Ion Electrospray Ionization Mass Spectrometry Research Articles

Tetramethylammonium Hydroxide as a Reagent for Complex Mixture Analysis by Negative Ion Electrospray Ionization Mass Spectrometry

Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) enables the direct characterization of complex mixtures without prior fractionation. High mass resolution can distinguish peaks separated by as little as 1.1 mDa), and high mass accuracy enables assignment of elemental compositions in mixtures that contain tens of thousands of individual components (crude oil). Negative electrospray ionization (ESI) is particularly useful for the speciation of the most acidic petroleum components that are implicated in oil production and processing problems. Here, we replace conventional ammonium hydroxide by tetramethylammonium hydroxide (TMAH, a much stronger base, with higher solubility in toluene) to more uniformly deprotonate acidic components of complex mixtures by negative ESI FTICR MS. The detailed compositional analysis of four crude oils (light to heavy, from different geographical locations) reveals that TMAH reagent accesses 1.5-6 times as many elemental compositions, spanning a much wider range of chemical classes than does NH4OH. For example, TMAH reagent produces abundant negative electrosprayed ions from less acidic and neutral species that are in low abundance or absent with NH4OH reagent. More importantly, the increased compositional coverage of TMAH-modified solvent systems maintains, or even surpasses, the compositional information for the most acidic species. The method is not limited to petroleum-derived materials and could be applied to the analysis of dissolved organic matter, coal, lipids, and other naturally occurring compositionally complex organic mixtures.

Monitoring Haloperidol Exposure in Body Fluids and Hair of Children by Liquid Chromatography–High-Resolution Mass Spectrometry

Haloperidol, 4-[4-(4-chlorophenyl)-4-hydroxy-1-piperidinyl]-1-(4-fluorophenyl)-1-butanone (HP), one of the most widely used antipsychotics in the treatment of schizophrenia, mania, and other psychiatric disorders, is frequently encountered in cases of unintentional pediatric intoxication because the ingestion of a small amount can cause significant toxic effects in children. For monitoring HP in suspected ingestions, a liquid chromatography-high-resolution mass spectrometry method has been developed and validated in urine, blood, and hair samples. The analyte was extracted from 1 mL blood or urine by liquid/liquid extraction and from 5 mg of hair by micropulverized extraction; gradient elution on an Atlantis T3 column was realized using HP-d4 as an internal standard. Positive ion electrospray ionization and high-resolution mass spectrometry determination were performed in an Orbitrap mass spectrometer. The method exhibited a r > 0.999 in the studied ranges (0.1-50 ng/mL in urine and blood and 0.1-50 ng/mg in hair) and a limit of quantification of 0.1 ng/mL for urine and blood and 0.1 ng/mg for hair; intra-assay and interassay relative SDs were always more than 18%. The method was applied to determine haloperidol in 3 children who were admitted to emergency departments. HP concentrations ranged from 2 to 21 ng/mL in urine, from not detected to 4.9 ng/mL in blood, and from 0.37 to 0.73 ng/mg in hair samples. The utilization of high-resolution/high-accuracy mass spectrometry in full scan mode allowed the identification of HP metabolites in urine and blood, thus unequivocally documenting the exposure to the drug. HP metabolites were structurally characterized by high-resolution multiple mass spectrometry. For the first time, a HP metabolite was detected in hair.

The relationship between electrospray ionization behavior and cytotoxic activity of [MI(P)4]+‐type complexes (M = Cu, Ag and Au; P = tertiary phosphine)

To try to find a correlation between the antiproliferative activity of a series of [M(I)(P)4](+) complexes (M = Cu, Ag and Au; P = tertiary phosphine) and their stability at micromolar concentration under mass spectrometric conditions. [M(I)(P)4](+) complexes were investigated by positive ion electrospray ionization mass spectrometry with multiple collisional experiments using an ion trap mass spectrometer. The displacement of P from native [M(I)(P)4](+), previously described for the copper derivative, is common for the triad complexes leading to the formation of [M(P)3](+) and [M(P)2](+) adducts. Further dissociation of [M(P)2](+) depends on the nature of the metal (Cu ~ Ag > Au). More labile [Cu(P)2](+) and [Ag(P)2](+) are more cytotoxic against HCT-15 human colon carcinoma cells compared to less labile [Au(P)2](+) species. The dissociation of P ligand(s) from the [M(I)(P)4](+) complexes is the driving force for the triggering of the antiproliferative activity. The more favored is the displacement of P from the [M(P)2](+) active form, the more favored is in turn the possibility for the metal to interact with biological substrates related to cancer proliferation.

High-performance liquid chromatography with paired ion electrospray ionization (PIESI) tandem mass spectrometry for the highly sensitive determination of acidic pesticides in water

A novel method based on the paired ion electrospray ionization (PIESI) mass spectrometry has been developed for determination of acidic pesticides at ultratrace levels in surface and ground waters. The proposed approach provides greatly enhanced sensitivity for acidic pesticides and overcomes the drawbacks of the less sensitive negative ion mode ESI-MS. The limits of detection (LODs) of 19 acidic pesticides were evaluated with four types of dicationic ion-pairing reagent (IPR) in both single ion monitoring (SIM) and selected reaction monitoring (SRM) mode. The LOD of 19 pesticides obtained with the use the optimal dicationic ion-pairing reagent ranged from 0.6pg to 19pg, indicating the superior sensitivity provided by this method. The transition pathways for different pesticide-IPR complexes during the collision induced dissociation (CID) were identified. To evaluate and eliminate any matrix effects and further decrease the detection limits, off-line solid-phase extraction (SPE) was performed for DI water and a river water matrix spiked with 2000ngL−1 and 20ngL−1 pesticides standards respectively, which showed an average percent recovery of 93%. The chromatographic separation of the acidic pesticides was conducted by high-performance liquid chromatography (HPLC) using a C18 column (250mm×2.1mm) in the reversed phase mode using linear gradient elution. The optimized HPLC–PIESI-MS/MS method was utilized for determination of acidic pesticide at ngL−1 level in stream/pond water samples. This experimental approach is 1–3 orders of magnitude more sensitive for these analytes than other reported methods performed in the negative ion mode.

Solution species of Fe(iii), Ga(iii), In(iii) or Ln(iii) and suberodihydroxamic acid from electrospray ionization mass spectrometry

Positive ion electrospray ionization mass spectrometry (ESI-MS) was used to characterize complexes formed in aqueous solution between Fe(III), Ga(III), In(III), Ce(III), Eu(III) or Yb(III), and the linear dihydroxamic acid suberodihydroxamic acid (HONHC(O)(CH2)nC(O)NHOH), n = 6; L6H4) at pH 2.5, and at metal (M) to ligand (L) ratios of 1 : 1 or 1 : 2. In the Ga(III)–L6H4 system, complexes with five different types of M : L stoichiometries were identified, with the major signals assigned to [Ga(L6H2)·CH3OH]+ (M : L, 1 : 1), [Ga(L6H2)(L6H3)] adducts (H+, Na+, K+) (M : L, 1 : 2), [Ga2(L6H2)2(μ-OCH3)]+ (M : L, 2 : 2), [Ga2(L6H2)3] adducts (H+, Na+, K+) (M : L, 2 : 3), or [Ga3(L6H2)4]+ (M : L, 3 : 4). Where M = Ce(III), Eu(III) or Yb(III), signals for [M(L6H2)(L6H3)] (H+ adduct) were dominant, signals for [M3(L6H2)4]+ were weak, and signals for [M2(L6H2)2(μ-OCH3)]+ were either weak (Ce(III)) or absent (Eu(III), Yb(III)), which reflected that the higher coordination number demands of lanthanide ions were not satisfied by the latter two stoichiometry types. An improved understanding of the solution speciation between different types of metal ions and hydroxamic acids is important in the context of the roles played by these ligands in bioremediation/biogeochemistry and biomedicine/imaging.

Mass Spectrometry of the Lithium Adducts of Diacylglycerols Containing Hydroxy FA in Castor Oil and Two Normal FA

AbstractCastor oil can be used in industry. The molecular species of triacylglycerols containing hydroxy fatty acids (FA) in castor oil have been identified. We report here the identification of twelve diacylglycerols (DAG) containing hydroxy FA in castor oil using positive ion electrospray ionization mass spectrometry of the lithium adducts. They were RR (diricinolein, R is ricinoleate), RL, RS, R‐diOH18:0, R‐diOH18:1, R‐diOH18:2, R‐triOH18:0, R‐triOH18:1, R‐triOH18:2, diOH18:0‐diOH18:1, diOH18:1‐diOH18:1 and diOH18:1‐diOH18:2. The MS2 fragment ions, [M + Li − FA]+ and [FA + Li]+, from the lithium adducts of DAG containing hydroxy FA (one or two hydroxy FA), were used for the identification. The additional fragment ions from the neutral losses of FA lithium salts [M + Li − FALi]+ were used for the identification of eleven DAG containing two normal FA in a soybean oil bioconversion product. The MS2 fragment ions from the neutral losses of FA lithium salts [M + Li − FALi]+ were not detected from the DAG containing hydroxy FA. The DAG containing FA with more hydroxyl groups than the other FA on the same DAG molecule tended to have a prominent fragment ion [FA + Li]+ and an undetectable fragment ion [M + Li − FA]+ while the FA was the more hydroxylated FA. Also the less hydroxylated FA of a DAG tended to have a prominent fragment ion [M + Li − FA]+ and an undetectable fragment ion [FA + Li]+ while the FA was the less hydroxylated FA.

Mass spectra of halogenostyrylbenzoxazoles

Several series of styrylbenzoxazoles of general formula XC6H3(NCO)CHCHC6H4Y [X=F, Cl or Br; Y=H, F, Cl, Br, CH3 or CH3O] have been investigated by positive ion electrospray and electron ionization mass spectrometry. These compounds, many of which are biologically active or have pharmaceutical potential, show in their electrospray spectra strong peaks for MH+ ions, which undergo relatively little fragmentation. The electron ionization spectra are extremely clean, being dominated by the loss of an atom or radical, Y, from the ortho position of the pendant ring, by a rearrangement that may be interpreted as a proximity effect. The resultant [M−Y]+ ions are exceptionally stable and rarely undergo further fragmentation. The analytical value of this proximity effect, which is analogous to intramolecular aromatic substitution, in revealing the presence of a substituent in the pendant ring and determining its position, is emphasized. Elimination of a species (including H or F) derived from an ortho substituent in the pendant ring occurs even when apparently more favourable alternative fragmentation is possible by direct cleavage of the CX bond (X=Cl or Br) in the benzoxazole ring.

Separation and identification of smokeless gunpowder additives by capillary electrochromatography

This paper details a method for the separation and identification of fourteen organic compounds commonly found as constituents in commercial smokeless powders using a hexyl acrylate-based porous monolith. Capillary electrochromatography (CEC) coupled to UV and time of flight-mass spectrometry (TOF-MS) methods were both explored. The CEC–UV method provides an effective and efficient method for the detection of all components in the additive package of the powder. The TOF-MS procedure provides better sensitivity and selectivity allowing an additional confirmation of the presence of the subset of those compounds, which are detectable via positive and/or negative ion electrospray ionization mass spectrometry. Both methods were used for the analysis of smokeless powder components in a mixed standard as well as in the determination of the composition of the additive package of individual powders.

Development and validation of liquid chromatography–mass spectrometric method for simultaneous determination of moxifloxacin and ketorolac in rat plasma: application to pharmacokinetic study

A highly sensitive, selective and rapid liquid chromatography-electrospray ionization mass spectrometry (LC-MS) method has been developed and validated for simultaneous determination of moxifloxacin (MFX) and ketorolac (KTC) in rat plasma. Gemifloxacin (GFX) was used as an internal standard (IS). A simple protein precipitation method was used for the extraction of analytes from rat plasma. Effective chromatographic separation of MFX, KTC and GFX was achieved on a Kromasil C(18) column (100 × 4.6 mm, 5 µm) using a mobile phase consisting of acetonitrile-10 mm ammonium acetate (pH 2.5)-0.1% formic acid (50:25:25) in an isocratic elution, followed by detection with positive ion electrospray ionization mass spectrometry using target ions of [M + H](+) at m/z 402 for MFX, m/z 256 for KTC and m/z 390 for GFX in selective ion recording mode. The method was validated over the calibration range of 5-100 ng/mL for MFX and 10-6000 ng/mL for KTC. The method demonstrated good performances in terms of intra- and inter-day precision (0.97-5.33%) and accuracy (93.91-101.58%) for both MFX and KTC, including lower and upper limits of quantification. The recoveries from spiked control samples were >75% for MFX and >79% for KTC. The matrix effect was found to be negligible and the stability data were within acceptable limits. Further, the method was also successfully applied to a single-dose pharmacokinetic study in rats. This method can be extended to measure plasma concentrations of both drugs in human to understand drug interaction and adverse effects.

Plasma pencil atmospheric mass spectrometry detection of positive ions from micronutrients emitted from surfaces.

Analysis and detection of micronutrients is important for the reduction of the global burden of malnutrition-related disease. A relatively new technique, plasma pencil atmospheric mass spectrometry (PPAMS) was applied in a comprehensive evaluation for rapid, simultaneous detection of the key micronutrients zinc, iron, folate, vitamin A, and iodine. PPAMS was performed through the coupling of a low-temperature plasma pencil to an atmospheric mass spectrometer. The effectiveness of the PPAMS system was demonstrated through the generation of characteristic mass spectra and tandem mass spectra on neat micronutrient powders suspended on double-sided tape. The analytical performance and ability to qualitatively separate out the nutrients from a complex biological solution and each other was then assessed through the application of PPAMS on a sample matrix of micronutrients in porcine plasma in which nutrient concentration is varied from high blood level concentrations (HBLCs) to low blood level concentrations (LBLCs). A multivariate analysis method, principal component analysis (PCA), was then used to qualitatively separate the fragments obtained by nutrient type. The resulting plots of PCA scores of the positive-ion spectra from each mixed sample showed excellent separation of HBLCs and LBLCs of single nutrients at the 95% confidence level (Wagner et al. Langmuir 2001, 17, 4649-4660). The associated plots of PCA loadings showed that key loadings could be attributed to the expected micronutrient fragments. The PPAMS technique was successfully demonstrated and compared with traditional MS techniques: time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electrospray ionization mass spectrometry (ESI-MS). Separation of the nutrients at concentrations relevant for human blood-based nutrient detection was possible by both ESI-MS and PPAMS. However, only PPAMS could detect the nutrients at physiological concentrations from porcine plasma. ToF-SIMS could detect the nutrients from plasma solution but required 5 to 1000-times higher concentrations of folate, vitamin A, and iodine to achieve adequate separation of the micronutrients by PCA.

Chemical characterisation of humic-like substances from urban, rural and tropical biomass burning environments using liquid chromatography with UV/vis photodiode array detection and electrospray ionisation mass spectrometry

Environmental contextOne of the most important classes of water-soluble organic compounds in continental fine and tropical biomass burning aerosol is humic-like substances (HULIS), which contain components with strong polar, acidic and chromophoric properties. We focus on the chemical characterisation of HULIS and provide evidence that nitro-aromatic catecholic compounds are among the major species of HULIS. This indicates that volatile aromatic hydrocarbons emitted during biomass burning are important gas-phase precursors for HULIS. AbstractHumic-like substances (HULIS) are ubiquitously present in the troposphere and make up a major fraction of continental fine-sized water-soluble organic compounds. They are regarded as material with strong polar, acidic and chromophoric properties; however, structural information at the individual component level is rather limited. In the present study, we have characterised HULIS from different locations using liquid chromatography coupled to photodiode array detection and negative ion electrospray ionisation mass spectrometry. Aerosol samples with particles less than 2.5 μm in diameter (PM2.5) were collected in Budapest and K-puszta, Hungary, during 2007 and 2008 spring and summer periods, and in Rondônia, Brazil, during a 2002 biomass burning experiment. Major components of the Budapest 2007 and Brazil 2002 HULIS corresponded to chromophoric substances, of which 4-nitrocatechol (molecular weight (MW) 155) was identified as the most abundant organic species and less abundant ones were attributed to mono- and dimethyl nitrocatechols (MWs 169 and 183). The mass concentrations of 4-nitrocatechol in the water-soluble organic carbon (WSOC) of the Budapest 2007 and day- and night-time Brazil 2002 HULIS were 0.46, 0.50 and 1.80 %. Abundant components of K-puszta 2008 HULIS were assigned to α-pinene secondary organic aerosol (SOA) tracers, i.e. 3-methyl-1,2,3-butanetricarboxylic acid and terpenylic acid; their mass concentrations in the HULIS WSOC were 0.75 and 0.40 %. Tere- and ortho-phthalic acids (MW 166) were major components of the Budapest and K-puszta HULIS, but only minor ones of the Brazil 2002 biomass burning HULIS, consistent with a source that is different from biomass burning and likely related to open waste burning of phthalate ester-containing material such as plastic.

Rapid and specific detection of urea nitrate and ammonium nitrate by electrospray ionization time‐of‐flight mass spectrometry using infusion with crown ethers

Urea nitrate (UN) and ammonium nitrate (AN) are fertilizer-based explosives that are commonly used in improvised munitions and can have highly destructive effects. Because they are in the form of salts, their relatively low volatility makes them difficult to detect at trace levels. In addition, these salts readily undergo metathetic reactions in water to form urea, ammonium and nitrate, which are ubiquitous in the environment. Thus, selective methods are needed for their detection. In this study, a procedure was developed to detect UN and AN in non-aqueous environments by positive ion electrospray ionization mass spectrometry through the addition of 18-crown-6. The method is sensitive, with detection limits under 2 μM, and selective. The procedure is capable of differentiating urea from uronium ions (protonated urea) and a mixture of urea and AN did not interfere with the UN signal. The procedure is quite versatile and the addition of crown ethers to the sample matrix does not interfere with the detection of high explosives in the negative ionization mode. Experimental results are presented on the utilization of the method in the detection of UN and AN on various surfaces. Semi-quantitative studies showed that AN and UN can be detected at trace levels following finger transfer and a series of studies were performed to demonstrate the effect of various interferences. The results show the method to be a quick and robust procedure for trace detection.

Development and validation of an enantioselective liquid-chromatography/tandem mass spectrometry method for the separation and quantification of eslicarbazepine acetate, eslicarbazepine, R-licarbazepine and oxcarbazepine in human plasma

The purpose of this study was develop and validate a sensitive and specific enantioselective liquid–chromatography/tandem mass spectrometry (LC–MS/MS) method, for the simultaneous quantification of eslicarbazepine acetate (ESL), eslicarbazepine (S-Lic), oxcarbazepine (OXC) and R-licarbazepine (R-Lic) in human plasma. Analytes were extracted from human plasma using solid phase extraction and the chromatographic separation was achieved using a mobile phase of 80% n-hexane and 20% ethanol/isopropyl alcohol (66.7/33.3, v/v). A Daicel CHIRALCEL ® OD-H column (5 μm, 50 mm × 4.6 mm) was used with a flow rate of 0.8 mL/min, and a run time of 8 min. ESL, S-Lic, R-Lic, OXC and the internal standard, 10,11-dihydrocarbamazepine, were quantified by positive ion electrospray ionization mass spectrometry. The method was fully validated, demonstrating acceptable accuracy, precision, linearity, and specificity in accordance with FDA regulations for the validation of bioanalytical methods. Linearity was proven over the range of 50.0–1000.0 ng/mL for ESL and OXC and over the range of 50.0–25,000.0 ng/mL for S-Lic and R-Lic. The intra- and inter-day coefficient of variation in plasma was less than 9.7% for ESL, 6.0% for OXC, 7.7% for S-Lic and less than 12.6% for R-Lic. The accuracy was between 98.7% and 107.2% for all the compounds quantified. The lower limit of quantification (LLOQ) was 50.0 ng/mL for ESL, S-Lic, OXC and R-Lic in human plasma. The short-term stability in plasma, freeze–thaw stability in plasma, frozen long-term stability in plasma, autosampler stability and stock solution stability all met acceptance criteria. The human plasma samples, collected from 8 volunteers, showed that this method can be used for therapeutic monitoring of ESL and its metabolites in humans treated with ESL.

Analysis of oligonucleotides by hydrophilic interaction liquid chromatography coupled to negative ion electrospray ionization mass spectrometry

Hydrophilic interaction liquid chromatography (HILIC) is here successfully coupled to negative-ion electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) for the analysis of synthetic and chemically modified oligonucleotides. Separation was performed on a 2.1 mm × 100 mm PEEK ZIC ® HILIC column packed with hydrophilic stationary phase with a permanent zwitterionic functional group and a particle size of 3.5 μm with an average pore diameter of 200 Å. A method was developed to separate homogeneous and heterogeneous oligonucleotides as well as methylated oligonucleotides using a quaternary pumping system containing ammonium acetate and water with an acetonitrile gradient. Analyses of oligonucleotides were performed by LC/MS with a detection limit of 2.5 picomole (20 mer) with signal to noise ratio (S/N) of 4.12. The influence of the eluent composition, type of buffer and its concentration, and organic modifier were also evaluated. The HILIC LC/MS method presented in this paper used common, ‘MS friendly’, mobile phases achieving sensitive and selective oligonucleotide analysis.

Complexes formed in solution between vanadium(IV)/(V) and the cyclic dihydroxamic acid putrebactin or linear suberodihydroxamic acid.

An aerobic solution prepared from V(IV) and the cyclic dihydroxamic acid putrebactin (pbH2) in 1:1 H2O/CH3OH at pH = 2 turned from blue to orange and gave a signal in the positive ion electrospray ionization mass spectrometry (ESI-MS) at m/zobs 437.0 attributed to the monooxoV(V) species [VVO(pb)]+ ([C16H26N4O7V]+, m/zcalc 437.3). A solution prepared as above gave a signal in the 51V NMR spectrum at δV = −443.3 ppm (VOCl3, δV = 0 ppm) and was electron paramagnetic resonance silent, consistent with the presence of [VVO(pb)]+. The formation of [VVO(pb)]+ was invariant of [V(IV)]:[pbH2] and of pH values over pH = 2–7. In contrast, an aerobic solution prepared from V(IV) and the linear dihydroxamic acid suberodihydroxamic acid (sbhaH4) in 1:1 H2O/CH3OH at pH values of 2, 5, or 7 gave multiple signals in the positive and negative ion ESI-MS, which were assigned to monomeric or dimeric V(V)– or V(IV)–sbhaH4 complexes or mixed-valence V(V)/(IV)–sbhaH4 complexes. The complexity of the V-sbhaH4 system has been attributed to dimerization (2[VVO(sbhaH2)]+ ↔ [(VVO)2(sbhaH2)2]2+), deprotonation ([VVO(sbhaH2)]+ – H+ ↔ [VVO(sbhaH)]0), and oxidation ([VIVO(sbhaH2)]0 –e– ↔ [VVO(sbhaH2)]+) phenomena and could be described as the sum of two pH-dependent vectors, the first comprising the deprotonation of hydroxamate (low pH) to hydroximate (high pH) and the second comprising the oxidation of V(IV) (low pH) to V(V) (high pH). Macrocyclic pbH2 was preorganized to form [VVO(pb)]+, which would provide an entropy-based increase in its thermodynamic stability compared to V(V)–sbhaH4 complexes. The half-wave potentials from solutions of [V(IV)]:[pbH2] (1:1) or [V(IV)]:[sbhaH4] (1:2) at pH = 2 were E1/2 −335 or −352 mV, respectively, which differed from the expected trend (E1/2 [VO(pb)]+/0 < VV/IV–sbhaH4). The complex solution speciation of the V(V)/(IV)–sbhaH4 system prevented the determination of half-wave potentials for single species. The characterization of [VVO(pb)]+ expands the small family of documented V–siderophore complexes relevant to understanding V transport and assimilation in the biosphere.

Characterization and Purification of Commercial SPS and MPS by Ion Chromatography and Mass Spectrometry

SPS (bis-(3-sulfopropyl) disulfide) is an essential electrolyte additive used in the fabrication of copper interconnects by electrodeposition. In electroplating baths, the disulfide component of SPS may be cleaved to form the thiol analog, MPS (3-mercaptopropyl sulfonate), by either homogenous interactions with the Cu(I) reaction intermediate or by dissociative adsorption onto the copper surface. However, mechanistic studies into the role of these additives in copper electrodeposition are presently constrained by limited knowledge of the purity of commercially available SPS and MPS. This report details the use of ion chromatography (IC) and electrospray ionization mass spectrometry to characterize aqueous solutions of commercial SPS and MPS source materials. Sulfate (2.0%) and propane disulfonic acid (0.9%) (PDS) were determined to be the principal impurities in SPS (96.3% estimated purity, mass fraction). IC fractionation was used to purify and isolate SPS for surface and electroanalytical studies. Stability of SPS, MPS, and PDS in the presence of and Cu(II) was also examined. No degradation of SPS or PDS in aqueous solution was observed over a period. Solutions of MPS were metastable to saturation, but the addition of Cu(II) resulted in formation of SPS by dimerization as well as parasitic PDS generation.

Mass spectral analysis of N‐oxides of Chemical Weapons Convention related aminoethanols under electrospray ionization conditions

N,N'-Dialkylaminoethanols are the hydrolyzed products or precursors of chemical warfare agents such as V-agents and nitrogen mustards, and they are prone to undergo oxidation in environmental matrices or during decontamination processes. Consequently, screening of the oxidized products of aminoethanols in aqueous samples is an important task in the verification of chemical weapons convention-related chemicals. Here we report the successful characterization of the N-oxides of N,N'-dialkylaminoethanols, alkyl diethanolamines, and triethanolamine using positive ion electrospray ionization mass spectrometry. The collision-induced dissociation (CID) spectra of the [M+H](+) and [M+Na](+) ions show diagnostic product ions that enable the unambiguous identification of the studied N-oxides, including those of isomeric compounds. The proposed fragmentation pathways are supported by high-resolution mass spectrometry data and product/precursor ion spectra. The CID spectra of [M+H](+) ions included [MH-CH(4)O(2)](+) as the key product ion, in addition to a distinctive alkene loss that allowed us to recognize the alkyl group attached to the nitrogen. The [M+Na](+) ions show characteristic product ions due to the loss of groups (R) attached to nitrogen either as a radical (R) or as a molecule [R+H or (R-H)] after hydrogen migration.

Fragmentation patterns of novel dithiocarbamate derivatives with pharmaceutical activity under electrospray ionization tandem mass spectrometry conditions

The fragmentation patterns of a novel series of dithiocarbamate derivatives with pharmaceutical activity were investigated by positive ion electrospray ionization mass spectrometry in conjunction with tandem mass spectrometry (ESI-MS(n)). In the gas phase, the dithiocarbamate protonated molecules containing the piperazinium moiety undergo losses of bromide to form the piperazinium cation by ionization, followed by subsequent losses of methyl bromide, ring opening and rearrangement of piperazinium. Furthermore, the dithiocarbamate derivatives and their intermediates both undergo cleavage of the C-S bond to produce two common fragment ions. The different fragmentation observed for these compounds facilitated their identification and could be valuable in the further study of their metabolic pathways as prodrugs.

Determination of glyphosate and aminomethylphosphonic acid in rice using liquid chromatography-tandem mass spectrometry

A method was developed for the determination of glyphosate (GLY) and aminomethylphosphonic acid (AMPA) in rice using liquid chromatography tandem mass spectrometry (LC-MS/MS). The sample was extracted with water followed by a simple cleanup with a C18 solid phase extraction (SPE) cartridge, and then GLY and AMPA were derivatized using 9-fluorenylmethoxycarbonyl (FMOC-Cl) in borate buffer. The derivatives of GLY and AMPA were separated on a C18 column with gradient elution with the mobile phase of acetonitrile and 5 mmol/L ammonium acetate (pH 9), and finally detected with negative ion electrospray ionization-mass spectrometry (ESI-MS) in multiple reaction monitoring (MRM) mode. The results showed that the linearities of GLY and AMPA were in the concentration range of 0.000 50 to 1.0 mg/L with the correlation coefficients of 0.999 7 and 0.999 9, respectively. The mean spiked recoveries of GLY and AMPA at 3 spiked levels ranged from 72.5% to 113.6% with the relative standard deviations (RSD, n = 5) of 3.8% - 16.2%. The limits of detection were 2.0 and 3.0 microg/kg for GLY and AMPA, respectively. This method is rapid, sensitive, and suitable for simultaneous determination of GLY and AMPA in rice.

Comparative analysis of crystallins and lipids from the lens of Antarctic toothfish and cow

Animal model systems of senile cataract and lens crystallin stability are essential to understand the complex nature of lens transparency. Our aim in this study was to assess the long-lived Antarctic toothfish Dissostichus mawsoni (Norman) as a model system to understand long-term lens clarity in terms of solubility changes that occur to crystallins. We compared the toothfish with the mammalian model cow lens, dissecting each species' lens into a cortex and nuclear region. In addition to crystallin distribution, we also assayed fatty acid (FA) composition by negative ion electrospray ionization mass spectrometry (ESI-MS). The majority of toothfish lens crystallins from cortex (90.4%) were soluble, whereas only a third (31.8%) from the nucleus was soluble. Crystallin solubility analysis by SDS-PAGE and immunoblots revealed that relative proportions of crystallins in both soluble and urea-soluble fractions were similar within each species examined and in agreement with previous reports for bovine lens. From our data, we found that both toothfish and cow crystallins follow patterns of insolubility that mirror each animals lens composition with more γ crystallin aggregation seen in the toothfish lens nucleus than in cow. Toothfish lens lipids had a large amount of polyunsaturated fatty acids that were absent in cow resulting in an unsaturation index (I(U)) four-fold higher than that of cow. We identified a novel FA with a molecular mass of 267 mass units in the lens epithelial layer of the toothfish that accounted for well over 50% of the FA abundance. The unidentified lipid in the toothfish lens epithelia corresponds to either an odd-chain (17 carbons) FA or a furanoid. We conclude that long-lived fishes are likely good animal models of lens crystallin solubility and may model post-translational modifications and solubility changes better than short-lived animal models.