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Chris G Gill - One of the best experts on this subject based on the ideXlab platform.
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Direct, Isomer-Specific Quantitation of Polycyclic Aromatic Hydrocarbons in Soils Using Membrane Introduction Mass Spectrometry and Chemical Ionization.
Analytical chemistry, 2020Co-Authors: Gregory W. Vandergrift, Erik T Krogh, Chris G GillAbstract:Polycyclic aromatic hydrocarbons (PAHs) are routinely screened for in soils, where quantitation of structural isomers is critical due to varying toxicity within PAH isomer classes. While chromatographic methods provide isomer resolution, such strategies are cost and time intensive. To address these challenges, we present condensed phase membrane introduction Mass Spectrometry using liquid electron ionization/chemical ionization (CP-MIMS-LEI/CI) as a direct Mass Spectrometry technique that provides rapid, quantitative results for PAH isomer measurements in soil samples. A methanol acceptor phase is flowed through a probe-mounted polydimethylsiloxane hollow fiber membrane directly immersed into a dichloromethane/soil slurry. PAHs and dichloromethane co-permeate the membrane into the acceptor solvent, whereas particulates and charged matrix components remain in the sample. A nanoflow of the membrane permeate is then directly infused into a LEI/CI interfaced triple quadrupole Mass spectrometer. Diagnostic PAH adduct ions were formed at either M + 45 ([M + CH2Cl + CH3OH-HCl]+) or M + 47 ([M + CHCl2-HCl]+). This allowed the development of specific MS/MS transitions for individual PAH isomers. These transitions were subsequently used for the direct analyses of PAHs in real soils where CP-MIMS-LEI/CI was shown to be rapid (15 soil samples/h) and sensitive (ng/g level detection limits). CP-MIMS-LEI/CI results compared well to those obtained using GC-MS (average percent difference of -9% across 9 PAHs in 8 soil samples), presenting a compelling argument for direct, quantitative screening of PAHs in soils by CP-MIMS-LEI/CI, particularly given the simple workflow and short analytical duty cycle.
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Condensed Phase Membrane Introduction Mass Spectrometry with In Situ Liquid Reagent Chemical Ionization in a Liquid Electron Ionization Source (CP-MIMS-LEI/CI).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Gregory W. Vandergrift, Erik T Krogh, William Lattanzio-battle, Chris G GillAbstract:Direct Mass Spectrometry has grown significantly due to wide applicability, relative ease of use, and high sample throughput. However, many current direct Mass Spectrometry methods are largely based on ambient ionization techniques that can suffer from matrix effects and poor selectivity. A strategy that addresses these shortcomings is condensed phase membrane introduction Mass Spectrometry-liquid electron ionization utilizing in situ liquid reagent chemical ionization (CP-MIMS-LEI/CI). In CP-MIMS measurements, a semipermeable hollow fiber polydimethylsiloxane membrane probe is directly immersed into a complex sample. Neutral, hydrophobic analytes permeating the membrane are entrained by a continuously flowing liquid acceptor phase (nL/min) to an LEI/CI source, where the liquid is nebulized, followed by analyte vaporization and ionization. This study marks the first intentional exploitation of the liquid CP-MIMS acceptor phase as an in situ means of providing liquid chemical ionization (CI) reagents for improved analyte sensitivity and selectivity (CP-MIMS-LEI/CI). Acetonitrile and diethyl ether were used as a combination acceptor phase/CI proton transfer reagent system for the direct analysis of dialkyl phthalates. Using isotopically labeled reagents, the gas phase ionization mechanism was found to involve reagent autoprotonation, followed by proton transfer to dialkyl phthalates. A demonstration of the applicability of CP-MIMS-LEI/CI for rapid and sensitive screening of bis(2-ethylhexyl) phthalate in house dust samples is presented. The detection limit in house dust (6 mg/kg) is comparable to that obtained by conventional analyses, but without time-consuming sample workup or chromatographic separation steps.
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Direct analysis of naphthenic acids in constructed wetland samples by condensed phase membrane introduction Mass Spectrometry.
The Science of the total environment, 2020Co-Authors: Kyle D. Duncan, Joseph Monaghan, Larissa C. Richards, Monique C. Simair, Chukwuemeka Ajaero, Kerry M. Peru, Vanessa Friesen, Dena W. Mcmartin, John V. Headley, Chris G GillAbstract:Abstract The application of direct Mass Spectrometry techniques to the analysis of complex samples has a number of advantages including reduced sample handling, higher sample throughput, in situ process monitoring, and the potential for adaptation to on-site analysis. We report the application of a semi-permeable capillary hollow fibre membrane probe (immersed directly into an aqueous sample) coupled to a triple quadrupole Mass spectrometer by a continuously flowing methanol acceptor phase for the rapid analysis of naphthenic acids with unit Mass resolution. The intensity of the naphthenic acid-associated peaks in the Mass spectrum are normalized to an internal standard in the acceptor phase for quantitation and the relative abundance of the peaks in the Mass spectrum are employed to monitor compositional changes in the naphthenic acid mixture using principle component analysis. We demonstrate the direct analysis of a synthetic oil sands process-affected water for classical naphthenic acids (CnH2n+zO2) as they are attenuated through constructed wetlands containing sedge (Carex aquatilis), cattail (Typha latifolia), or bulrush (Schoenoplectus acutus). Quantitative results for on-line membrane sampling compare favourably to those obtained by solid-phase extraction high-resolution Mass Spectrometry. Additionally, chemometric analysis of the Mass spectra indicates a clear discrimination between naphthenic acid-influenced and natural background waters. Furthermore, the compositional changes within complex naphthenic acid mixtures track closely with the degree of attenuation. Overall, the technique is successful in following changes in both the concentration and composition of naphthenic acids from synthetic oil sands process-affected waters, with the potential for high throughput screening and environmental forensics.
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Direct Measurement of Acid Dissociation Constants of Trace Organic Compounds at Nanomolar Levels in Aqueous Solution by Condensed Phase-Membrane Introduction Mass Spectrometry.
Environmental toxicology and chemistry, 2019Co-Authors: Jackelyn F. Feehan, Chris G Gill, Joseph Monaghan, Erik T KroghAbstract:We report the use of condensed phase-membrane introduction Mass Spectrometry as a novel method for the determination of acid dissociation constants for hydrophobic organic acids in aqueous solution at nanomolar concentrations. The technique is based on the pH-dependent permeation of analytes through a semipermeable polydimethylsiloxane membrane probe that is immersed directly in aqueous samples. We describe the method and report the dissociation constant (pKa ) values for compounds of biological and environmental relevance, including contaminants, pharmaceuticals, and naphthenic acids. The approach can be applied to individual compounds, combined suites, and complex mixtures at parts-per-billion levels. We report pKa values for 10 carboxylic acids with precision estimates and relative errors (where reliable literature values are available) of
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Direct quantitation and characterization of fatty acids in salmon tissue by condensed phase membrane introduction Mass Spectrometry (CP-MIMS) using a modified donor phase
Analytical and Bioanalytical Chemistry, 2019Co-Authors: Scott A. Borden, Erik T Krogh, Hannah N. Damer, Chris G GillAbstract:Existing Mass spectrometric methods for the analysis of fatty acids often require derivatization, chromatographic separations, and/or extensive sample preparation. Direct Mass Spectrometry strategies can avoid these requirements, but may also suffer from poor quantitation and/or lack of sensitivity. Condensed phase-membrane introduction Mass Spectrometry (CP-MIMS) provides direct quantitative measurements of analytes in complex samples with little or no sample preparation. CP-MIMS uses a semipermeable membrane to transfer neutral, hydrophobic compounds from real-world samples to a Mass spectrometer. The results presented utilize aqueous/organic sample solvent (donor) mixtures to allow for the sensitive (pptr) detection of a range of fatty acids. The relative sensitivity across a homologous series of fatty acids is observed to change, favoring short- or long-chain fatty acids, depending on the amount of miscible co-solvent added to the donor phase. Further, lithium acetate added online via the acceptor phase was used in tandem Mass Spectrometry experiments to determine the location of double bonds in polyunsaturated fatty acids (PUFAs). The method was applied to direct measurements and structural determinations for selected PUFAs in salmon tissue samples. Standard addition was employed to quantify the amount of PUFAs in a variety of salmon samples, yielding 0.27–0.42 and 0.40–0.84 w / w % for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), respectively, for Sockeye and Chinook salmon, in good agreement with the literature. This work presents, to our knowledge, the first use of CP-MIMS for the direct analysis of fatty acids in oily foodstuff samples. Graphical abstract ᅟ
Erik T Krogh - One of the best experts on this subject based on the ideXlab platform.
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Direct, Isomer-Specific Quantitation of Polycyclic Aromatic Hydrocarbons in Soils Using Membrane Introduction Mass Spectrometry and Chemical Ionization.
Analytical chemistry, 2020Co-Authors: Gregory W. Vandergrift, Erik T Krogh, Chris G GillAbstract:Polycyclic aromatic hydrocarbons (PAHs) are routinely screened for in soils, where quantitation of structural isomers is critical due to varying toxicity within PAH isomer classes. While chromatographic methods provide isomer resolution, such strategies are cost and time intensive. To address these challenges, we present condensed phase membrane introduction Mass Spectrometry using liquid electron ionization/chemical ionization (CP-MIMS-LEI/CI) as a direct Mass Spectrometry technique that provides rapid, quantitative results for PAH isomer measurements in soil samples. A methanol acceptor phase is flowed through a probe-mounted polydimethylsiloxane hollow fiber membrane directly immersed into a dichloromethane/soil slurry. PAHs and dichloromethane co-permeate the membrane into the acceptor solvent, whereas particulates and charged matrix components remain in the sample. A nanoflow of the membrane permeate is then directly infused into a LEI/CI interfaced triple quadrupole Mass spectrometer. Diagnostic PAH adduct ions were formed at either M + 45 ([M + CH2Cl + CH3OH-HCl]+) or M + 47 ([M + CHCl2-HCl]+). This allowed the development of specific MS/MS transitions for individual PAH isomers. These transitions were subsequently used for the direct analyses of PAHs in real soils where CP-MIMS-LEI/CI was shown to be rapid (15 soil samples/h) and sensitive (ng/g level detection limits). CP-MIMS-LEI/CI results compared well to those obtained using GC-MS (average percent difference of -9% across 9 PAHs in 8 soil samples), presenting a compelling argument for direct, quantitative screening of PAHs in soils by CP-MIMS-LEI/CI, particularly given the simple workflow and short analytical duty cycle.
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Condensed Phase Membrane Introduction Mass Spectrometry with In Situ Liquid Reagent Chemical Ionization in a Liquid Electron Ionization Source (CP-MIMS-LEI/CI).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Gregory W. Vandergrift, Erik T Krogh, William Lattanzio-battle, Chris G GillAbstract:Direct Mass Spectrometry has grown significantly due to wide applicability, relative ease of use, and high sample throughput. However, many current direct Mass Spectrometry methods are largely based on ambient ionization techniques that can suffer from matrix effects and poor selectivity. A strategy that addresses these shortcomings is condensed phase membrane introduction Mass Spectrometry-liquid electron ionization utilizing in situ liquid reagent chemical ionization (CP-MIMS-LEI/CI). In CP-MIMS measurements, a semipermeable hollow fiber polydimethylsiloxane membrane probe is directly immersed into a complex sample. Neutral, hydrophobic analytes permeating the membrane are entrained by a continuously flowing liquid acceptor phase (nL/min) to an LEI/CI source, where the liquid is nebulized, followed by analyte vaporization and ionization. This study marks the first intentional exploitation of the liquid CP-MIMS acceptor phase as an in situ means of providing liquid chemical ionization (CI) reagents for improved analyte sensitivity and selectivity (CP-MIMS-LEI/CI). Acetonitrile and diethyl ether were used as a combination acceptor phase/CI proton transfer reagent system for the direct analysis of dialkyl phthalates. Using isotopically labeled reagents, the gas phase ionization mechanism was found to involve reagent autoprotonation, followed by proton transfer to dialkyl phthalates. A demonstration of the applicability of CP-MIMS-LEI/CI for rapid and sensitive screening of bis(2-ethylhexyl) phthalate in house dust samples is presented. The detection limit in house dust (6 mg/kg) is comparable to that obtained by conventional analyses, but without time-consuming sample workup or chromatographic separation steps.
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Direct Measurement of Acid Dissociation Constants of Trace Organic Compounds at Nanomolar Levels in Aqueous Solution by Condensed Phase-Membrane Introduction Mass Spectrometry.
Environmental toxicology and chemistry, 2019Co-Authors: Jackelyn F. Feehan, Chris G Gill, Joseph Monaghan, Erik T KroghAbstract:We report the use of condensed phase-membrane introduction Mass Spectrometry as a novel method for the determination of acid dissociation constants for hydrophobic organic acids in aqueous solution at nanomolar concentrations. The technique is based on the pH-dependent permeation of analytes through a semipermeable polydimethylsiloxane membrane probe that is immersed directly in aqueous samples. We describe the method and report the dissociation constant (pKa ) values for compounds of biological and environmental relevance, including contaminants, pharmaceuticals, and naphthenic acids. The approach can be applied to individual compounds, combined suites, and complex mixtures at parts-per-billion levels. We report pKa values for 10 carboxylic acids with precision estimates and relative errors (where reliable literature values are available) of
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Direct quantitation and characterization of fatty acids in salmon tissue by condensed phase membrane introduction Mass Spectrometry (CP-MIMS) using a modified donor phase
Analytical and Bioanalytical Chemistry, 2019Co-Authors: Scott A. Borden, Erik T Krogh, Hannah N. Damer, Chris G GillAbstract:Existing Mass spectrometric methods for the analysis of fatty acids often require derivatization, chromatographic separations, and/or extensive sample preparation. Direct Mass Spectrometry strategies can avoid these requirements, but may also suffer from poor quantitation and/or lack of sensitivity. Condensed phase-membrane introduction Mass Spectrometry (CP-MIMS) provides direct quantitative measurements of analytes in complex samples with little or no sample preparation. CP-MIMS uses a semipermeable membrane to transfer neutral, hydrophobic compounds from real-world samples to a Mass spectrometer. The results presented utilize aqueous/organic sample solvent (donor) mixtures to allow for the sensitive (pptr) detection of a range of fatty acids. The relative sensitivity across a homologous series of fatty acids is observed to change, favoring short- or long-chain fatty acids, depending on the amount of miscible co-solvent added to the donor phase. Further, lithium acetate added online via the acceptor phase was used in tandem Mass Spectrometry experiments to determine the location of double bonds in polyunsaturated fatty acids (PUFAs). The method was applied to direct measurements and structural determinations for selected PUFAs in salmon tissue samples. Standard addition was employed to quantify the amount of PUFAs in a variety of salmon samples, yielding 0.27–0.42 and 0.40–0.84 w / w % for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), respectively, for Sockeye and Chinook salmon, in good agreement with the literature. This work presents, to our knowledge, the first use of CP-MIMS for the direct analysis of fatty acids in oily foodstuff samples. Graphical abstract ᅟ
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Online measurement of phthalate–particulate matter interactions by membrane introduction Mass Spectrometry (MIMS)
Journal of environmental science and health. Part A Toxic hazardous substances & environmental engineering, 2018Co-Authors: Martin A. Angelstad, Erik T Krogh, George R. Agnes, Chris G GillAbstract:To enable further study and assessment of indoor inhalation exposure risk, an online apparatus enabling measurement of semi-volatile compound partitioning on household particulates was developed. An example for use of the apparatus is described using dimethyl phthalate (DMP). The system employs direct measurement by membrane introduction Mass Spectrometry (MIMS). The MIMS system was calibrated using known gas phase DMP concentrations produced by gravimetrically calibrated permeation devices. The quantity of DMP sorbed by particles is described first using a model particle type, a reverse-phase liquid chromatography packing material, and then with a household dust sample. In addition, the desorption of semi-volatile compounds from a household dust sample was monitored using the apparatus, and characteristic fragment ion signals for phthalate compounds were observed.
Marcos N. Eberlin - One of the best experts on this subject based on the ideXlab platform.
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natural and artificial markers of gasoline detected by membrane introduction Mass Spectrometry
Analytical Methods, 2011Co-Authors: Regina Sparrapan, Marcos N. Eberlin, Rosana M. AlbericiAbstract:A few hydrocarbons in gasoline display relatively high solubility in water and may function therefore as its characteristic set of natural markers. These markers are detected from an aqueous gasoline extract viamembrane introduction Mass Spectrometry (MIMS) producing characteristic chemical profiles. MIMS adds a second selectivity criterion detecting only the water soluble hydrocarbons that most easily permeate through a silicone membrane. MIMS screening and the use of artificial markers for gasoline with similar chemical properties (high water solubility and membrane permeability) as those of its natural markers is proposed. MIMS provides a reliable screening method for natural and artificial markers in gasoline for its typification and to monitor adulteration and origin.
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Quantitation of trace phenolic compounds in water by trap-and-release membrane introduction Mass Spectrometry after acetylation.
Rapid communications in mass spectrometry : RCM, 2008Co-Authors: Regina Sparrapan, Marcos N. Eberlin, Rosana M. AlbericiAbstract:Trap-and-release membrane introduction Mass Spectrometry (TR hence, T&R-MIMS of the acetylated phenols provides lower and more uniform limits of detection (LODs) (2-15 microg L(-1)) than those obtained by direct T&R-MIMS analysis of the non-derivatized phenols.
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Chloroform formation by chlorination of aqueous algae suspensions: online monitoring via membrane introduction Mass Spectrometry
Journal of the Brazilian Chemical Society, 2008Co-Authors: João Tito Borges, Marcos N. Eberlin, Regina Sparrapan, José Roberto Guimarães, Rodinei AugustiAbstract:A tecnica MIMS (membrane introduction Mass Spectrometry) foi utilizada para monitorar a formacao de cloroformio durante a cloracao de suspensoes aquosas de varias especies brasileiras de algas verdes e azuis (Microcystis panniformis, Selenastrum sp., Scenedesmus sp., Monoraphidium sp. (strain 354), Monoraphidium sp. (strain 960), and Staurastrum sp.). Foram avaliadas as influencias de parâmetros como temperatura, pH, concentracao inicial de hipoclorito de sodio, filtracao e tempo de reacao. Foi constatado que o teor de cloroformio e fortemente dependente da especie de alga e tambem e favorecido com o aumento da temperatura, pH, dosagem de cloro inicial e do tempo de reacao. Amostras de suspensoes de algas submetidas a filtracao produziram menores quantidades de cloroformio em comparacao com as amostras brutas.
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Oxidation of Sodium Dodecylbenzenesulfonate with Chrysotile: On-line Monitoring by Membrane Introduction Mass Spectrometry
Journal of Surfactants and Detergents, 2007Co-Authors: Adriano Fachini, Maria A. Mendes, Inés Joekes, Marcos N. EberlinAbstract:Chrysotile was tested for anionic surfactant (SDBS) removal from aqueous solutions. Results showed that the reduction was due to a catalytic process onto the chrysotile surface, which is formed of hydroxyl groups. Trap and release membrane introduction Mass Spectrometry using a modified direct insertion membrane probe (DIMP-T&R-MIMS) was used to monitor on-line SDBS oxidation by air in an aqueous alkaline media containing chrysotile. It was possible to estimate the amount of CO_2 formed in SDBS catalyzed reaction through quantification of CO_2 formed by the hydrolysis of MgCO_3. A Mass balance for the SDBS reaction is proposed. DIMP-T&R-MIMS monitoring identified no VOCs or SVOCs as degradation intermediates, but CO_2 was detected to account for SDBS degradation. Hence, simple chrysotile adsorption is excluded as a main process of SDBS consumption, and a “SDBS in-CO_2 out” mechanism on the chrysotile surface accounts for the experimental observations.
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On-line monitoring of bioreductions via membrane introduction Mass Spectrometry.
Biotechnology and bioengineering, 2005Co-Authors: Cíntia D.f. Milagre, Lilian Lúcia Da Rocha, Humberto M. S. Milagre, J. Augusto R. Rodrigues, Leonardo S. Santos, Marcos N. EberlinAbstract:Real-time and on-line continuous monitoring of reactants, intermediates, and final products for dicar- bonyl compound bioreductions in a continuous plug flow reactor packed with baker's yeast (Saccharomyces cere- visiae) whole cells immobilized on calcium alginate beads was performed by membrane introduction Mass spectro- metry (MIMS) via selective ion monitoring. 2005 Wiley Periodicals, Inc.
R. Graham Cooks - One of the best experts on this subject based on the ideXlab platform.
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Membrane introduction Mass Spectrometry for monitoring complexation equilibria of β-cyclodextrin with substituted benzenes
The Analyst, 2003Co-Authors: Rodinei Augusti, Maciej Turowski, R. Graham CooksAbstract:Membrane introduction Mass Spectrometry (MIMS) was used to monitor complexation reactions between β-cyclodextrin (CD) and a series of benzene derivatives in aqueous solution. The equilibrium constants for benzene, chlorobenzene, bromobenzene, iodobenzene, toluene, cyanobenzene and nitrobenzene were determined. The suitability of MIMS for monitoring complexation reactions of organic compounds with host molecules was demonstrated. Structure–activity relationship analysis shows that the inclusion phenomena are driven by a variety of chemical forces, of which hydrophobicity is predominant for non-polar compounds, but not the only factor for more polar ones.
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Determination of pentachlorophenol by negative ion chemical ionization with membrane introduction Mass Spectrometry
The Analyst, 2002Co-Authors: Thomas A. Blake, Xubin Zheng, Tenna Aggerholm, Frants Roager Lauritsen, R. Graham CooksAbstract:Pentachlorophenol (PCP) was used as a model compound to explore the potential of desorption chemical ionization (DCI) in the determination of polychlorinated pesticides using membrane introduction Mass Spectrometry (MIMS). A direct insertion membrane probe was modified so that a chemical ionization plasma could be established at the membrane surface. Using selected ion monitoring (SIM) in a tandem triple quadrupole Mass spectrometer with isobutane chemical ionization (CI), the PCP detection limit under positive chemical ionization is 20 ppb whereas negative CI gives detection limits in the low ppb range. This performance is achieved without any pre-treatment or derivatization of the sample. Negative ion CI gives a signal that is linear over a concentration range of 2–1000 ppb. Comparison of data obtained with low ppb samples of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol suggests that the sensitivity of this analytical procedure increases with increase in the number of electronegative substituents in the molecule.
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Single-sided membrane introduction Mass Spectrometry for on-line determination of semi-volatile organic compounds in air.
The Analyst, 2001Co-Authors: Leah S. Riter, Zoltan Takats, R. Graham CooksAbstract:Construction, optimization, and testing of a novel single-sided configuration for a semi-permeable [poly(dimethylsiloxane); PDMS] membrane introduction system for Mass Spectrometry is described. On-line detection of semi-volatile organic compounds of environmental interest is shown, including lindane (a pesticide), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) (an explosive), butylated hydroxytoluene (BHT) (an antioxidant), 1,2-dichlorobenzene, dimethylmethyl phosphonate (DMMP) (a chemical warfare agent simulant) and naphthalene. The technique has limits of detection in the sub-ppb range, with rise times of 4 to 7 s and fall times of 12 to 36 s and a response that is linear over 4 orders of magnitude (from 0.1 ppb to 1000 ppb for DMMP). The cycle time, from crude air sampling to acquisition of results, is approximately 1 min. No sample preparation is necessary.
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Affinity liquid membrane introduction Mass Spectrometry
Analytica Chimica Acta, 1999Co-Authors: Rudolph C. Johnson, Kim J. Koch, R. Graham CooksAbstract:Abstract A Mass-spectrometer membrane introduction system, modeled after affinity chromatography, utilizes chemically modified low vapor-pressure liquids to selectively bind and release aryl aldehydes from multi-component aqueous sample streams. Polyphenyl ether, a slightly polar liquid, was admixed with an optimum loading of 10% octadecylamine (w/w) and coated on a microporous support to create a hydrophobic, semipermeable membrane containing primary amine functionalities. A 1.9-cm 2 surface-area membrane interface was built in-house for these experiments and optimized for temperature (71°C), flow rate (1 ml/min), additive loading, and thickness (0.10 mm). Benzaldehyde was selectively bound to this membrane under standard operating conditions with an efficiency of ca. 50%, defined as analyte response during release from the membrane (pH 1) as compared to response during loading (pH 7.8). Analytes were introduced into an ion-trap Mass spectrometer in a helium stream via a jet separator. Total analysis periods were ca. 20 min for concentrations between 50 ppb and 50 ppm, with a standard deviation of 7% for similar concentration samples. Selective liquid-membrane interfaces represent new technology for membrane introduction Mass Spectrometry.
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Sampling of aryldiazonium, anilino, and aryl radicals by membrane introduction Mass Spectrometry: Thermolysis of aromatic diazoamino compounds
Journal of the American Society for Mass Spectrometry, 1998Co-Authors: Narasimhan Kasthurikrishnan, R. Graham Cooks, Malcolm J. ThompsonAbstract:Membrane introduction Mass Spectrometry (MIMS) is used to sample free radicals generated by thermolysis at atmospheric pressure. This is done by heating the solid sample in a custom-made probe that is fitted with a silicone membrane to allow selective and rapid introduction of the pyrolysates into the ion source of a triple quadrupole Mass spectrometer. Phenyldiazonium radical (C_6H_5N _2 ^· ) and some of its ring-substituted analogs, the methoxy anilino radical CH_3OC_6H_4NH^·, and aryl radicals are generated by gas phase thermolysis of symmetrical aryl diazoamino compounds (ArNH-N_2Ar). The radicals are identified by measurement of their ionization energies (IE) using threshold ionization efficiency data. A linear correlation between the ionization energy of the phenyldiazonium radicals and their Brown σ^+ values is observed, and this confirms the formation of these species and validates the applicability of MIMS in sampling these radicals. The ionization energies of the aryldiazonium radicals are estimated as IE ( p -CH_3O-C_6H_4N _2 ^· ), 6.74 ± 0.2 eV; IE ( p -CH_3-C_6H_4N _2 ^· ), 7.72 ± 0.2 eV; IE (C_6H_5N _2 ^· ), 7.89 ± 0.2 eV; IE ( m -Cl-C_6H_4N _2 ^· ), 7.91 ± 0.2 eV; IE ( p -F-C_6H _4 ^· N _2 ^· ), 8.03 ± 0.2 eV; and IE ( m -NO_2-C_6H_4N _2 ^· ), 8.90 = 0.2 eV. The ionization energies of the aryl radicals are estimated as IE ( p -CH_3O-C_6H _4 ^· ), 7.33 ± 0.2 eV; IE ( p -CH_3-C_6H _4 ^· ), 8.31 ± 0.2 eV; IE (C_6H _5 ^· ), 8.44 ± 0.2 eV; IE ( m -Cl-C_6H _4 ^· ), 8.50 ± 0.2 eV and IE ( p -F-C_6H _4 ^· ), 8.54 ± 0.2 eV. Also, the ionization energy of the p -methoxyanilino radical ( p -CH_3O-C_6H_4NH^·) is estimated as 7.63 ± 0.2 eV.
P H Hemberger - One of the best experts on this subject based on the ideXlab platform.
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membrane introduction Mass Spectrometry trends and applications
Mass Spectrometry Reviews, 2000Co-Authors: Rudolph C. Johnson, M E Cisper, Todd M Allen, R. G. Cooks, P H HembergerAbstract:Recent advances in membrane introduction Mass Spectrometry (MIMS) are reviewed. On-line monitoring is treated by focusing on critical variables, including the nature and dimensions of the membrane, and the analyte vapor pressure, diffusivity, and solubility in the membrane barrier. Sample introduction by MIMS is applied in (i) on-line monitoring of chemical and biological reactors, (ii) analysis of volatile organic compounds in environmental matrices, including air, water and soil, and (iii) in more fundamental studies, such as measurements of thermochemical properties, reaction mechanisms, and kinetics. New semipermeable membranes are discussed, including those consisting of thin polymers, low vapor pressure liquids, and zeolites. These membranes have been used to monitor polar compounds, selectively differentiate compounds through affinity-binding, and provide isomer differentiation based on molecular size. Measurements at high spatial resolution, for example, using silicone-capped hypodermic needle inlets, are also covered, as is electrically driven sampling through microporous membranes. Other variations on the basic MIMS experiment include analyte preconcentration through cryotrapping (CT–MIMS) or trapping in the membrane (trap-and-release), as well as differential thermal release methods and reverse phase (i.e., organic solvent) MIMS. Method limitations center on semivolatile compounds and complex mixture analysis, and novel solutions are discussed. Semivolatile compounds have been monitored with thermally assisted desorption, ultrathin membranes and derivatization techniques. Taking advantage of the differences in time of membrane permeation, mixtures of structurally similar compounds have been differentiated by using sample modulation techniques and by temperature-programmed desorption from a membrane interface. Selective ionization techniques that increase instrument sensitivity towards polar compounds are also described, and comparisons are made with other direct sampling (nonchromatographic) methods that are useful in mixture analysis. © 2000 John Wiley & Sons, Inc., Mass Spec Rev 19: 1–37, 2000
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Real-time broad spectrum characterization of hazardous waste by membrane introduction Mass Spectrometry. 1998 annual progress report
1998Co-Authors: P H Hemberger, M. CisperAbstract:'As of May 1, 1998, the authors have designed and tested the rare gas ionization source and the associated ion optics. Ions are generated in a microwave plasma which can be supported by helium or argon from room air. A series of extraction and focusing lenses followed by a linear quadrupole serves to inject ions into the ion trap. Injection efficiency and favorable trapping of externally-generated ions are dependent on several parameters including lens potentials, quadrupole operation, buffer gas pressure, kinetic energy of the injected ions, and amplitude of the trapping potential. They have investigated rf-only operation of the linear quadrupole. RF/DC operation will be studied as a means for further reducing interferences. A publication on this work has been submitted to Int. J. Mass. Spectrom. Ion Proc. To date they have used MIMS to detect 40 volatile and SVOCs without preconcentration, primarily from an air matrix. The 40 analytes range in boiling point from 21 to 279 C and include chlorinated and oxygenated solvents, chlorophenols, polyaromatic hydrocarbons, and substituted benzenes. Using MIMS, they have demonstrated the direct, simultaneous detection of a volatile organic compound, a semi-volatile organic compound, and an organometallic compound with a single analytical technique in near real-time for two waste streams, air and water. To their knowledge, this is the first time this has been accomplished. They have investigated the analysis of several organometallic compounds containing heavy metals by MIMS. These include lead and tin compounds. When these molecules are analyzed, organic fragment ions are observed. However, neither the intact molecular ion, nor the metal ion species are seen in the Mass spectrum. These results are interesting because in the spectra of metal compounds most of the ion current is normally carried by metal-containing species [J. Charalambous, ed., Mass Spectrometry of Metal Compounds]. The authors speculate that it is oxygen, present either as a neutral or as an ionized species, that may be inhibiting the appearance of metal-containing fragment ions in certain cases. Oxygen is one of the predominating species in the ion trap environment in the experiment. Its high availability for secondary reactions as either a neutral or positively charged ion and the stability of possible products from these secondary processes may make the detection of metal-containing ions problematic in the current set-up. The formation of highly refractory neutral metal oxides, for example, would preclude the detection of metal-containing fragment ions. They are investigating experimental means to test the questions that have been raised by these observations. Other ion trap instruments in the lab with additional capabilities to study ion/molecule chemistry may provide help in testing and resolving this issue.'
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The Direct Analysis of Semi-volatile Organic Compounds by Membrane Introduction Mass Spectrometry
Rapid Communications in Mass Spectrometry, 1997Co-Authors: M E Cisper, P H HembergerAbstract:We present results for direct on-line detection of semi-volatile compounds in air using membrane introduction ion trap Mass Spectrometry. Brief sampling periods of 10 seconds to 3 minutes produced linear and reproducible data for concentrations ranging from parts-per-trillion to parts-per-billion by volume. The method uses a composite membrane made by plasma deposition of a thin polydimethylsilicone layer on a microporous polypropylene support fiber. Charge exchange ionization was used for a variety of semi-volatile compounds and produced enhanced responses when compared to electron ionization. Among the semi-volatile species studied are dimethyl methylphosphonate, malathion, nitrobenzene, methyl salicylate, 2-chlorophenol, cyclohexanol, diethyl malonate and naphthalene. We also demonstrate direct analysis of semi-volatile compounds in aqueous solution with the composite membrane by the detection of 2-chlorophenol in water using both electron ionization and proton transfer chemical ionization. © 1997 John Wiley & Sons, Ltd.
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analysis of polar organic compounds using charge exchange ionization and membrane introduction Mass Spectrometry
Analytical Chemistry, 1996Co-Authors: M E Cisper, A W Garrett, And D Cameron, P H HembergerAbstract:Charge exchange ionization in conjunction with membrane introduction Mass Spectrometry provides a sensitive method for the detection of polar volatile organic compounds and semivolatile compounds in air. Sample introduction into an ion trap Mass spectrometer was accomplished with a hollow fiber silicone membrane assembly. Atmospheric oxygen, which diffuses through the membrane, was used as the charge exchange reagent. Chemical ionization parameters were optimized using methyl ethyl ketone (2-butanone) standards in air. Several other oxygen-containing compounds, including acetone (2-propanone), methyl isobutyl ketone (4-methyl-2-pentanone), propanal, isopropyl alcohol (2-propanol), cyclohexanol, dimethyl sulfoxide (sulfinylbismethane), 2-(diethylamino)ethanol, and dimethyl methylphosphonate were analyzed with this technique. This method was used to obtain Mass spectra for a variety of classes of compounds and produced a 4−20-fold improvement in response for all of the polar compounds we examined when compa...
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Online Detection of Volatile Organic Compounds in Air at Parts-per-Trillion Levels by Membrane Introduction Mass Spectrometry
Analytical Chemistry, 1995Co-Authors: M E Cisper, Chris G Gill, Lisa E. Townsend, P H HembergerAbstract:We describe the use of a two-stage membrane sampling system coupled with an ion trap spectrometer for the direct analysis of volatile organic compounds in air with quantitation limits to low parts-per-billion levels and detection to parts-per-trillion levels. Toluene, carbon tetrachloride, trichloroethane, and benzene were used in these studies. We have obtained linear calibration curves from approximately 3 to 3000 ppb by volume for these compounds. The magnitude of instrument response is essentially independent of air flow rate from 0.2 to >3 L/min; response times are 60-90 s. Additionally, the same membrane interface can be used for the sequential analysis of water and soil, providing a sensitive and versatile analytical tool. 22 refs., 5 figs., 1 tab.