Analysis of neutral drugs in human plasma by fluoride attachment in liquid chromatography/negative ion electrospray tandem mass spectrometry.

The analysis of several neutral drugs, mephenesin, guaifenesin, simvastatin, podophyllotoxin and inositol, was accomplished by negative ion electrospray ionization mass spectrometry (ESI-MS) using adduct formation with three different halide ions. The fluoride, chloride and bromide adducts of the selected drugs exhibited intense signals in negative ion ESI. Under collision-induced dissociation, the major product ions of bromide and chloride adducts were the nonspecific bromide and chloride anions, respectively. In contrast, fluoride adducts produced strong [M--H](-) ions as well as product ions with good intensity. Fluoride attachment liquid chromatography/negative ion electrospray tandem mass spectrometry (LC/ESI-MS/MS) was applied to the analysis of the selected neutral drugs in human plasma. Detection limits in the range of 0.025-0.05 ng/mL were achieved using 0.5 mL plasma. Good linearity was observed for each of the drugs examined in human plasma over the range of 0.05-50 ng/mL.

Application of pentafluorophenyl hydrazine derivatives to the analysis of nabumetone and testosterone in human plasma by liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.

Two carbonyl compounds, nabumetone and testosterone, were derivatized with pentafluorophenyl hydrazine (PFPH) and analyzed by atmospheric-pressure chemical-ionization mass spectrometry. The PFPH derivatives underwent dissociative electron capture in negative-ion APCI (ECAPCI) and gave intense [M-20](-) ions in the mass spectra. In positive-ion APCI, the PFPH derivatives underwent efficient protonation and gave intense [M + H](+) ions in the mass spectra. In CID, the major product ions of the [M-20](-) ions in ECAPCI corresponded to the partial moiety of PFPH. In contrast, the major product ions of [M + H](+) corresponded to the partial moiety of the analyte. By using selected reaction monitoring (SRM) detection, low pg of nabumetone (1 pg) and testosterone (7 pg) could be detected in both ECAPCI and positive-ion APCI. In comparison with the detection limits (SRM) of the underivatized analytes, use of the PFPH derivatives resulted in 2500-fold and 35-fold sensitivity enhancements for nabumetone and testosterone, respectively. The PFPH derivatives were applied to the analysis of nabumetone and testosterone in human plasma by both ECAPCI and positive-ion APCI and were found to enable detection of 0.1 ng mL(-1) nabumetone in spiked plasma. For testosterone, endogenous testosterone in female plasma was detected in both ECAPCI and positive-ion APCI.

Sheathless capillary electrophoresis/electrospray mass spectrometry using a carbon-coated tapered fused-silica capillary with a beveled edge.

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-microm-i.d., 90-microm-o.d. beveled tapered capillary tip was similar to a conventional flat tapered tip with a 25-microm orifice. Using a mixture of coptisine, berberine, and palmatine chloride, the sheathless CE/ ESI-MS sensitivity of a beveled 75 microm tapered tip capillary was found to be similar to a 25 microm 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-microm 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.

On-line monitoring of trihalomethanes in drinking water using continuous-flow purge and cryofocusing gas chromatography-mass spectrometry.

A continuous-flow purge-and-trap-GC-MS system was developed for on-line monitoring of THMs (trihalomethanes) in drinking water. Three systems with different traps and purging flow-rates are discussed. In order to minimize interference from water vapor, total purge gas volume and injection temperature were controlled during analysis. Shorter sample concentration time and GC separation time reduced total cycle time to less than 5 min. The detection limits of the system could be lowered to 10 ppt, 25 ppt, 40 ppt, and 50 ppt (w/w) for CHCl3, CHCl2Br, CHClBr2, and CHBr3, respectively. This system could detect changes in sample concentration when applied to the on-line monitoring of THMs in drinking water.

Analysis of synthetic chemical drugs in adulterated Chinese medicines by capillary electrophoresis/electrospray ionization mass spectrometry.

Sixteen synthetic chemical drugs, often found in adulterated Chinese medicines, were studied by capillary electrophoresis/UV absorbance (CE/UV) and capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS). Only nine peaks were detected with CZE/UV, but on-line CZE/MS provided clear identification for most compounds. For a real sample of a Chinese medicinal preparation, a few adulterants were identified by their migration times and protonated molecular ions. For coeluting compounds, more reliable identification was achieved by MS/MS in selected reaction monitoring mode. Micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate (SDS) provided better separation than capillary zone electrophoresis (CZE), and, under optimal conditions, fourteen peaks were detected using UV detection. In ESI, the interference of SDS was less severe in positive ion mode than in negative ion mode. Up to 20 mM SDS could be used in direct coupling of MEKC with ESI-MS if the mass spectrometer was operated in positive ion mode. Because of better resolution in MEKC, adulterants can be identified without the use of MS/MS.

Proton-lithium binding behavior of tris(2-((pyrid-2-ylmethyl)uredio)ethyl)amine.

Tris(2-((pyrid-2-ylmethyl)uredio)ethyl)amine (2) and its perchlorate salt, 2.HClO(4), bind with Li+ in nitromethane in a 1:1 fashion. The stability constants of K(Li+) and K(H)(Li+) were found to be 112 +/- 25 and 130 +/- 30 M(-)(1) in CD(3)NO(2), respectively. Formation of the 1:1 complexes were further evidenced by electrospray ionization mass spectrometry (ESI-MS). The slight increase, or at least the same order of magnitude, of K(H)(Li+) compared to K(Li+) points to a remarkable preorganization of the protonated podand in 2.HClO(4), that essentially overcomes the increased Columbic repulsion occurring on complexation to Li+.

Analysis of phospholipase A2 glycosylation patterns from venom of individual bees by capillary electrophoresis/electrospray ionization mass spectrometry using an ion trap mass spectrometer.

A method based on tryptic digestion, ultrafiltration and capillary electrophoresis/mass spectrometry (CE/MS) has been developed for the analysis of the glycosylation pattern in the phospholipase A2 (PLA) of individual honeybees. Without reducing the disulfide bonds, PLA was digested with trypsin and filtered with a 3 kDa molecular weight (MW) cut-off membrane. With this procedure, the glycopeptides could be isolated from the nonglycosylated peptides. After tryptic digestion and ultrafiltration, the disulfide bonds were reduced before analysis by CE. To reduce the adsorption, CE separation was performed on successive multiple ionic-polymer (SMIL) polybrene (PB) coated capillary columns. The SMIL-PB columns allowed partial separation of the glycopeptides and eight glycopeptides were identified by on-line coupling of CE with electrospray ionization (ESI) mass spectrometry. The analysis of phospholipase A2 from the venom of individual bees indicated that the variation and relative abundances of different glycopeptides were similar between the younger and the older bees.

On-line monitoring trihalomethanes in chlorinated water by membrane introduction-fast gas chromatography mass-spectrometry.

An analytical method based on membrane introduction and fast gas chromatography-mass spectrometry (GC-MS) has been developed for the on-line monitoring of trihatomethanes (THMs) in chlorinated drinking water. The coupling of membrane introduction with fast GC-MS offers the advantage of membrane introduction as an on-line sampling device and fast GC-MS as a separation and identification method. While maintaining the on-line monitoring characteristic of traditional membrane introduction mass spectrometry (MIMS), the difficulty of distinguishing CHCl3 and CHBrCl2 in MIMS was overcome by rapid GC separation and MS analysis. Water permeated across the membrane affected the analysis of CHBr2Cl and CHBr3. A method based on controlling the injection temperature and injection time has been developed to overcome the moisture problem. This method is simple and less time consuming than the conventional moisture removing method. Under typical operating conditions, the sampling rate was about 20 samples h(-1) capable of on-line monitoring THMs in chlorinated drinking water. The detection limits of this system were found to be about 2 ppt, 4 ppt, 4 ppt, and 8 ppt for CHCl3 CHBrCl2, CHBr2Cl, and CHBr3, respectively.

Structural analysis of chromophore-labeled disaccharides by capillary electrophoresis tandem mass spectrometry using ion trap mass spectrometry.

Disaccharides tagged with p-aminobenzoic acid (ABA) were separated by capillary electrophoresis (CE) and analyzed on-line with negative ion electrospray ionization tandem mass spectrometry (ESI/MS/MS). The formation of glycosylamine instead of reductive amination was selected as the derivatization reaction. In negative ion ESI, the glycosylamine approach provides more information on linkage and anomeric configuration than reductive amination. In CE analysis of ABA-labeled disaccharides, alpha-cyclodextrin (CD) was found to play a crucial role in the separation of linkage isomers. Although ammonium acetate/alpha-CD provided the best resolution of linkage isomers, the borate buffer was superior to alpha-CD in the separation of disaccharides with the same linkage but different anomeric configuration and/or monosaccharide composition. Both alpha-CD and borate suppressed the ion signal in ESI, and operational conditions were successfully obtained using 10 mM alpha-CD or 10 mM borate.

Analysis of a commercial preparation of erythromycin estolates by tandem mass spectrometry and high performance liquid chromatography/electrospray ionization tandem mass spectrometry using an ion trap mass spectrometer.

Because of the lack of a UV chromophore and their much smaller abundances in comparison with the major component, the minor components in erythromycin estolate preparations are difficult to analyze by high performance liquid chromatography ultraviolet (HPLC-UV). Tentative assignment of the major and minor components can be achieved with the combination of full scan and ZoomScan using an ion trap mass spectrometer. Tandem mass spectrometry (MS/MS) provided an effective method to quickly identify most components without chromatographic separation, and all the related compounds, except the isobaric pair ECE and PdMeEA, could be identified in this way. The best result was obtained by using liquid chromatography/tandem mass spectrometry (LC/MS/MS) operated in selected reaction monitoring mode. The major compound, the estolate of erythromycin A (EAE), and seven other minor components, could be separated and identified, with semiquantitative estimates of relative concentrations.

Analysis of coptisine, berberine and palmatine in adulterated Chinese medicine by capillary electrophoresis-electrospray ion trap mass spectrometry.

Chinese medicine preparations contaminated with coptisine, berberine and palmatine were studied by capillary electrophoresis-electrospray ion trap mass spectrometry. The dubious adulterants were identified by their retention times, molecular ions and specific fragment ions produced from collision induced dissociation. The results showed that, in comparison with CE-UV and capillary electrophoresis-electrospray mass spectrometry (CE-ESI-MS), more reliable identification could be achieved with CE-ESI-MS-MS using ion trap mass spectrometry.

Structural analysis of chromophore-labeled disaccharides and oligosaccharides by electrospray ionization mass spectrometry and high-performance liquid chromatography/electrospray ionization mass spectrometry.

Disaccharides and linear oligosaccharides were labeled with p-aminobenzoic ethyl ester (ABEE) chromophore and analyzed by negative ion electrospray ionization mass spectrometry (ESIMS). The formation of glycosylamines rather than reductive amination in the labeling reaction produced many characteristic fragment ions under in source collision-induced dissociation (CID). These ions provided unambiguous assignment of the position of the glycosidic linkages. This approach was extended to the analysis of linkages and the sequence of the linkages of several linear oligosaccharides. Additionally, the anomeric configuration of ABEE-labeled 1-3-, 1-4- and 1-6-linked glucose disaccharides could be differentiated according to the relative abundance of characteristic ions. Disaccharides with the same linkage but different monosaccharide compositions could be analyzed by on-line coupling of high-performance liquid chromatography with ESIMS.

Analysis of gangliosides by capillary zone electrophoresis and capillary zone electrophoresis-electrospray mass spectrometry.

Gangliosides, sialic acid(s)-containing glycosphingolipids, were separated by capillary zone electrophoresis and detected with either UV or electrospray mass spectrometry. Several electrolyte system were evaluated for the separation of underivatized gangliosides. The best result was obtained by using 50 mM borate and 50 mM phosphate buffer containing 20 mM alpha-cyclodextrin at pH 9.9. The four major ganglioside forms (GM1, GD1a, GD1b, GT1b) were successfully separated, and, moreover, each ganglioside yielded two peaks, splitting by the difference in chain length of the ceramide moiety. The resolution obtained in CE-UV could not be reproduced in CE-MS because of the incompatibility of the borate/phosphate buffer to ESI-MS. With the use of more volatile buffers, such as ammonium acetate or 2-[N-cyclohexylamino]-ethanesulfonic acid, baseline resolution was obtained for gangliosides having different number of sugars, but the two disialoganglioside isomers, GD1a and GD1b, were coeluted.

Occurrence of a novel galactopinitol and its changes with other non-reducing sugars during development of Leucaena laucocephala seeds.

A new cyclitol which is abundant in the late developmental stages of leucaena (Leucaena leucocephala (Lam.) de Wit) seeds was identified by HPLC, NMR, and GC-MS as O-alpha-D-galactopyranosyl-(1-->1)-3-O-methyl-D-chiroinositol, a new galactopinitol. This galactopinitol was initially detected midway through seed development and increased to 10.2 mg (gDW)-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). Artificial 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 artificial 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.

High-energy collision-induced dissociation of ceramide ions from permethylated glycosphingolipids.

Ceramide fragments from permethylated glycosphingolipids (GSLs) were studied by highenergy collision-induced dissociation (CID). In comparison with ceramlde fragments of underivatized GSLs, many more product ions including charge-remote fragment ions were observed. These ions provided detailed structural information on the ceramides. The relative intensity and the mass interval between the L and M ions were used to assign the position of the double bond. The position of the hydroxyl group was assigned with the Ln and K ions. Because the ceramide fragments and not the pseudomolecular ions were selected as the precursor ions, the size of GSLs had little effect on the quality of the product ion spectra. The sensitivity of this approach was in the range of picomoles.

Student's exposure to volatile organic compounds while commuting by motorcycle and bus in Taipei City.

This study examined student's exposure to volatile organic compounds (VOCs) while commuting by bus and motorcycle in Taipei, Taiwan in the winter of 1992. A total of 19 target C5-C10 VOCs on three most frequently used commuting routes were collected on Tenax-GC adsorbent tubes. The VOCs were desorbed by thermal desorption method and analyzed by GC-MS. The most abundant VOC exposure experienced by commuters was to toluene. Several alkylated benzenes, such as propyl benzenes, ethyl-methyl-benzenes and trimethyl-benzenes, were relatively abundant on the roads in Taipei. The mean benzene concentration measured in buses was 173 micrograms/m3 and motorcycles. On the average, the commuters in Taipei experienced about three to eight times higher VOC concentrations than the commuters in Los Angeles, California. Higher VOC concentrations were measured on motorcycles than in buses. The VOC concentrations were not significantly different between morning and afternoon commutes, nor among the three commuting routes. VOC concentrations measured in classroom at three schools in downtown Taipei did not vary significantly on each sampling day. However, at each school the in-classroom VOC concentrations varied significantly over the six consecutive sampling days. The VOC concentrations measured on the roads were about five times higher than those measured in the school classrooms in the city. Moderate to high correlations were found among most of the measurements of the 19 VOCs. The survey questionnaire indicated that daily commuting time ranged from 45 minutes for elementary school students to 95 minutes for vocational school students.(ABSTRACT TRUNCATED AT 250 WORDS)

Linkage analysis of chromophore-labeled disaccharides and linear oligosaccharides by negative ion fast atom bombardment ionization and collisional-induced dissociation with B/E scanning.

Negative ion fast atom bombardment ionization in combination with collisional-induced dissociation mass spectrometry differentiates the linkage position(s) of chromophore-labeled di- and oligosaccharides. The formation of glycosylamines rather than the more popular reductive amination has been used to label the reducing end of sugars with ultraviolet or fluorescence tags. Two types of fragment ions were detected, one with the charge carried on the chromophore end and the other with the charge carried on the nonreducing terminus. These ions are essential to the determination of interglycosidic linkage and they are produced from the ring cleavage of the reducing end monosaccharide. Additionally, the anomeric configuration of the 1-4-linked residue could be assigned according to the relative abundance of the fragment ions.

Mastoparan B, synthesis and its physical and biological properties.

Mastoparan B, a tetradecapeptide toxin (LKLKSIVSWAKKVL) isolated from the hornet (Vespa basalis) venom, was synthesized chemically. The physical and biological properties of both the native and synthetic peptides were studied and proved to be identical. Mastoparan B was found to have a potent antibacterial activity to both Gram negative and Gram positive bacteria.

Urinary organic acid profiles in fatty Zucker rats: indications for impaired oxidation of butyrate and hexanoate.

The urinary excretion of 45 organic acids, monitored by gas-liquid chromatography, was compared in fatty (fa/fa) and lean (Fa/?) Zucker rats maintained on a chemically simplified diet. At the age of 6, 16, and 22 weeks, fatty rats excreted more of the various organic acids than their lean counterparts. However, the greatest difference was in the excretion of ethylmalonate, even when excretion data were normalized to body weight. The next highest excretion difference was in adipate and an unknown compound, and the third highest in pyruvate. A second group of rats examined at 7 weeks also excreted an excess of these four acids, as well as glucuronate and indole-3-acetate. The excessive excretion of ethylmalonate and adipate, which is characteristic of human genetic defects in short- and medium-chain fatty acid oxidation, suggested that the oxidation of butyrate and hexanoate might be impaired in the fatty rat. Thus, as a test of their capacity to oxidize medium- and short-chain fatty acids, two groups of fatty and lean rats were transferred to diets enriched with either trioctanoylglyceride, a medium-chain triglyceride (MCT), or sodium butyrate, a short-chain fatty acid. Both lean and fatty rats on the MCT diet, but only the lean rats on the butyrate-enriched diet, increased their excretion of adipate. However, on both the MCT and butyrate diet, ethylmalonate excretion increased only in lean rats, almost reaching amounts found previously in fatty rats. These results suggest that the fatty rat has an impairment of the beta-oxidation of butyrate and hexanoate, a defect that might increase intracellular concentrations of butyryl-CoA, the optimal primer for the synthesis of long-chain fatty acids.