Prototype of the gas chromatograph-mass spectrometer to investigate volatile species in the lunar soil for the Luna-Resurs mission

In preparation for the Russian Luna-Resurs mission we combined our compact time-of-flight mass spectrometer (TOF-MS) with a chemical pre-separation of the species by gas chromatography (GC). Coupled measurements with both instruments were successfully performed with the prototype of the mass spectrometer and a flight-like gas chromatograph. The system was tested with two test gas mixtures, a mixture of hydrocarbons and a mixture of noble gases. Due to its capability to record mass spectra over the full mass range at once with high sensitivity and a dynamic range of up to 10(6) within 1 s, the TOF-MS system is a valuable extension of the GC analytical system. Based on the measurements with calibration gases performed with the combined GC-MS prototype and under assumption of mean characteristics for the Moon's regolith, the detection limit for volatile species in a soil sample is estimated to 2.10(-10) by mass for hydrocarbons and 2.10(-9) by mass for noble gases. (C) 2015 Elsevier Ltd. All rights reserved.

Development of the gas chromatograph – mass spectrometer to investigate volatile species in the lunar soil for the Luna-Resurs mission

Since the analysis of the lunar rocks and soil samples, brought to Earth by the Apollo missions, it is believed that the Moon has a waterless nature and also other volatile species are strongly depleted. Advancement in analysis techniques helped to identify water and other volatile species in lunar volcanic glasses. Additionally, recent lunar space missions detected water and volatile organic compounds in the region of the lunar poles where permanently shadowed craters are existing. All known lunar soil samples available on Earth come from the lunar near side, close to the equator. To verify the most recent measurement results and to enhance the knowledge of the geological history of the Moon it is of high interest to perform in situ measurements on the lunar poles. For this reason the Russian space agency, Roskosmos, developed aprogram for the scientific exploration of the lunar poles. The Gas Analysis Package (GAP) is part of the selected scientific payload aboard the Luna-Resurs Lander. This instrument uses pyrolytic cells and will apply laser spectroscopy, gas chromatography and mass spectrometry to detect and analyze volatile components trapped in the lunar soil. An existing ion optical design of a compact reflectron type time-of-flight mass spectrometer, originally built for the MEAP/P-BACE balloon mission, was chosen as a part of the GAP instrument. The scope of this thesis is the development of the interface between gas chromatography (GC) and this Neutral Gas Mass Spectrometer (NGMS) to perform coupled GC-MS measurements. In the first part of this thesis the interfacing concept was developed and verified by coupling the NGMS prototype to gas chromatography. The second part of this thesis is devoted to the development of the NGMS flight version.

Identification of corona discharge-induced SF6 oxidation mechanisms using SF6/18O2/H216O and SF6/16O2/H218O gas mixtures

The absolute yields of gaseous oxyfluorides SOF2, SO2F2, and SOF4 from negative, point-plane corona discharges in pressurized gas mixtures of SF6 with O2 and H2O enriched with18O2 and H2 18O have been measured using a gas chromatograph-mass spectrometer. The predominant SF6 oxidation mechanisms have been revealed from a determination of the relative18O and16O isotope content of the observed oxyfluoride by-product. The results are consistent with previously proposed production mechanisms and indicate that SOF2 and SO2F2 derive oxygen predominantly from H2O and O2, respectively, in slow, gas-phase reactions involving SF4, SF3, and SF2 that occur outside of the discharge region. The species SOF4 derives oxygen from both H2O and O2 through fast reactions in the active discharge region involving free radicals or ions such as OH and O, with SF5 and SF4.

Analysis of in-cylinder hydrocarbons in a multi-cylinder gasoline HCCI engine using gas chromatography

Gasoline Homogeneous Charge Compression Ignition (HCCI) combustion has been studied widely in the past decade. However, in HCCI engines using negative valve overlap (NVO), there is still uncertainty as to whether the effect of pilot injection during NVO on the start of combustion is primarily due to heat release of the pilot fuel during NVO or whether it is due to pilot fuel reformation. This paper presents data taken on a 4-cylinder gasoline direct injection, spark ignition/HCCI engine with a dual cam system, capable of recompressing residual gas. Engine in-cylinder samples are extracted at various points during the engine cycle through a high-speed sampling system and directly analysed with a gas chromatograph and flame ionisation detector. Engine parameter sweeps are performed for different pilot injection timings and quantities at a medium load point. Results show that for lean engine running conditions, earlier pilot injection timing leads to partial oxidation of the injected pilot fuel during NVO, while the fraction of light hydrocarbons remains constant for all parameter variations investigated. The same applies for a variation in pilot fuel amount. Thus there is evidence that in lean conditions, pilot injection-related NVO effects are dominated by heat release rather than fuel reformation. © 2009 SAE International.

On-line introduction of high-pressure gas-liquid sample for capillary gas chromatographic analysis

An on-line sample introduction technique in capillary gas chromatograph (CGC) for the analysis of high-pressure gas-liquid mixtures has been designed and evaluated. A sample loop of 0.05 muL and a washing solvent loop of 0.5 muL are mounted on a 10-port switching valve, which serves as the injection valve. A capillary resistor was connected to the vent of sample loop in order to maintain the pressure of the sample. Both the sample and the washing solvent are transferred into the split-injection port through a narrow bore fused silica capillary inserted into the injection liner through a septum. The volume of the liner is used both as the pressure-release damper and evaporation chamber of the sample. On-line analysis of both reactants and resultants in ethylene olimer reaction mixture at 5 MPa was carried out, which demonstrated the applicability of the technique. (C) 2004 Elsevier B.V. All rights reserved.

Hollow-fiber liquid-phase microextraction and gas chromatography-mass spectrometry of barbiturates in whole blood samples

Here, we present a method for measuring barbiturates (butalbital, secobarbital, pentobarbital, and phenobarbital) in whole blood samples. To accomplish these measurements, analytes were extracted by means of hollow-fiber liquid-phase microextraction in the three-phase mode. Hollow-fiber pores were filled with decanol, and a solution of sodium hydroxide (pH 13) was introduced into the lumen of the fiber (acceptor phase). The fiber was submersed in the acidified blood sample, and the system was subjected to an ultrasonic bath. After a 5 min extraction, the acceptor phase was withdrawn from the fiber and dried under a nitrogen stream. The residue was reconstituted with ethyl acetate and trimethylanilinium hydroxide. An aliquot of 1.0 mu L of this solution was injected into the gas chromatograph/mass spectrometer, with the derivatization reaction occurring in the hot injector port (flash methylation). The method proved to be simple and rapid, and only a small amount of organic solvent (decanol) was needed for extraction. The detection limit was 0.5 mu g/mL for all the analyzed barbiturates. The calibration curves were linear over the specified range (1.0 to 10.0 mu g/mL). This method was successfully applied to postmortem samples (heart blood and femoral blood) collected from three deceased persons previously exposed to barbiturates.

Gas hydrates at DSDP Leg 84

On DSDP Leg 84, gas hydrates were found at three sites (565, 568, and 570) and were inferred, on the basis of inorganic and organic geochemical evidence, to be present at two sites (566 and 569); no evidence for gas hydrates was observed at Site 567. Recovered gas hydrates appeared as solid pieces of white, icelike material occupying fractures in mudstone or as coarse-grained sediment in which the pore space exhibited rapid outgassing. Also a 1.05-m-long core of massive gas hydrate was obtained at Site 570. Downhole logging indicated that this hydrate was actually 3 to 4 m thick. Measurements of the amount of methane released during the decomposition of these recovered samples clearly showed that gas hydrates had been found. The distribution of evolved hydrocarbon gases indicated that Structure I gas hydrates were present because of the apparent inclusion of methane and ethane and exclusion of propane and higher molecular weight gases. The water composing the gas hydrates was fresh, having chlorinities ranging from 0.5 to 3.2 per mil. At Sites 565, 568, and 570, where gas hydrates were observed, the chlorinity of pore water squeezed from the sediment decreased with sediment depth. The chlorinity profiles may indicate that gas hydrates can often occur finely dispersed in sediments but that these gas hydrates are not recovered because they do not survive the drilling and recovery process. Methane in the gas hydrates found on Leg 84 was mainly derived in situ by biogenic processes, whereas the accompanying small amounts of ethane likely resulted from low-temperature diagenetic processes. Finding gas hydrates on Leg 84 expands observations made earlier on Leg 66 and particularly Leg 67. The results of all of these legs show that gas hydrates are common in landward slope sediments of the Middle American Trench from Mexico to Costa Rica.

Various ratios of C1-C5 hydrocarbons, gas composition and computed temperature at DSDP Leg 64 Holes

I have evaluated shipboard data and preliminary interpretations related to organic geochemistry in light of additional shore-based analyses. Data on interstitial gas, the C/N ratio, and fluorescence indicate that organic matter was altered by sills and that these were all single intrusions except the upper sill complex at Site 481, which was a multiple emplacement. Site 477 had the highest in situ temperature, estimated from interstitial gas composition to be 225°C.

Development of a novel pyrolysis-gas chromatography/mass spectrometry method for the analysis of poly(lactic acid) thermal degradation products

Thermal degradation of PLA is a complex process since it comprises many simultaneous reactions. The use of analytical techniques, such as differential scanning calorimetry (DSC) and thermogravimetry (TGA), yields useful information but a more sensitive analytical technique would be necessary to identify and quantify the PLA degradation products. In this work the thermal degradation of PLA at high temperatures was studied by using a pyrolyzer coupled to a gas chromatograph with mass spectrometry detection (Py-GC/MS). Pyrolysis conditions (temperature and time) were optimized in order to obtain an adequate chromatographic separation of the compounds formed during heating. The best resolution of chromatographic peaks was obtained by pyrolyzing the material from room temperature to 600 °C during 0.5 s. These conditions allowed identifying and quantifying the major compounds produced during the PLA thermal degradation in inert atmosphere. The strategy followed to select these operation parameters was by using sequential pyrolysis based on the adaptation of mathematical models. By application of this strategy it was demonstrated that PLA is degraded at high temperatures by following a non-linear behaviour. The application of logistic and Boltzmann models leads to good fittings to the experimental results, despite the Boltzmann model provided the best approach to calculate the time at which 50% of PLA was degraded. In conclusion, the Boltzmann method can be applied as a tool for simulating the PLA thermal degradation.