Volatile Inorganic Compounds Research Articles

Small-Scale Study of Siberian Biomass Burning: I. Smoke Microstructure

Reliable assessment of the impact of Siberian boreal forest wildfires on the environment and climate necessitates an improved understanding of microphysical and chemical properties of emitted aerosols. Smoldering, flaming and mixed fires of typical Siberian biomass (pine and debris) were simulated during a small-scale study in a Large Aerosol Chamber (LAC). Individual particle analysis of PM_(10) and PM_(2.5) smoke morphology and elemental composition revealed a strong dependence on combustion temperature, i.e., a dominant abundance of soot agglomerates versus roughly spherical organic particles in the flaming and smoldering phase, respectively. Cluster analysis of smoke microstructure was used to apportion the emitted particles into major characteristic groups: Soot and Organic, which accounted for around 90% and 60% of total particle numbers emitted from the flaming and smoldering fires, respectively. Carbon fractions and inorganic ion analysis supported the identification of particle types representative of combustion phase and biomass type. Elemental carbon (EC) particles from flaming fires comprised approximately 25% of Group Soot, in good agreement with a high EC fraction in total carbon of around 65% and low organic carbon (OC)/EC ratio near 0.5. Smoldering fires of pine and debris produced exclusively organic particles with high OC/EC ratios of 194 and 34, respectively. Small quantities of elemental constituents in biomass were vaporized during combustion and produced internally/externally mixed fly ash in Group Ca-, Si-, and Fe-rich of significantly less abundance. Ca, Cl, S, and Mg were more frequently distributed elements in pine than debris smoke. Sulfates and nitrates produced from gas-to-particle reactions formed Group S- and N-rich. During time evolution of smoke volatile inorganic compounds were condensed as potassium chlorides and sulfates into a newly formed Group K,Cl-rich. Quantification of Siberian biomass smoke microstructure by chemical micromarkers enables aerosols to be classified with respect to a source type assigned to Siberian wildfires.

Tar Variability in the Producer Gas in a Bubbling Fluidized Bed Gasification System

Previous studies in an atmospheric bubbling fluidized bed (BFB) gasification system indicated significant tar variability along the system. In this paper, the experimental procedure has been improved for reliable results and understanding of tar variability in the producer gas. By introducing a new sample point for tar analysis to the system, experiments indicated tar reduction in the gasifier, probably due to continuous accumulation of char and ash in the bed, as well as in the ceramic filter because of thermo- and catalytic effects. Thermogravimetric analysis of the filter sample indicated 14% of volatile inorganic compounds, and additional analysis of inorganic parts showed alkali and alkaline earth metal content, well-known as tar breakdown catalysts.

Measurement of organic mass to organic carbon ratio in ambient aerosol samples using a gravimetric technique in combination with chemical analysis

Organic materials make up a significant fraction of ambient particulate mass. It is important to quantify their contributions to the total aerosol mass for the identification of aerosol sources and subsequently formulating effective control measures. The organic carbon (OC) mass can be determined by an aerosol carbon analyzer; however, there is no direct method for the determination of the mass of organic compounds, which also contain N, H, and O atoms in addition to C. The often-adopted approach is to estimate the organic mass (OM) from OC multiplying by a factor. However, this OC-to-OM multiplier was rarely measured for a lack of appropriate methods for OM. We report here a top-down approach to determine OM by coupling thermal gravimetric and chemical analyses. OM is taken to be the mass difference of a filter before and after heating at 550 °C in air for 4 h minus mass losses due to elemental carbon (EC), volatile inorganic compounds (e.g., NH 4NO 3), and loss of aerosol-associated water that arise from the heating treatment. The losses of EC and inorganic compounds are determined through chemical analysis of the filter before and after the heating treatment. We analyzed 37 ambient aerosol samples collected in Hong Kong during the winter of 2003, spring of 2004, and summer of 2005. A value of 2.1±0.3 was found to be the appropriate factor to convert OC to OM in these Hong Kong aerosol samples. If the dominant air mass is classified into two categories, then an OM-to-OC ratio of 2.2 was applicable to aerosols dominated by continent-originated air mass, and 1.9 was applicable to aerosols dominated by marine air mass.

Evaluation of solid sampling-electrothermal vaporization-inductively coupled plasma mass spectrometry and solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of Cr in various materials using solution-based calibration approaches

In this work, the possibilities for the direct determination of Cr in solid samples by means of graphite furnace atomic absorption spectrometry (SS-GFAAS) and by means of electrothermal vaporization-inductively coupled plasma mass spectrometry (SS-ETV-ICPMS) have been critically evaluated and compared, the goal always being to develop simple and fast methods, only relying on the use of aqueous standards for calibration. Four reference materials of very different nature (milk powder, lobster hepatopancreas, polyethylene and sewage sludge), covering a wide Cr concentration range (from 17.7 ng g−1 to 37.2 µg g−1), were selected for the study. The diverse volatility of their matrixes, compared with that of Cr, resulted in different degrees of difficulty for both techniques. SS-GFAAS offers a better limit of detection (2 ng g−1) than SS-ETV-ICPMS (30 ng g−1), mainly due to the occurrence of C-based polyatomic interferences with the latter technique. The samples that presented the least difficulties were those for which the matrix is mainly of an organic nature and can be easily removed during the pyrolysis step, allowing a selective atomization/vaporization of the analyte. Under these circumstances, external calibration against aqueous standards was feasible for SS-GFAAS in all cases. SS-ETV-ICPMS proved to be more sensitive to matrix effects, but the use of the palladium (added for its carrier properties) signal as internal standard also allowed the use of this straightforward calibration procedure. On the other hand, the analysis of sewage sludge (containing 85% of hardly volatile inorganic compounds) represented the most complicated situation for both techniques: for SS-GFAAS, the addition of Na2CO3 to effect an in-situ microfusion of the sample during the pyrolysis step greatly helped to improve the situation, while for SS-ETV-ICPMS the single standard addition method was necessary. In all cases, a good agreement with the certified values was obtained. The precision ranged between 6 and 22% relative standard deviation, depending on the homogeneity and the sample mass used. These values could be further improved, if needed, by increasing the number of replicates per determination (usually five). Every determination required approximately 15–20 min, except when the single standard addition method was used (30–40 min). Therefore, it can be stated that both techniques show the capability of providing a direct determination of this analyte in a variety of samples, at very different concentration levels, allowing the development of fast and reliable solid sampling procedures.

What can we expect from the in situ chemical investigation of a cometary nucleus by gas chromatography: First results from laboratory studies

Comets are probably the most primitive bodies of the solar system, and they participated in the early bombardment of the primitive planets. Consequently, the knowledge of their composition can play a key role in our understanding of the solar system formation, the origin of the planetary volatile constituents, and the origin of the organics implied in terrestrial prebiotic chemistry. However, we still do not have any direct information about the molecular composition of the cometary nucleus. This is why the COmetary SAmpling and Composition experiment (COSAC), onboard the surface landing probe of the Rosetta cometary mission, is specifically devoted to the molecular and enantiomeric analysis of a cometary nucleus. This experiment includes a gas chromatograph instrument dedicated to the specific identification and quantification of the general molecular species present in samples collected at the nucleus surface. In order to evaluate the performances of the integrated chromatographic system which was selected for the flight model instrument, experiments were carried out with a laboratory set up that reproduced the flight configuration and mimicked the in situ operating conditions. The obtained results demonstrate the ability for the gas chromatograph to identify a wide range of organic and inorganic volatile compounds, even those present at trace level, within the constrained space operating conditions. The aim of this paper is to present, for the first time, the performances of this system and to discuss the potential role of in situ gas chromatographic measurements in the future cometary, planetological and prebiotic chemistry studies.

SPECIES ANALYSIS OF INORGANIC COMPOUNDS IN WORKROOM AIR BY ATOMIC SPECTROSCOPY

Sampling methods for the determination of volatile inorganic compounds in workroom air are described. The main factor affecting the adsorption capacity of activated charcoal for iron pentacarbonyl is air flow rate. Nickel tetracarbonyl is collected quantitatively at flow rates of up to 1l/min if the volume of air sampled does not exceed 1001. Arsine, phosphine and stibine are collected quantitatively from air by use of a double filter air cassette Silver nitrate impregnated backing pads are shown to trap the hydrides with better than 99.9% efficiency. Several atomic spectroscopic methods have been applied to the determination of these volatile species, with electrothermal atomic absorption and inductively coupled plasma atomic emission spectroscopy being preferred. Concentrations of the hydrides in various workroom atmospheres were found to be well below the Threshold Limit Values.

Plasma sources in inorganic-gas analysis (review)

A traditional line in inorganic-gas spectral analysis is based on using the emission from atoms and molecules on plasma excitation; the first paper on the topic was published almost a hundred years ago [I]. Originally, plasma sources were used only to determine gaseous impurities in air and certain simple gases: hydrogen, oxygen, nitrogen, helium, neon, and argon. More recently, they have been used for determining volatile inorganic compounds (hydrides, halides, oxides, and so on) either as impurities in pure gases or in complicated technological mixtures. The methods here form two groups: for binary or pseudobinary gas mixtures and for complex ones. In the first, there are methods in which there are no effects on the signal from the undetermined impurities, and the calibration curves uniquely reflect the relation between the contents for the test and major components. In the second, there are methods where the variations in the contents of undetermined or third components have substantial effects. This classification or third components have substantial effects. This classification differs from the traditional one, where methods are distinguished by purpose (pure gases and complex mixtures), but it seems justified because it is based on the plasma processes. Binary (Pseudobinary) Mixtures. Topics here have mainly been dealt with in [2] and in certain later papers [3-7], so here we nlerely briefly discuss the major results given in Tables 1 and 2 for three lines: determining components difficult to excite, determining ones readily excited, and analyzing molecular-gas mixtures having similar excitation potentials. The most sensitive form of spectral analysis concerns determining readily excited trace components in major ones difficult to excite, where the qualitative composition determines where Cs the detection limit, falls in the range from 10 -2 to i0 -s mol.% (I in Table i). The best results here are from exciting the spectrum in a high-frequency discharge in flowing gas in a tube i-2 mm in diameter near atmospheric pressure [3-5]. The random error as a rule does not exceed 5-10% relative but rises to 30% relative at the lower limit. Determining trace components difficult to excite in readily excited matrices. The scope for spectral analysis here is somewhat limited. The detection limits are usually no better than 10 -I mol.%, but the best results (II in Table I) have been obtained at low pressures (P ~ 1 kPa) in flowing gases with discharge tubes not more than i mm in diameter. Analyzing mixtures of molecular gases having comparable excitation potentials. Table 2 shows the scope here; as in the previous case, the detection limits are comparatively poor. There is a fairly simple method of lowering the detection limits: diluting the mixture by about a factor of 100 with pure helium , which sometimes increases the spectrum intensi~y bya factor of 5-10 [8]. There is usually no advantage from further dilution with helium, firstly because the intensity falls because the analytical species is reduced in concentration and secondly because impurities in the diluting gas begin to have an effect.

Gas‐Phase‐Functionalized Plasma‐Developed Resists:Initial Concepts and Results for Electron‐Beam Exposure

A resist method involving gas phase functionalization of exposed or unexposed resist by volatile inorganic compounds followed by pattern development using oxygen reactive ion etching is described for use in ion, photo, electron, and x‐ray lithography. Negative or positive tones can be obtained in theory from a single exposure by employing selective reaction of either the exposed or unexposed regions with volatile reactive inorganic compounds that form in situmasks during plasma development (usually as refractory metal oxides). Near surface functionalization (top several thousand angstroms) is seen as having resolution advantages for electron and photolithography. It is envisioned as being controlled by either limited permeation or by selective near‐surface exposure (i. e., low voltage ion or electron exposures). In electron lithography, this could reduce the proximity effect in backscatter‐limited thick resist films on high Z substrates. Consequently, we have studied materials and functionalizing reagents for electron lithography at 10 keV. The radiation‐initiated reactions studied in the resist were the creation and destruction of unsaturation (olefins, etc.). The inorganic functionalizing reagent was diborane. Pattern development was achieved using reactive ion etching. Thin (≤2000Aå) 1 μm line and space patterns were obtained at 10–50 μC/cm2 doses for materials which afforded negative and positive tones. These include chlorinated polyacrylates, polyisoprene, and copolymers containing unsaturation and chlorine functionality.

The search for organic substances and inorganic volatile compounds in the surface of Mars

A total of four Martian samples, one surface and one subsurface sample at each of the two Viking landing sites, Chryse Planitia and Utopia Planitia, have been analyzed for organic compounds by a gas chromatograph-mass spectrometer. In none of these experiments could organic material of Martian origin be detected at detection limits generally of the order of parts per billion and for a few substances closer to parts per million. The evolution of water and carbon dioxide, but not of other inorganic gases, was observed upon heating the sample to temperatures of up to 500 C. The absence of organic compounds seems to preclude their production on the planet at rates that exceed the rate of their destruction. It also makes it unlikely that living systems that behave in a manner similar to terrestrial biota exist, at least at the two Viking landing sites.

Search for Organic and Volatile Inorganic Compounds in Two Surface Samples from the Chryse Planitia Region of Mars

Two surface samples collected from the Chryse Planitia region of Mars were heated to temperatures up to 500 degrees C, and the volatiles that they evolved were analyzed with a gas chromatograph-mass spectrometer. Only water and carbon dioxide were detected. This implies that organic compounds have not accumulated to the extent that individual components could be detected at levels of a few parts in 10(9) by weight in our samples. Proposed mechanisms for the accumulation and destruction of organic compounds are discussed in the light of this limit.

Gas Chromatography – Mass Spectroscopy Interfacial Systems

Summary Combination GC-MS interfacial systems have now been developed to a stage where it is possible to transfer the components of complex mixtures unchanged and without loss in GC resolution. It would, however, appear that no one separator is completely satisfactory for all applications, particularly if the solutes under examination are of low molecular weight and present in submicrogram quantities. In the author's opinion the following three interfaces would satisfy all possible requirements: 1. Palladium separator – specifically for low-molecular-weight volatile inorganic compounds and compounds that would not be reduced by the presence of active hydrogen. 2. Micro silicone rubber membrane separator for organic compounds up to a molecular weight of 250. 3. Jet separator – single-stage (variable) or double-stage, dependent on carrier-gas flow rate, for molecular weights from 100 upwards.