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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 method based on the analysis of trimethylsilyl (TMS) derivatives by capillary gas chromatography electrospray ionizationmass spectrometry (GC-ESI/MS) was proposed. To improve separation, analytes were derivatized to their TMS derivative. During ESI analysis, TMS derivatives may hydrolyze back to their polar native form and are thus suitable for ESI analysis. Several types of analytes were studied to investigate the potential of the approach. Not all TMS derivatives hydrolyzed back to their native form as anticipated. Incomplete hydrolysis was observed for TMS-organic acids and TMS-nonchlorinated phenols. For TMSchlorophenols, the observation of only the [M-H]-ion suggested that these phenols were hydrolyzed back to their native form. For TMS-beta agonists, the hydrolysis rate was low; therefore, the hydrolysis product was not detected. Both TMS-chlorophenols and TMS-beta agonists provide a sensitivity in the range of low parts per billion (0.25-5 ng/ml and 0.5-10ng/ml respectively). [ABSTRACT FROM AUTHOR]

RATIONALE A comparative strategy has been demonstrated using RNase B, a single-site N-linked high-mannose glycoprotein. Glycoproteins are more common with multiple glycosylation sites and with complex glycans. A strategy capable of differentiating the changes caused by glycoprotein concentration, glycosylation site occupancy, and a glycoform profile of complex glycoproteins would be beneficial. METHODS Tryptic-digested glycoproteins were labeled using 12C,H-formaldehyde and 13C, D-formaldehyde, purified, and then analyzed using capillary reversed-phase liquid chromatography/mass spectrometry (RPLC/MS). The relative intensity of non-glycosylated peptides provided information on glycoprotein concentration variation. A site-specific glycoform profile variation was obtained by comparing the glycoform profile of CH2 and 13CD2 glycopeptides. Determining the protein concentration and glycoform profile variations allows the glycosylation site occupancy variation to be calculated. RESULTS A strong correlation between the observed and prepared ratios for fetuin glycopeptides from 0.2 to 5 was obtained. Two fetuin samples with different glycoprotein concentrations (4-fold change), glycoform profiles (normal and modified), and glycosylation site occupancies (100% and 50%) were prepared, labeled, mixed, purified, and analyzed using RPLC/MS. The results of the comparative study had a strong correlation with the prepared values. CONCLUSIONS In this report, we demonstrated a comparative analysis of fetuin, a glycoprotein with multiple glycosylation sites and complex sialyl glycans. Compared to our previous approach, we made several modifications including the use of RPLC, a larger mass difference isotope tag, and isotope overlapping correction. The modified approach is expected to be applicable to most glycoproteins. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, we propose a simple strategy based on flow injection and field-amplified sample-stacking CE- ESI- MS/ MS to analyze haloacetic acids ( HAAs) in tap water. Tap water was passed through a desalination cartridge before field-amplified sample-stacking CE- ESI- MS/ MS analysis to reduce sample salinity. With this treatment, the signals of the HAAs increased 300- to 1400-fold. The LODs for tap water analysis were in the range of 10 to 100 ng/L, except for the LOD of monochloroacetic acid (1 μg/L in selected-ion monitoring mode detection). The proposed method is fast, convenient, and sensitive enough to perform on-line analysis of five HAAs in the tap water of Taipei City. Four HAAs, including trichloroacetic acid, dichloroacetic acid, dibromoacetic acid, and monobromoacetic acid, were detected at concentrations of approximately 1.74, 1.15, 0.16, and 0.15 ppb, respectively. [ABSTRACT FROM AUTHOR]

A fast CEC-MS approach based on a microinjector and a short CEC column was developed. Poly(dimethylsiloxane) was used as the substrate for microinjector fabrication. A short capillary column (∼5 cm) packed with 5 μm octadecyl silica particles was inserted into the microinjector. The microinjector CEC device was interfaced to ESI-MS using a low-flow sheath liquid interface. The device delivers the advantages of sample introduction, pre-concentration, elution, and fast analysis as in chip-CEC yet avoids the difficulty of packing stationary material into the chip. The online pre-concentration and CEC-MS analysis capabilities of this device were demonstrated by analysis of a six-triazine mixture. A signal enhancement of 20-99-fold was achieved with a sample loading time of 180 s. [ABSTRACT FROM AUTHOR]

A new cyclitol which is abudant in the late developmental stages of leucaena (Leucaena leucocephala (Lam.) de Wit) seeds was identified by HPLC, NMR, and GC-MS as O-α-D-galactopyranosyl-(1 → 1)-3-O-methyl-D-chiro-inositol, a new galactopinitol. This galactopinitol was initially detected midway through seed development and increased to 10.2 mg (g DW)-1, but decreased in mature seeds to its about a half. Stachyose content increased greatly and remained the most abundant of the soluble sugars in mature seeds (25.6 mg (g DW)-1). Artifical drying at 73% relative humidity of 70 DPA immature seeds induced the accumulation of raffinose, stachyose, galactopinitol and galactinol, but the total amounts of these sugars were only about half of those found in mature seeds. Seed germination decreased following an initial increase after 8 d artitifical drying to a moisture content of 24%, and this dehydration damage probably is because of underdevelopment of seed tissue. Galactopinitol changes in a similar fashion to the oligosaccharides during the late developmental stage and dehydration experiment, implying that galactopinitol may play a role in desiccation tolerance of leucaena seeds. [ABSTRACT FROM AUTHOR]

Hydrogen radical/molecule reactions are postulated to rationalize the formation of major fragment ions in the methane negative and positive chemical ionization mass spectrometry of the dicyanomethane derivatives of 9-fluorenone and benzophenone. Evidence for the formation of [M + H]− anions that are not represented by significant peaks in the mass spectra is provided by mass spectra of deuterium-labeled analogs and by tandem mass spectrometry studies of the [M + 1]− anions of the analyte. [ABSTRACT FROM AUTHOR]

The dicyanomethylene derivative of a benzophenone analog significantly alters the fragmentation pattern observed during electron impact ionization of the underivatized parent compound. A double bond connecting the dicyanomethylene moiety to the parent compound is cleaved during a major fragmentation pathway for many of these compounds. A mechanism involving rearrangement of two hydrogen atoms is proposed to rationalize cleavage of this double bond. Conventional mass spectra as well as collisionally activated dissociation mass spectra of selected ions of several model compounds are reported and described in support of a proposed fragmentation mechanism. [ABSTRACT FROM AUTHOR]