consequently similar sample dilution, a 75-[micro]m beveled emitter is more rugged than a 25-[micro]m flat tip. Furthermore, the incorporation of a sheath liquid capillary allows the compositions of the final spray solution to be controlled. The application of this novel CE/ESI-MS interface was demonstrated for MEKC using mixtures of triazines (positive ion mode) and phenols (negative ion mode). The ability to perform CE/ESI-MS using a nonvolatile buffer was demonstrated by the analysis of gangliosides with a buffer consisting of 40 mM borate and 20 mM [alpha]-cyclodextrin.

A simple and versatile low-flow interface has been developed for interfacing capillary electrophoresis (CE) with electrospray ionization (ESI) mass spectrometry. This low-flow interface showed better sensitivity than a conventional sheath liquid interface, primarily attributed to a low dilution factor and a reduction in the sprayer orifice size. The interface was also found to be more tolerant to the presence of nonvolatile salts. Because of tolerance to the surfactant SDS, this interface can be used to couple micellar electrokinetic chromatography (MEKC) with ESI-MS. The performance of the interface in an MEKC-MS application, as demonstrated in the analysis of triazines, was significantly better than that obtained with a conventional sheath liquid interface. Moreover, this interface can be easily used for large-volume sample-stacking (LVSS) applications. Using a series of phenols as a test case, an approximate 500-fold enrichment was achieved by LVSS in conjunction with the low-flow CE/MS interface described.

Plasma desorption mass spectrometry (PDMS) can be applied in determining the molecular weight and the heterogeneity observed in human interleukin-4 glycoprotein. This study requires the evaluation of PDMS results with the use of sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis. The results indicate that PDMS provides direct measurement of intact glycoproteins exhibiting more than 10% carbohydrate.

A tapered capillary tip containing a beveled edge was developed for use in sheathless capillary electrophoresis/ electrospray mass spectrometry (CE/ESI-MS). The optimal flow rate of a 75-[micro]m-i.d., 90-[micro]m-o.d. beveled tapered capillary tip was similar to a conventional flat tapered tip with a 25-[micro]m orifice. Using a mixture of coptisine, berberine, and palmatine chloride, the sheathless CE/ ESI-MS sensitivity of a beveled 75[micro]m tapered tip capillary was found to be similar to a 25[micro] m flat tip. Although both tips offer similar CE/ESI-MS sensitivity, the beveled tapered capillary tip is more rugged and durable than a conventional 25-[micro]m tapered capillary because of the larger outside diameter and inside diameter. To make electrical contact, the capillary tip was smeared with paint marker followed by the application of a carbon coating using a graphite pencil. Using this refined carbon-coating procedure, the capillary tip can be operated with aprotic solvents.