Directing a Non-Heme Iron(III)-Hydroperoxide Species on a Trifurcated Reactivity Pathway.

The reactivity of [FeIII (tpena)]2+ (tpena=N,N,N'-tris(2-pyridylmethyl)ethylenediamine-N'-acetate) as a catalyst for oxidation reactions depends on its ratio to the terminal oxidant H2 O2 and presence or absence of sacrificial substrates. The outcome can be switched between: 1) catalysed H2 O2 disproportionation, 2) selective catalytic oxidation of methanol or benzyl alcohol to the corresponding aldehyde, or 3) oxidative decomposition of the tpena ligand. A common mechanism is proposed involving homolytic O-O cleavage in the detected transient purple low-spin (S=1/2 ) [(tpenaH)FeIII O-OH]2+ . The resultant iron(IV) oxo and hydroxyl radical both participate in controllable hydrogen-atom transfer (HAT) reactions. Consistent with the presence of a weaker σ-donor carboxylate ligand, the most pronounced difference in the spectroscopic properties of [Fe(OOH)(tpenaH)]2+ and its conjugate base, [Fe(OO)(tpenaH)]+ , compared to non-heme iron(III) peroxide analogues supported by neutral multidentate N-only ligands, are slightly blue-shifted maxima of the visible absorption band assigned to ligand-to-metal charge-transfer (LMCT) transitions and, corroborating this, lower FeIII /FeII redox potentials for the pro-catalysts.

Interactions between nanoparticles and lung surfactant investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RATIONALE: Inhaled nanoparticles may cause adverse effects due to inactivation of lung surfactants. We have studied how three different nanoparticles interact with dipalmitoyl-phosphatidylcholine (DPPC), the main component in lung surfactant. METHODS: DPPC in solution was mixed with a suspension of nanoparticles, both in organic solvent, and allowed to interact for 40 min under conditions partly resembling the alveolar lining. Nanoparticles were isolated by centrifugation, washed, and re-suspended in ethanol/water 1:1 (v/v). The resulting solution was analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) using dihydroxybenzoic acid as matrix. RESULTS: The developed methodology was successfully applied for quantitative detection of phospholipid lung surfactant bound to three different types of nanoparticles. Titanium dioxide nanoparticles had a strong affinity for binding of lipid lung surfactant in contrast to pristine and methylated silica nanoparticles. When the concentration of lipid surfactant was raised in the reaction mixture, the titanium dioxide nanoparticles showed an apparently non-linear binding process. CONCLUSIONS: This work demonstrates that MALDI-TOFMS can be used for direct determination of the binding of surfactant lipids to nanoparticles and represents an important initial step towards a simple and quantitative in vitro method for assessment of interactions of nanoparticles with lung surfactants.

Rapid screening of drug compounds in urine using a combination of microextraction by packed sorbent and rotating micropillar array electrospray ionization mass spectrometry.

RATIONALE: Screening of drugs from urine samples can be non-selective or laborous, using either immunological, gas chromatography/mass spectrometry (GC/MS) or liquid chromatography (LC)/MS methods. Therefore, a rapid screening method for selected drugs in urine sample was developed in a proof-of-principle manner, utilizing simple and fast techniques for both sample treatment and sample analysis. METHODS: Sample treament of spiked urine samples was performed with microextraction by packed sorbent (MEPS). Five different sorbent materials (C(2), C(8), C(18), M1 (cation exchanger), and Sil (pure silica)) were tested for the MEPS. The sample analysis was performed using a circular microchip with 60 micropillar electrospray ionization (µPESI) tips combined with a mass spectrometer (either a triple-quadrupole or ion-trap mass spectrometer) without any chromatographic step. RESULTS: The sample treatment/analysis setup was tested using three drug compounds at a concentration of 1 µM. We found that the C(2), C(8) and C(18) sorbents in combination with 96% alkaline methanol as an eluent worked the best. All compounds were easily detected and identified by MS/MS in spiked urine samples. The whole qualitative analytical procedure was rapid as the sample treatment together with the MS analysis took about 5 min per sample. CONCLUSIONS: A rapid screening method for selected drugs from urine samples was developed, providing adequate selectivity and sensitivity, as well as a short total analysis cycle time. This new method can provide a new alternative for screening purposes, as both the extraction and analysis steps could be totally automatized.

Linking soil O2, CO2, and CH4 concentrations in a Wetland soil: implications for CO2 and CH4 fluxes.

Oxygen (O(2)) availability and diffusivity in wetlands are controlling factors for the production and consumption of both carbon dioxide (CO(2)) and methane (CH(4)) in the subsoil and thereby potential emission of these greenhouse gases to the atmosphere. To examine the linkage between high-resolution spatiotemporal trends in O(2) availability and CH(4)/CO(2) dynamics in situ, we compare high-resolution subsurface O(2) concentrations, weekly measurements of subsurface CH(4)/CO(2) concentrations and near continuous flux measurements of CO(2) and CH(4). Detailed 2-D distributions of O(2) concentrations and depth-profiles of CO(2) and CH(4) were measured in the laboratory during flooding of soil columns using a combination of planar O(2) optodes and membrane inlet mass spectrometry. Microsensors were used to assess apparent diffusivity under both field and laboratory conditions. Gas concentration profiles were analyzed with a diffusion-reaction model for quantifying production/consumption profiles of O(2), CO(2), and CH(4). In drained conditions, O(2) consumption exceeded CO(2) production, indicating CO(2) dissolution in the remaining water-filled pockets. CH(4) emissions were negligible when the oxic zone was >40 cm and CH(4) was presumably consumed below the depth of detectable O(2). In flooded conditions, O(2) was transported by other mechanisms than simple diffusion in the aqueous phase. This work demonstrates the importance of changes in near-surface apparent diffusivity, microscale O(2) dynamics, as well as gas transport via aerenchymous plants tissue on soil gas dynamics and greenhouse gas emissions following marked changes in water level.

Nebulization ionization and desorption ionization analysis of reactive organofunctionalized silanes in nanofilm products.

Three different and recently developed desorption ionization techniques, transmission-mode desorption electrospray ionization (TM-DESI), low temperature plasma (LTP) ionization and nano-assisted laser desorption ionization (NALDI), are compared with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) for the analysis of two nanofilm products (NFPs) for surface coating, which contain hydrolysates and condensates of organo-functionalized silanes. The NFPs were characterized in different states from the liquid phase to the fully formed surface film. The LTP spectra were dominated by the silanes, while the corresponding di-, tri- and tetrasiloxanes were common in ESI, APCI and TM-DESI. This indicates readily condensation of the silanes during the ESI and APCI ionization processes leading to the observed siloxanes. NALDI showed larger siloxane structures than the other techniques, indicating film formation on the NALDI target. Real-time monitoring of the film formation on a glass surface by LTP showed a decreasing abundance of the silanes, while the abundances of the di-, tri and tetrasiloxanes increased significantly within the first 100 s. LTP was superior in showing the non-reacted content of the NFPs, while ESI, APCI and TM-DESI were characterized by artefact formation of siloxanes. NALDI was ideal for showing the siloxane structures of the formed film. The applicabilities of each of the ionization techniques were examined, showing the advantage of utilizing more than one ionization technique for the analysis of reactive species.

Real-time monitoring of the progress of polymerization reactions directly on surfaces at open atmosphere by ambient mass spectrometry.

The progress of an on-surface polymerization process involving alkyl and perfluoroalkyl silanes and siloxanes was monitored in real-time via easy ambient sonic spray ionization mass spectrometry (EASI-MS). When sprayed on surfaces, the organosilicon compounds present in commercially available nanofilm products (NFPs) react by condensation to form a polymeric coating. A NFP for coating of floor materials (NFP-1) and a second NFP for coating tiles and ceramics (NFP-2) were applied to glass, filter paper or cotton surfaces and the progress of the polymerization was monitored by slowly scanning the surface. Via EASI(+)-MS monitoring, significant changes in the composition of hydrolysates and condensates of 1H,1H,2H,2H-perfluorooctyl triisopropoxysilane (NFP-1) and hexadecyl triethoxysilane (NFP-2) were observed over time. The abundances of the hydrolyzed species decreased compared with those of the non-hydrolysed species for both NFP-1 and NFP-2 and the heavier oligomers became relatively more abundant over a period of 15-20 min. A similar tendency favouring the heavier oligomers was observed via EASI(-)-MS. This work illustrates the potential of ambient mass spectrometry for the direct monitoring of polymerization reactions on surfaces.

Characterization of nanofilm spray products by mass spectrometry.

The use of nanofilm spray products (NFPs) has been associated with a number of severe cases of airway injuries; however, the causative agents are unknown. To identify possible causative agents, 10 products from three different suppliers have been analysed using two mass spectrometric methods: (1) ESI-MS and ESI-MS/MS; (2) GC-MS and GC-MS/MS. The 10 products could be classified into three groups (NFPs 1-3). NFP 1 and NFP 2 contained hydrolysates and condensates of the organo-functionalized silanes 1H,1H,2H,2H-perfluorooctyl triisopropoxysilane and hexadecyl triethoxysilane, respectively. NFP 3 contained non-ionic detergents and abrasive as active ingredients. To verify the fluorosilane solution in NFP 1, a synthetic NFP 1 was prepared by hydrolysis and condensation of 1H,1H,2H,2H-perfluorooctyl triethoxysilane. After about 1month in acidic 2-propanol substitution of the ethoxy groups with isopropoxy groups had taken place and all silane was converted to disiloxanes, trisiloxanes and tetrasiloxanes.

On-line monitoring of the dynamics of trihalomethane concentrations in a warm public swimming pool using an unsupervised membrane inlet mass spectrometry system with off-site real-time surveillance.

To study the long-term dynamics of trihalomethanes (THMs) in a warm (31-33 degrees C) public swimming pool, we built a robust membrane inlet mass spectrometer that could perform unsupervised, on-site monitoring of the concentration of these compounds with off-site, real-time surveillance. The instrument was installed in a technical room below the pool and operated continuously for more than a year practically only interrupted for filament replacements every 6-8 weeks. One to two days after a filament replacement, the instrument stabilized and kept its calibration until shortly before the next filament burnout. The on-line monitoring of THMs revealed a daily rhythm in the concentrations of chloroform and bromodichloromethane. They increased during the pool's closing hours and decreased during opening hours with the minimum concentration being approximately half of the maximum. Over the 1 year monitoring period, the variation in the maximum registered daily concentration was 30-100 microg/L for chloroform. The variation of bromodichloromethane was 5-10 microg/L, except during bursts of 1-2 days duration, where the concentration of bromodichloromethane could reach 100 microg/L. The burst in bromodichloromethane concentration was directly correlated with salt addition (sodium chloride) to the pool water for use in the pool's electrolytic in-line chlorination system. A correlation between THM removal from the pool water and the operation of a strong water jet system was also found.

Release of VOCs and particles during use of nanofilm spray products.

Here, we present emission data on VOCs and particles emitted during simulated use of four commercial nanofilm spray products (NFPs) used for making easy-to-clean or self-cleaning surfaces on floors, ceramic tiles, and windows. The aim was to characterize the emitted VOCs and to provide specific source strength data for VOCs and particles released to the airduring use of the products. Containers with NFP were mounted on a spray-stand inside a closed stainless steel chamber with no air exchange. NFPs were sprayed in amounts corresponding to 1 m2 surface toward a target plate at a distance of 35 cm. Released VOCs were measured by a combination of air sampling on Tenax TA adsorbent followed by thermal desorption GC/MS and GC/FID analysis and real time measurements using a miniature membrane inlet mass spectrometer. Particles were measured using a fast mobility particle sizer and an aerosol particle sizer. A number of VOCs were identified, including small alcohols, ketones and ethers, chlorinated acetones, a perfluorinated silane, limonene, and cyclic siloxanes. The number of generated particles was on the order of 3 x 10(8) to 2 x 10(10) particles/m3 per g sprayed NFP and were dominated by nanosize particles.

Analysis of semivolatile pharmaceuticals and pollutants in organic micro extracts using hot cell membrane inlet mass spectrometry.

This paper presents the first membrane inlet method that can be used together with field portable mass spectrometers for the analysis of semivolatile pharmaceuticals (pethidine, benzophenone, and cocaine) and environmental pollutants (terbutryne and butylated hydroxyl toluene (BHT)) dissolved in organic micro extracts. A microliter of the organic extract is simply injected into a closed hot cell membrane inlet (hc-MIMS), and an electron ionization mass spectrum of the vaporized semivolatile sample molecules can be recorded shortly thereafter. Detection limits at low picomole quantities or low/sub ng/microL concentrations in the extract are demonstrated for solutes in methanol, ethanol, acetone, and toluene. A linear correlation between analyte concentration and signal was found in the range of 1-100 ng/microL, and the relative standard deviation (RSD) was approximately 10%. As a practical example we demonstrate the detection of cocaine in extracts from dried coca leaves. The analysis of organic micro extracts using hc-MIMS represents a considerable extension of the type and complexity of analytes that can be measured using a field portable MIMS system, since it does not require special and field tedious modifications to the standard MIMS system.

Fast and direct screening of solid materials for their potential liberation of hydrophobic organic compounds using hot cell membrane inlet mass spectrometry.

We demonstrate that solid materials can be screened directly and without any pretreatment for their potential liberation of chemicals into the surroundings using a hot (150-250 degrees C) sample cell membrane inlet mass spectrometer with electron ionization. Three very different types of solids were tested: polymers (in this context regarded as a solid), tea leaves and pesticide-contaminated soil. From the polymers phthalates and other additives were liberated; from the tea leaves flavor additives and caffeine were liberated; and from the contaminated soil degradation products of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were liberated. In all cases we detected characteristic compounds directly from the untreated sample with an analytical turnover of 8-10 samples per hour. Improved selectivity of compounds penetrating the membrane was achieved either by operating the hot cell at different temperatures or by using variations in the time trend of individual ions following insertion of a piece of the solid material into the hot cell.

Method for quantification of chemicals in a pollution plume using a moving membrane-based sensor exemplified by mass spectrometry.

Quantification of a chemical concentration in a pollution plume using a moving membrane-based sensor can be problematic. In many cases, the sensor passes through the plume faster than the time necessary to reach a steady-state signal, which is often used for quantification. Since the exposure time is typically not known, quantification based upon the flow injection analysis principle is also impractical. In this paper, we present a two-dimensional calibration model, exemplified by membrane inlet mass spectrometry, in which the concentration of a chemical can be determined using a simple algorithm. The concentration is given by a calibration factor, which is multiplied by the peak height and divided by the value of a polynomial, calculated at a normalized peak width. The model is demonstrated to give good quantitative estimates of concentrations for exposure times down to approximately 1/10 of the time it takes to reach steady-state diffusion through the membrane. Although the model is demonstrated using membrane inlet mass spectrometry and detection of volatile organic chemicals, it should be generally applicable to many membrane-covered sensors.

Fast and direct screening of polyaromatic hydrocarbon (PAH)-contaminated sand using a miniaturized membrane inlet mass spectrometer (mini-MIMS).

A miniaturized membrane inlet mass spectrometer (mini-MIMS; total weight 10 kg everything included) was equipped with a small sample cell using a flat sheet silicone membrane mounted close to the ionizing region of a multipole mass spectrometer. Spiked sand samples were placed in small stainless steel vials and dropped into the heated sample cell (>150 degrees C). A hole in the vial in front of the membrane and above the sand made it possible for the polyaromatic hydrocarbon (PAH) residuals to penetrate the membrane and enter the mass spectrometer as they evaporated from the sample. Using this simple setup we were able to quantitatively (approximately 10% relative standard deviation (RSD)) detect PAHs with up to five aromatic rings and with detection limits in the low parts-per-million (ppm) range. The vial system solves one of the major difficulties in analysis of larger PAHs using a MIMS. Normally, analysis of PAHs with more than two rings is hampered by a long memory effect due to the sticking of the PAHs to the inlet system, the membrane and surfaces in the vacuum system. By removing the vial from the sample cell within 2 min, we were able to analyze samples at 5-10 min intervals. The preliminary laboratory experiments presented here show much promise with respect to the development of a hand held (<10 kg) on-site mass spectrometry system for PAH screening at contaminated sites.

Characterization of a mini membrane inlet mass spectrometer for on-site detection of contaminants in both aqueous and liquid organic samples.

A mini membrane inlet mass spectrometer (mini-MIMS) of a total weight of 12 kg was constructed using a miniature Multipole mass spectrometer, a small vacuum system and a flexible flat sheet membrane inlet, where the exposed membrane area can be changed by a factor of 80. The variable membrane area together with the possibility of operating the Multipole at pressures up to 1 x 10(-3) Torr made it possible to test the system with three microporous membranes (cellulose, polyether sulfone and polypropylene) normally not compatible with standard electron ionization MIMS systems and a standard non-porous polydimethylsiloxane membrane. We found that the hydrophilic cellulose and polyether sulfone membranes had selectivity characteristics opposite to those of the standard silicone membrane. They demonstrated preferential detection of hydrophilic compounds in hydrophobic organic solvents, whereas the silicone membrane preferentially detects hydrophobic organic compounds in aqueous solution. Using the cellulose membrane, organic contaminants and water could be detected in organic solvents at 10-100 ppm levels by weight, the relative high detection limits primarily caused by interference from a high chemical background from the solvent. When being used with the standard silicone membrane the mini-MIMS behaved just like most standard MIMS systems with detection limits of volatile organic compounds in water at concentrations just below 1 ppm. The hydrophobic microporous polypropylene membrane was not found to be useful with the mini-MIMS.

Sustained glycolytic oscillations--no need for cyanide.

Using fluorescence spectroscopy we detected long trains of macroscopic oscillations in the glycolytic pathway, in whole cell suspensions of Saccharomyces cerevisiae, without addition of cyanide. Such oscillations may be induced if argon or another inert gas is bubbled through the yeast cell suspension. This supports that the synchronizing agent is a volatile compound secreted by the yeast cells, e.g. CO2 and/or acetaldehyde. Our results show that the rate of acetaldehyde removal is not a crucial parameter to the synchronization of the yeast cells. The sample cell was connected to a membrane inlet mass spectrometer (MIMS) for online determination of extracellular non-polar compounds. Oscillations in the secretion of CO2 were detected using the MIMS.

On-line monitoring of important organoleptic methyl-branched aldehydes during batch fermentation of starter culture Staphylococcus xylosus reveal new insight into their production in a model fermentation.

A small fermentor (55 mL) was directly interfaced to a membrane inlet mass spectrometer for continuous on-line monitoring of oxygen and volatile metabolites during batch fermentations of the starter culture Staphylococcus xylosus. Using this technique, we were able to correlate production of the very important flavor compounds 2-methylbutanal, 3-methylbutanal, and 2-methylpropanal with various growth conditions. We found that the aldehydes were present in the culture broth only as transient metabolites. They were produced in the exponential growth phase, reached a maximum concentration when the culture became anaerobic, and then they rapidly disappeared from the culture medium. This general pattern was observed for three different strains of S. xylosus and S. carnosus. Small amounts of inoculum or increased exposure to oxygen were found to favor production of the aldehydes as a result of a longer aerobic growth period. Growing S. xylosus under conditions resembling those in a fermented sausage revealed that NaCl (5%) increased aldehyde production considerably, whereas KNO(3) (0.03%) or NaNO(2) (0.03%) had little effect. A lowering of pH from 7.2 to 6.0 reduced cell density, but had a minor affect on aldehyde production.

Novel pyrazine metabolites found in polymyxin biosynthesis by Paenibacillus polymyxa.

A complex mixture of methyl-branched alkyl-substituted pyrazines was found in the growth medium of the polymyxin-producing bacterium Paenibacillus polymyxa, and of these, seven are new natural compounds. A total of 19 pyrazine metabolites were identified. The dominant metabolite was 2,5-diisopropylpyrazine as identified using a combination of high-resolution mass spectrometry, (1)H- and (13)C-nuclear magnetic resonance, gas chromatography-mass spectrometry as well as co-elution with an authentic standard. Its biosynthesis was correlated with growth and production was strongly stimulated by valine supplementation. The other pyrazine metabolites, all related pyrazines with either one, two or three alkyl substituents, were identified by means of their mass spectral data and/or co-elution with authentic standards.

Determination of pentachlorophenol by negative ion chemical ionization with membrane introduction mass spectrometry.

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.