Trace moisture emissions from heated metal surfaces in hydrogen service

Negative ions of dicarboxylic acids observed by plasma chromatography and atmospheric pressure ionization mass spectrometry

Detection of a thermally unstable intermediate in the Wittig reaction using low-temperature liquid secondary ion and atmospheric pressure ionization mass spectrometry

In general, ionization of analytes in atmospheric pressure ionization mass spectrometry (API-MS) in positive ion mode results in the formation of protonated molecules ([M + H]+ ) and/or cationized molecules (e.g., [M + Na]+ ). The formation of specific [M - H]+ cations in the API process is of significant interest for further investigation. The ionization processes of 2-(diphenylsilyl)-1-phenyl-cyclopropanecarboxylate esters were investigated using electrospray ionization (ESI)-MS and atmospheric pressure chemical ionization-MS in positive ion mode. Theoretical calculations were carried out with the Gaussian 03 program using the density functional theory (DFT) method at the B3LYP/6-311 + G(2d,p) level. The anomalous [M - H]+ ion and the regular [M + Na]+ ion were both observed using ESI-MS. Interestingly, no [M + H]+ ion was obtained in the ESI-MS analysis, and acidification of the ESI solvent accelerated the formation of [M - H]+ rather than [M + H]+ ion. DFT calculations for the typical methyl 2-(diphenylsilyl)-1-phenyl-cyclopropanecarboxylate (1) indicated that the [1 + H]+ ion can thermodynamically and kinetically undergo facile H2 elimination to generate [1 - H]+ . The favorable formation of [M - H]+ ions in these compounds is attributed to the unique diphenylhydrosilyl group in their structure. The [M + H]+ ion formed easily underwent H2 elimination to produce the [1 - H]+ ion in the API source, and thus, acidification of the ESI solvent apparently accelerates the formation of the [1 - H]+ ion.

Comparison of on-line coupling of ion-chromatography with atmospheric pressure ionization mass spectrometry and with inductively coupled plasma mass spectrometry as tools for the ultra-trace analysis of bromate in surface water samples

The use of atmospheric pressure ionization at −78 °C for the analysis of a thermally unstable compound, 2,5-dimethylene-2,5-dihydrothiophene, dissolved in methylene chloride is demonstrated with a home-built low-temperature electrospray source connected to a quadruple mass analyzer. To prevent the analyte molecule from polymerizing at elevated temperatures, the sample solution was maintained at −78 °C in the dry-ice-cooled sample injection and sample loop units. The solution was delivered to the spray needle by compressing the nitrogen gas in a syringe which was connected to the sample loop by a Teflon tube. At such low temperature, a strong ion signal was obtained from the analyte molecule as a result of corona discharge ionization.

ABSTRACTGaseous impurities in the chamber of a SHS2800ε rapid thermal processor were quantitatively measured by using atmospheric pressure ionisation mass spectrometry (APIMS). APIMS is a very sensitive technique to detect trace impurities in a bulk (1 atm) gas. A wide dynamic range (0.1 ppb - 10 ppm) measurement was successfully performed, which allowed in-situ monitoring of impurities during RTP. This work reports the fundamental behaviour of ambient impurities originating from different sources. The sources discussed in this paper are threefold: system background, wafer loading, and the wafer itself. Ambient management requires a better understanding of the independent contribution of each source on processing.

Determination of atractyloside in Callilepis laureola using solid-phase extraction and liquid chromatography–atmospheric pressure ionisation mass spectrometry

Gas phase anion reactions at atmospheric pressure : Atmospheric pressure ionization mass spectrometric studies related to the electron-capture detector

Hongmu, a Chinese customary noun representing 29 kinds of wood species such as some Pterocarpus species (abbreviated as spp. hereinafter), Dalbergia spp. and Diospyros spp., is popular among Chinese people due to the furniture made from it. The slow regeneration of hongmu resources led to a decline in production, making hongmu prices high and illegal businesses profit from it. Therefore, it is necessary to identify and distinguish different varieties of hongmu for commercial trade. Herein, a cost-effective and rapid methodology was first developed via atmospheric pressure glow discharge mass spectrometry (APGD-MS) to classify three Dalbergia spp. and three Pterocarpus spp. Meanwhile, principal component analysis (PCA) was further applied to distinguish wood species and six kinds of hongmu extracts were able to be approximately separated into six units. Besides, hongmu could be clearly distinguished from their counterfeits, such as Guibourtia spp., using the method provided here. This method may provide a timely and necessary way for the determination of ingredients and identification of the authenticity of hongmu.

This chapter presents an overview about the principles and instrumentation of atmospheric pressure ionization mass spectrometry (MS), followed by the application of electrospray ionization (ESI) MS and liquid chromatography/MS (LC/MS) to oligomers and polymers. A catalyst to the development of techniques involving sprays as methods of sample introduction and/or ionization has been the pursuit of on-line coupling of LC/MS. The advantage of hyphenated LC/MS for obtaining information about chemical composition, resolution of overlapping charge envelopes in the electrospray ionization mass spectra of polymers, size-exclusion chromatography calibration, and complex mixture analysis have been highlighted. Thermospray was an earlier method developed as an LC/MS interface that employed heat instead of an electric field for generation of charged droplets. ESI MS has become the method of choice in general, when on-line LC/MS of various synthetic polymers is considered. Spraying in ESI is conducted at atmospheric pressure and ambient temperature.

Rate constants for the reactions of OH radicals with four C(6)-C(10) cycloalkenes have been measured at 297 ± 2 K using a relative rate technique. The rate constants (in units of 10(-11) cm(3) molecule(-1) s(-1)) were cyclohexene, 6.35 ± 0.12; cis-cyclooctene, 5.16 ± 0.15; cis-cyclodecene, 4.18 ± 0.06; and 1-methyl-1-cyclohexene, 9.81 ± 0.18, where the indicated errors are two least-squares standard deviations and do not include uncertainties in the rate constant for the reference compound 1,3,5-trimethylbenzene. In addition, a rate constant of (4.8 ± 1.3) × 10(-11) cm(3) molecule(-1) s(-1) was derived for the reaction of OH radicals with 1,6-hexanedial, relative to our measured rate constant for OH + cyclohexene. Analyses of products of the OH + cyclohexene, 1-methyl-1-cyclohexene, and cis-cyclooctene reactions by direct air sampling atmospheric pressure ionization mass spectrometry and/or by combined gas chromatography-mass spectrometry showed the presence of products attributed to cyclic 1,2-hydroxynitrates and the dicarbonyls 1,6-hexanedial, 6-oxo-heptanal, and 1,8-octanedial, respectively. These dicarbonyl products, which are those formed after decomposition of the intermediate cyclic 1,2-hydroxyalkoxy radicals, were quantified as their dioximes, with molar formation yields of 76 ± 10%, 82 ± 12%, and 84 ± 18% from the cyclohexene, 1-methyl-1-cyclohexene, and cis-cyclooctene reactions, respectively. Combined with literature data concerning 1,2-hydroxynitrate formation from OH + alkenes and the estimated fractions of the overall reactions proceeding by H-atom abstraction, 90 ± 12%, 95 ± 13% and 108 ± 20% of the products or reaction pathways from the OH radical-initiated reactions of cyclohexene, 1-methyl-1-cyclohexene, and cis-cyclooctene in the presence of NO are accounted for.

Combining linear retention index and electron ionization mass spectrometry for a reliable identification in nano liquid chromatography

Atmospheric pressure chemical ionization (APCI) sources operated with point to plane DC discharges ('Coronas') frequently suffer from point electrode degradation and potentially lead to oxidation and/or fragmentation of the generated analyte ions. It is postulated that these adverse effects are caused by the interaction of these ions with the discharge chemistry as well as en route to the mass analyzer region. The corona discharge metal point electrode is replaced by the conically shaped liquid effluent evolving from a fused-silica capillary, which is analogous but not identical to the Taylor cone formation in electrospray ionization. The liquid consisting of either pure water or water containing 0.1 %V formic acid is fed via a nano-flow delivery stage at typical flow rates between 1-800 μL/h. The liquid flow is continuously replenishing the surface of the point electrode. The source is directly coupled to the inlet capillary of appropriate mass spectrometers, e.g., the Bruker Daltonics and Agilent varieties. The actively pumped liquid flow is supplying a constant amount of the reagent gas (H2O) to the corona region in the 20 ppmV to 30 %V range, leading to controlled, very stable operation of the source. The typical light emission observed for corona discharges is in very close proximity to the aqueous surface. Analyte protonation is the dominating ionization pathway. The degree of primary analyte fragmentation is extremely low. We have developed a novel atmospheric pressure chemical ionization source designed for the hyphenation of nano-flow liquid chromatography and gas chromatography with atmospheric pressure ionization mass spectrometry. The proposed reaction mechanism including the electrochemistry occurring in the source along with formation of protonated analyte molecules via collision-induced dissociation (CID) is in full accord with the experimental results. The system exhibits an extremely stable performance over prolonged operation times, sole generation of protonated molecules, and low degree of analyte ion fragmentation.

Determination of the enantiomeric composition of a new insulin sensitizer in plasma samples from non-clinical and clinical investigations using chiral HPLC with electrospray tandem mass spectrometric detection

Molecular and enzymatic characterization of a levan fructotransferase from Microbacterium sp. AL-210