Mass spectral behavior of the hydrolysis products of sesqui- and oxy-mustard type chemical warfare agents in atmospheric pressure chemical ionization

Bis(2-hydroxyethylthio)alkanes and bis(2-hydroxyethylthioalkyl)ethers are important biological and environmental degradation products of sulfur mustard analogs known as sesqui- and oxy-mustards. We used atmospheric pressure chemical ionization mass spectrometry (APCI MS) to acquire characteristic spectra of these compounds in positive and negative ionization modes. Positive APCI mass spectra exhibited [M + H](+); negative APCI MS generated [M + O(2)](-), [M - H](-), and [M - 3H](-); and both positive and negative APCI mass spectra contained fragment ions due to in-source collision-induced dissociation. Product ion scans confirmed the origin of fragment ions observed in single-stage MS. Although the spectra of these compounds were very similar, positive and negative APCI mass spectra of the oxy-mustard hydrolysis product, bis(2-hydroxyethylthiomethyl)ether, differed from the spectra of the other compounds in a manner that suggested a rearrangement to the sesqui-mustard hydrolysis product, bis(2-hydroxyethylthio)methane. We evaluated the [M + O(2)](-) adduct ion for quantification via liquid chromatography-MS/MS in the multiple-reaction monitoring (MRM) mode by constructing calibration curves from three precursor/product ion transitions for all the analytes. Analytical figures of merit generated from the calibration curves indicated the stability and suitability of these transitions for quantification at concentrations in the low ng/mL range. Thus, we are the first to propose a quantitative method predicated on the measurement of product ions generated from the superoxide adduct anion of the sesqui-and oxy-mustard hydrolysis products.     

Mass spectrometric investigation of gallium and zirconium complexes with octaethylporphyrin and tetraphenylporphyrin

Gallium and zirconium octaethylporphyrin (OEP) and tetraphenylporphyrin (TPP) were examined by electrospray ionization (ESI) mass spectrometry. All systems were prepared in dichloromethane with addition of a stabilizing lipophilic anionic agent, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB). In the solutions examined both monomeric and dimeric metalloporphyrins were observed. In the gallium-OEP mass spectrum the ion registered at m/z 601 was attributed to monomeric [Ga(OEP)](+) and that at m/z 1219 to the dimeric form, [[Ga(OEP)](2)OH](+). Peaks appearing in the ESI mass spectra of zirconium systems were substantially less intense, probably owing to the relatively low stability of complexes of this metal caused by its different geometry preferences. The most abundant monomeric zirconium-OEP complexes were [[Zr(OEP)OH]](+) (m/z 639) and [Zr(OEP)Cl](+) (m/z 657), and dimeric [[Zr(OEP)OH](2)](2+) (m/z 639). Analogous species were observed in the Zr(TPP) system: monomeric [[Zr(OEP)OH]](+) (m/z 719) and [Zr(TPP)Cl](+) (m/z 737) and dimeric [[Zr(TPP)OH](2)](2+) (m/z 719). In both cases series of other dimers, e.g. [[Zr(OEP)](2)O(2)H](+) (m/z 1277), [[Zr(OEP)OH](2)Cl](+) (m/z 1313), [Zr(TPP)(2)O(2)H](+), (m/z 1437), [[Zr(TPP)OH](2)OH](+) (m/z 1455) and [[Zr(TPP)OH](2)Cl](+) (m/z 1473), appeared. The results obtained confirmed the hypothesis concerning the formation of dimeric metalloporphyrins in solutions containing stabilizing lipophilic anions. It also allowed us to explain the super-Nernstian slopes of the calibration curves towards primary anions of ion-selective electrodes with membranes containing the examined metalloporphyrins.     

Electrospray mass spectrometry and tandem mass spectrometry of bimetallic oxovanadium complexes

A series of six bimetallic oxovanadium complexes (1-6; only one was purified) were investigated by electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) in negative-ion mode. Radical molecular anions [M](.-) were observed in MS mode. Fragmentation patterns of [M](.-) were proposed, and elemental compositions of most of the product ions were confirmed on the basis of the high-resolution ESI-CID-MS/MS spectra. A complicated series of low-abundance product ions similar to electron impact (EI) ionization spectra indicated the radical character of the precursor ions. Fragment ions at m/z 214, 200, and 182 seem to be the characteristic ions of bimetallic oxovanadium complexes. These ions implied the presence of a V-O-V bridge bond, which might contribute to stabilization of the radical. To obtain more information for structural elucidation, three representative bimetallic oxovanadium complexes (1-3) were analyzed further by MS in positive-ion mode. Positive-ion ESI-MS produced adduct ions of [M + H](+), [M + Na](+), and [M + K](+). The fragmentation patterns of [M + Na](+) were different than those of radical molecular anions [M](.-). Relatively simple fragmentation occurred for [M + Na](+), possibly due to even-electron ion character. Negative-ion MS and MS/MS spectra of the hydrolysis product of Complex 1 supported these finding, in particular, the existence of a V-O-V bridge bond.     

Nitramine anion fragmentation: A mass spectrometric and Ab initio study

The fragment ion formation characteristics of the radical anions generated from hexahydro-1,3,5-trinitrotriazine (RDX) and its three nitroso metabolites were studied using GC/MS with negative chemical ionization (NCI) to understand the fragmentation mechanisms responsible for the formation of the most abundant ions observed in their NCI mass spectra. Ab initio and density functional theory calculations were used to calculate relative free energies for different fragment ion structures suggested by the m/z values of the most abundant ions observed in the NCI mass spectra. The NCI mass spectra of the four nitramines are dominated by ions formed by the cleavage of nitrogen-nitrogen and carbon-nitrogen bonds in the atrazine ring. The most abundant anions in the NCI mass spectra of these nitramines have the general formulas C(2)H(4)N(3)O (m/z 86) and C(2)H(4)N(3)O(2) (m/z 102). The analyses of isotope-labeled standards indicate that these two ions are formed by neutral losses that include two exocylic nitrogens and one atrazine ring nitrogen. Our calculations and observations of the nitramine mass spectra suggest that the m/z 86 and m/z 102 ions are formed from either the (M--NO)(-) or (M--NO(2))(-) fragment anions by a single fragmentation reaction producing neutral losses of CH(2)N(2)O or CH(2)N(2)O(2) rather than a set of sequential reactions involving neutral losses of HNO(2) or HNO and HCN.     

Mass spectral fragmentation of the intravenous anesthetic propofol and structurally related phenols

Propofol (2,6-diisopropyl phenol) is a widely used intravenous anesthetic. To define its pharmacokinetics and pharmacodynamics, methods for its quantitation in biological matrixes have been developed, but its pattern of mass spectral fragmentation is unknown. We found that fragmentation of the [M - H](-) ion (m/z 177) of propofol in both APCI MS/MS and ESI MS/MS involves the stepwise loss of a methyl radical and a hydrogen radical from one isopropyl side chain to give the most intense product ion, [M -H - CH(4)](-), at m/z 161. This two-step process is also the preferred mode of fragmentation for similar branched alkyl substituted phenols. This mode of fragmentation of the [M - H](-) ion is supported by three independent lines of evidence: (1) the presence of the intermediary [M - H - CH(3)](-) radical ion under conditions of reduced collision energy, (2) the determination of the mass of the predominant [M - H - CH(4)](-) product ion by high resolution mass spectrometry, and (3) the pattern of product ions resulting from further fragmentation of the [M - H - CH(4)](-) product ion. Phenols with a single straight chain alkyl substituent, in contrast, undergo beta elimination of the alkyl radical irrespective of the length of the alkyl chain, yielding the most intense product ion at m/z 106. This product ion represents a special case of a stable intermediary radical for the two-step process described for branched side chains, because further elimination of a hydrogen radical from the beta carbon is not possible.     

Isotope edited product ion assignment by α-N labeling of peptides with [2H3(50%)]2,4-Dinitrofluorobenzene

An isotopic modification of Sanger's method for identifying peptide N-termini has been developed to assist peptide sequencing by tandem mass spectrometry. Tryptic peptides, such as Val-His-Leu-Thr-Pro-Val-Glu-Lys, are derivatized with an equimolar mixture of 2,4-dinitrofluorobenzene and [2H3]2,4-dinitrofluorobenzene. Under optimized derivatization conditions, the alpha-amino group could be derivatized while the epsilon-amine of the lysine side chain and the imidazole of histidine remained underivatized. The alpha-dinitrophenyl modified peptides were characterized by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) and liquid chromatography (LC)-ESI-MS. The [M + H]+ ions showed a doublet pattern with a delta m/z of 3 and the [M + 2H]2+ ions were recognized as doublets with a delta m/z of 1.5. MS/MS was employed where both isotopic [M + 2H]2+ ions were alternately subjected to collision-induced dissociation in the second quadrupole. Fragmentation in the ionization source generated identical product ion patterns that were observed during fragmentation in the second quadrupole. In the product ion mass spectra, the N-terminal a and b ions (no c ion observed) are doublets with a delta m/z of 3 or 1.5, while the C-terminal y and z ions (no x ion observed) are singlets appearing at identical masses. Thus, the product ions containing the N-terminus derivatized with a dinitrophenyl group are unequivocally distinguished from the product ions containing the C-terminus. The dinitrophenyl modification generally enhanced the production of a and b ions without diminishing y and z ion yields.     

Characterization of moenomycin antibiotics from medicated chicken feed by ion-trap mass spectrometry with electrospray ionization

The antimicrobial moenomycin, commonly used as a growth promoter in livestock, was isolated from medicated chicken feed. The purified extract was subjected to reversed-phase liquid chromatographic separation followed by structural characterization using ion-trap mass spectrometry (ITMS), which allowed identification of five moenomycins (A, A12, C1, C3, and C4) as the major components. The fragmentation patterns of the protonated and deprotonated moenomycin molecules, as well as of a series of sodium adducts, were investigated using ITMS after electrospray ionization. While the protonated molecules [M+H]+ proved highly unstable and underwent extensive in-source fragmentation, isolation and activation of the [M--H]- ions (m/z 1580 for moenomycin-A) yielded simple mass spectra with a dominant base peak corresponding to the loss of the carboxy-glycol and the C25-hydrocarbon chain (m/z 1152 for moenomycin-A). Further study of this fragment ion in an MS3 experiment gave rise to a peculiar product ion (m/z 902 for moenomycin-A) that was attributed to the expulsion of a carbohydrate moiety representing a central building block of the linear molecule. In positive ion mode the generation of the mono-sodiated adduct ions, [M+Na]+, was promoted by amending the mobile phase with 100 microM sodium acetate, but this also resulted in higher adducts of the type [M+2Na--H]+ and [M+3Na--2H]+ arising from the formation of the sodium salts of the phosphate acid diester and subsequently of the carboxylic acid. Substantial differences among the fragment-rich product ion profiles of the three species were observed, and could in part be traced back to the mode of complexation of the additional sodium cation(s).     

Is the hypothiocyanite anion (OSCN)- the major product in the peroxidase catalyzed oxidation of the thiocyanate anion (SCN)-? A joint experimental and theoretical study

The hypothiocyanate anion (OSCN)(-) is reported to be a major product of the lactoperoxidase/H(2)O(2)/(SCN)(-) system, and this anion is proposed to have significant antimicrobial properties. The collision induced (CID) negative ion mass spectrum of "(OSCN)(-)" has been reported: there is a pronounced parent anion at m/z 74, together with fragment anions at m/z 58 (SCN)(-) and 26 (CN)(-). These fragment anions are consistent with structure (OSCN)(-). However there is also a lesser peak at m/z 42 (OCN(-) or CNO(-)) in this spectrum which is either formed by rearrangement of (OSCN)(-) or from an isomer of this anion. The current theoretical investigation of (OSCN)(-) and related isomers, together with the study of possible rearrangements of these anions, indicates that ground-state singlet (OSCN)(-) is a stable species and that isomerization is unlikely. The three anions (OSCN)(-), (SCNO)(-), and (SNCO)(-) have been synthesized (in the ion source of a mass spectrometer) by unequivocal routes, and their structures have been confirmed by a consideration of their collision induced (negative ion) and charge reversal (positive ion) mass spectra. The CID mass spectrum of (SCNO)(-) shows formation of m/z 42 (CNO(-)), but the corresponding spectra of (OSCN)(-) or (SNCO)(-) lack peaks at m/z 42. Combined theoretical and experimental data support earlier evidence that the hypothiocyanite anion is a major oxidation product of the H(2)O(2)/(SCN)(-) system. However, the formation of m/z 42 in the reported CID spectrum of "(OSCN)(-)" does not originate from (OSCN)(-) but from another isomer, possibly (SCNO)(-).     

Tandem mass spectrometric approach for determining the structure of molecular species of ceramide in the marine sponge Haliclona cribricutis

Ceramides are important intracellular second messengers that play a role in the regulation of cell growth, differentiation and programmed cell death. Analysis of these second messengers requires sensitive and specific analytical method to detect individual ceramide species and to differentiate between them. Eight molecular species of ceramide were identified from the marine sponge Haliclona cribricutis using electrospray ionization tandem mass spectrometry (ESI-MS/MS). From this marine sponge N-hencicosanoyl (N21:0) to N-hexasanoyl (N26:0) Octadecasphing-4 (E)-enine have been reported for the first time. The ESI-MS spectra gave several strong protonated molecular ion [M+H](+) with the corresponding bis (2-ethyl hexyl) phthalate adduct [M+H+DHEP](+). The collision induced dissociation (CID) on ceramides at m/z 622.7337, 636.7645, 650.7789, 664.7925 and 678.8130 conducted at low-collision energy produced well characteristic product ions at m/z 252.31, 264.32, 278.33, 282.33 and 296 .35 for d18:1 sphingosine regardless of the length of the fatty chain. The MS/MS of the Phthalate adduct [M+H+DHEP](+) at m/z 1013.1820, 1027.1971, 1041.2176, 1055.2394 and 1069.2573 also yielded characterizing product ions for sphingosine and confirmed the molecular ion at m/z 391 for bis (2-ethyl hexyl) phthalate. The major ions in the [M+H](+) and [M+H+DHEP](+) were due to neutral loss of [M+H-H(2)O](+) and [M+H(H(2)O)(2)](+).     

4种儿茶素类化合物电喷雾质谱裂解规律的研究

利用离子阱飞行时间质谱仪的高质量精度、高分辨率及多级测定性能, 对儿茶素类化合物(二组对映异构体)质谱裂解进行研究, 并利用氢/氘交换法对裂解方式进行确证. 发现儿茶素对映异构体间具有相同的质谱裂解途径, 多级质谱无明显区别. 在二级质谱中, 表儿茶素/儿茶素(EC/C)丢失的CO₂发生在A环, 丢失的C₂H₂O发生在B环. ^1,4A^-, ^1,3A^-, ^1,2A^-和[M-H-B环]^-4个碎片离子为EC/C特征离子, 通过这4个离子质量数变化, 推测A环上的取代情况. 因表儿茶素没食子酸酯/儿茶素没食子酸酯(ECG/CG)结构上都含有没食子酸取代基, 在二级质谱中均可见m/z169特征峰, 此离子可用于ECG/CG和EC/C区分.     

Mass spectrometric analysis of leukotriene A4 and other chemically reactive metabolites of arachidonic acid

The biosynthesis of prostaglandins and leukotrienes proceeds through the formation of chemically reactive intermediates leukotriene A4 (LTA4) and prostaglandin H2 (PGH2) which in aqueous solutions have chemical half-lives of 3 s and 3 min, respectively. Prostacyclin (PGI2) is another chemically reactive prostanoid that has a chemical half-life of 3-4 min. The recent development of reversed phase HPLC stationary phases that are stable to elevated pH (pH 10-12) without significant column damage has permitted direct analysis of these acid-sensitive eicosanoids. Using electrospray ionization, molecular anions [M - H]- of these compounds were observed at m/z 317 for LTA4 and m/z 351 for both PGH2 and PGI2. The mechanism of formation of ions derived from collisional activation of LTA4 was studied using stable isotope labeled and chemical analogs of LTA4 and found to involve formation of highly conjugated anions at m/z 261 and 163. The collisional activation of the molecular anion of PGH2 yielded a product ion spectrum identical to that observed for the isomeric prostaglandins PGE2 and PGD2. However, it was possible to baseline separate PGE2, PDG2, and PGH2 by reversed phase HPLC using basic HPLC mobile phases. The collisional activation of PGI2 led to a family of abundant ions including highly conjugated carbon-centered and oxygen-centered radical species (m/z 245 and 205) likely derived from the attack of the carboxylate anion on the cyclic enolether of PGI2 as well as the most abundant product ion (m/z 215) which formed following loss of neutral hexanal and water. The structures of these product ions were consistent with high resolution measurements measured in a quadrupole time-of-flight mass spectrometer.     

Liquid chromatography with electrospray ion-trap mass spectrometry for the determination of anatoxins in cyanobacteria and drinking water

Anatoxin-a (AN) and homoanatoxin-a (HMAN) are potent neurotoxins produced by a number of cyanobacterial species. A new, sensitive liquid chromatography/multiple tandem mass spectrometry (LC/MS(n)) method has been developed for the determination of these neurotoxins. The LC system was coupled, via an electrospray ionisation (ESI) source, to an ion-trap mass spectrometer in positive ion mode. The [M+H](+) ions at m/z 166 (anatoxin-a) and m/z 180 (homoanatoxin-a) were used as the precursor ions for multiple MS experiments. MS(2)bond;MS(4) spectra displayed major fragment ions at m/z 149 (AN), 163 (HMAN), assigned to [Mbond;NH(3)+H](+); m/z 131 (AN), 145 (HMAN), assigned to [Mbond;NH(3)bond;H(2)O+H](+), and m/z 91 [C(7)H(7)](+). Although the chromatographic separation of these neurotoxins is problematic, reversed-phase LC, using a C(18) Luna column, proved successful. Calibration data for anatoxin-a using spiked water samples (10 mL) in LC/MS(n) modes were: LC/MS (25-1000 microg/L), r(2) = 0.998; LC/MS(2) (5-1000(microg/L), r(2) = 0.9993; LC/MS(3) (2.5-1000 microg/L), r(2) = 0.9997. Reproducibility data (% RSD, N = 3) for each LC/MS(n) mode ranged between 2.0 at 500 microg/L and 7.0 at 10 microg/L. The detection limit (S/N = 3) for AN was better than 0.03 ng (on-column) for LC/MS(3) which corresponded to 0.6 microg/L.     

Studies on azaspiracid biotoxins. II. Mass spectral behavior and structural elucidation of azaspiracid analogs

In this report, the mass spectral analysis of azaspiracid biotoxins is described. Specifically, the collision-induced dissociation (CID) behavior and differences between CID spectra obtained on a triple-quadrupole, a quadrupole time-of-flight, and an ion-trap mass spectrometer are addressed here. The CID spectra obtained on the triple-quadrupole mass spectrometer allowed the classification of the major product ions of the five investigated compounds (AZA 1-5) into five distinct fragment ion groups, according to the backbone cleavage positions. Although the identification of unknown azaspiracids was difficult based on CID alone, the spectra provided sufficient structural information to allow confirmation of known azaspiracids in marine samples. Furthermore, we were able to detect two new azaspiracid analogs (AZA 1b and 6) in our samples and provide a preliminary structural analysis. The proposed dissociation pathways under tandem mass spectrometry (MS/MS) conditions were confirmed by a comparison with accurate mass data from electrospray quadrupole time-of-flight MS/MS experiments. Regular sequential MS(n) analysis on an ion-trap mass spectrometer was more restricted in comparison to the triple-quadrupole mass spectrometer, because the azaspiracids underwent multiple [M + H - nH(2)O](+) (n = 1-6) losses from the precursor ion under CID. Thus, the structural information obtained from MS(n) experiments was somewhat limited. To overcome this limitation, we developed a wide-range excitation technique using a 180-u window that provided results comparable to the triple-quadrupole instrument. To demonstrate the potential of the method, we applied it to the analysis of degraded azaspiracids from mussel tissue extracts.     

Key fragments for identification of positional isomer pair in glucuronides from the hydroxylated metabolites of RT-3003 (Vintoperol) by liquid chromatography/electrospray ionization mass spectrometry.

The mass spectral properties of glucuronides of the 9- and 10-hydroxylated metabolites of RT-3003 (Vintoperol; (-)-1beta-ethyl-1alpha-hydroxymethyl-1,2,3,4,6,7, 12balpha-octahydroindolo[2,3-a]quinolizine), which were fractionated by high-performance liquid chromatography with fluorescence detection, were investigated using the positive ion electrospray ionization mode. These glucuronides showed predominantly the protonated molecular ion ([M + H](+) ion), and the [M + H](+) ion provided a characteristic product ion spectrum in which abundant ions were obtained at m/z 301, 160 and 142. The first ion, corresponding to the [aglycone + H](+) ion, was produced by neutral loss of the glucuronic acid moiety from the [M + H](+) ion. The product ion spectrum of the [M + H](+) ion of hydroxy-RT-3003 revealed a number of ions common to the glucuronide spectra, suggesting that other two ions observed most likely represent fragmentation of hydroxy-RT-3003. In turn, these glucuronides were positional isomers with respect to the binding site of glucuronic acid. The structures of the isomer pairs were discriminated by the presence of the ion of m/z 318 or 336 in the product ion spectrum. These ions were produced by fission of the C-ring, the same as for the formation of the ions of m/z 160 and 142, as were observed in the product ion spectrum from the [M + H](+) ion of hydroxy-RT-3003. For the formation of these ions, an unusual fragmentation process was proposed, and these ion structures were supported by evidence from the accurate mass measurement data. Additionally, in the sulfates of hydroxylated metabolites, a similar product ion corresponding to the ion of m/z 336 found in the phenolic glucuronides was observed, and was applied for identification of the sulfate metabolites.     

Mass spectrometry for the characterization of unsulfated chondroitin oligosaccharides from 2-mers to 16-mers. Comparison with hyaluronic acid oligomers

This study reports for the first time the complete liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (MS/MS) analyses performed in negative ion mode of saturated unsulfated chondroitin oligosaccharides up to 16-mers and comparison with hyaluronic acid (HA) oligomers differing only in the nature of the hexosamine residue. MS/MS of the chondroitin disaccharide on the singly charged precursor at m/z 396.1 afforded a glycosidic cleavage C1 product ion at m/z 192.9. In the tetrasaccharide, C2 (m/z 396.0) and C3 (m/z 572.0) product anions were generated by glycosidic cleavage. A C5 [M-2H]2- product ion at m/z 475.1 was generated by the glycosidic cleavage of the hexasaccharide, and a C7 ion (m/z 664.6, charge state of -2) was produced from the octasaccharide. The same fragmentation pattern of deprotonated oligomers was observed for the largest oligosaccharides, from 10- to 16-mers. There has been no previous report of MS/MS spectra for unsulfated chondroitin oligomers of these sizes. Unsulfated saturated chondroitin oligosaccharides with x-mer units and larger than a tetrasaccharide dissociate to almost exclusively form CX-1-type ions. Saturated HA oligomers also afforded the same fragmentation pattern as deprotonated oligomers by ESI-MS and MS/MS analyses. Thus, under the experimental conditions used in the current study, we were unable to distinguish between unsulfated chondroitin and HA.     

A novel precursor ion discovery method on a hybrid quadrupole orthogonal acceleration time-of-flight (Q-TOF) mass spectrometer for studying protein phosphorylation

A tandem quadrupole time-of-flight (Q-TOF) mass spectrometer has been programmed such that phosphorylated peptides can automatically be discovered and identified in a way similar to that of the use of precursor ion or neutral loss scanning, but without the need to scan the quadrupole mass filter. Instead, the method capitalizes on the innate capability of the Q-TOF to record mass spectra and product ion spectra quickly, with good sensitivity and with good mass accuracy. Alternate mass spectra, with and without fragmentation, are recorded at high and low collision energy with the quadrupole operating in wideband mode. The method of analysis is both compatible with and dependant on liquid chromatography for separation of complex mixtures. The method has been demonstrated by searching for the neutral loss of 98 Da (H3PO4) from phosphoserine and phosphothreonine residues, or for the phosphorylated immonium ion at m/z 216 from phosphotyrosine. The method also incorporates acquisition of the product ion spectrum from any candidate precursor ions, thereby allowing confirmation of the neutral loss or product ion and providing additional sequence information to assist identification of the protein and assign the site of phosphorylation.     

Analysis of triacetone triperoxide (TATP) and TATP synthetic intermediates by electrospray ionization mass spectrometry

The explosive triacetone triperoxide (TATP) has been analyzed by electrospray ionization mass spectrometry (ESI-MS) on a linear quadrupole instrument, giving a 62.5 ng limit of detection in full scan positive ion mode. In the ESI interface with no applied fragmentor voltage the m/z 245 [TATP + Na](+) ion was observed along with m/z 215 [TATP + Na - C(2)H(6)](+) and 81 [(CH(3))(2)CO + Na](+). When TATP was ionized by ESI with an applied fragmentor voltage of 75 V, ions at m/z 141 [C(4)H(6)O(4) + Na](+) and 172 [C(5)H(9)O(5) + Na](+) were also observed. When the precipitates formed in the synthesis of TATP were analyzed before the reaction was complete, a new series of ions was observed in which the ions were separated by 74 m/z units, with ions occurring at m/z 205, 279, 353, 427, 501, 575, 649 and 723. The series of evenly spaced ions is accounted for as oligomeric acetone carbonyl oxides terminated as hydroperoxides, [HOOC(CH(3))(2){OOC(CH(3))(2)}(n)OOH + Na](+) (n = 1, 2 ... 8). The ESI-MS spectra for this homologous series of oligoperoxides have previously been observed from the ozonolysis of tetramethylethylene at low temperatures. Precipitates from the incomplete reaction mixture, under an applied fragmentor voltage of 100 V in ESI, produced an additional ion observed at m/z 99 [C(2)H(4)O(3) + Na](+), and a set of ions separated by 74 m/z units occurring at m/z 173, 247, 321, 395, 469 and 543, proposed to correspond to [CH(3)CO{OOC(CH(3))(2)}(n)OOH + Na](+) (n = 1,2 ... 5). Support for the assigned structures was obtained through the analysis of both protiated and perdeuterated TATP samples.     

The distinction of underivatized monosaccharides using electrospray ionization ion trap mass spectrometry

A convenient method for distinguishing underivatized isomeric monosaccharides has been established using electrospray ionization ion trap mass spectrometry (ESI-ITMS). Mass spectra of hexoses (glucose, galactose, and mannose), N-acetylhexosamines (N-acetylglucosamine, N-acetylgalactosamine, and N-acetylmannosamine) and hexosamines (glucosamine, galactosamine, and mannosamine) dissolved in solvent containing 1 mM ammonium acetate were obtained in the positive ion mode. Glucose was distinguished from galactose and mannose in the MS(2) spectrum of the [M+NH(4)](+) ion at m/z 198. The MS(3) spectra generated from [M+NH(4)-H(2)O-NH(3)](+) at m/z 163 showed that galactose and mannose could be distinguished by the ratio of peak intensities at m/z 145 and 127, while the three N-acetylhexosamine and hexosamine stereochemical isomers could be identified by the relative abundance ratios of product ions observed in MS(3) spectra. The investigation of MS and MS(2) spectra from complexes of these monosaccharides with Na(+) and Pb(2+) failed to distinguish these monosaccharide isomers. Therefore, multiple stage mass analysis by ESI-ITMS using either [M+NH(4)](+) or [M+H](+) was useful to distinguish between the isomers of monosaccharides.     

The diphosphate monoanion in the gas phase: a joint mass spectrometric and theoretical study

H(3)P(2)O(7) (-) ions were obtained in an electrospray ion source of a Fourier transform ion cyclotron resonance (ESI/FTICR) mass spectrometer from a CH(3)CN/H(2)O (1:1) pyrophosphoric acid solution and in the ionic source of a triple quadrupole (TQ) mass spectrometer from the chemical ionisation (CI) of pyrophosphoric acid introduced by a thermostatically controlled direct insertion probe. The ions were structurally characterised by mass spectrometric techniques and theoretical calculations. Consistent with collisionally activated dissociation (CAD) mass spectrometric results, theoretical calculations identified the linear diphosphate anion (I) as the most stable isomer on the H(3)P(2)O(7) (-) potential energy surface. The joint application of mass spectrometric techniques and theoretical methods provided information on the dissociative processes of diphosphate anions in the gas phase. Finally, this study provides an insight into the structures and stabilities of the [H(3)PO(4).PO(3)](-), [HP(2)O(6).H(2)O](-) and [H(2)PO(4).HPO(3)](-) clusters and allows the stability and structure of the dimetaphosphate anion, HP(2)O(6) (-), to be investigated at the B3LYP6-31+G* and CCSD(T) levels of theory.     

Structural determination of the novel fragmentation routes of zwitteronic morphine opiate antagonists naloxonazine and naloxone hydrochlorides using electrospray ionization tandem mass spectrometry

Electrospray ionization quadrupole time-of-flight (ESI-QqToF) mass spectra of the zwitteronic salts naloxonazine dihydrochloride 1 and naloxone hydrochloride 2, a common series of morphine opiate receptor antagonists, were recorded using different declustering potentials. The singly charged ion [M+H-2HCl](+) at m/z 651.3170 and the doubly charged ion [M+2H-2HCl](2+) at m/z 326.1700 were noted for naloxonazine dihydrochloride 1; and the singly charged ion [M+H-HCl](+) at m/z 328.1541 was observed for naloxone hydrochloride 2. Low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) experiments established the fragmentation routes of these compounds. In addition to the characteristic diagnostic product ions obtained, we noticed the formation of a series of radical product ions for the zwitteronic compounds 1 and 2, and also the formation of a distonic ion product formed from the singly charged ion [M+H-HCl](+) of naloxone hydrochloride 2. Confirmation of the various established fragmentation routes was effected by conducting a series of ESI-CID-QqTof-MS/MS product ion scans, which were initiated by CID in the atmospheric pressure/vacuum interface using a higher declustering potential. Deuterium labeling was also performed on the zwitteronic salts 1 and 2, in which the hydrogen atoms of the OH and NH groups were exchanged with deuterium atoms. Low-energy CID-QqTof-MS/MS product ion scans of the singly charged and doubly charged deuteriated molecules confirmed the initial fragmentation patterns proposed for the protonated molecules. Precursor ion scan analyses were also performed with a conventional quadrupole-hexapole-quadrupole tandem mass spectrometer and allowed the confirmation of the genesis of some diagnostic ions.