An Apparatus for Measurement of Carbonate

The phase reaction conversion (PRC) headspace gas chromatographic (HSGC) technique was employed to develop a method for the determination of the content of carboxyl groups in wood fibers. Treatment of the wood fibers using hydrochloric acid was applied to convert carboxyl groups to carboxyl acids. Bicarbonate solution was then used to react with carboxyl acids on the treated fibers in the headspace of a testing vial to form carbon dioxide that was analyzed by a thermal conductivity detector using gas chromatography. The conversion reaction was conducted at 60 °C for about 10 min to achieve near complete conversion. The contribution to the GC detector signal from carbon dioxide formed by residual hydrochloric acid on wood fibers can be accounted for by the known experimental parameters. The effect of carbon dioxide in the headspace of the testing vial air was calibrated or can be eliminated by purging the testing vial using nitrogen before conducting experiment. The measured contents of carboxyl groups in eight wood fiber samples were in good agreement with those measured by a titration method. The present method is accurate, rapid, and automated.

A method has been developed to analyze headspace oxygen, nitrogen, and carbon dioxide in a variety of beverages and packages. A package is punctured with a specialized sampler. The headspace gases flow into an evacuated gas sampling valve. The gases are automatically switched onto a gas chromatographic column where they are separated and then detected using a thermal conductivity detector. The peak areas of the headspace gases are compared to those of calibration gases to determine the quantity of each gas present. Gases may be determined at concentrations as low as 150 ppm v/v (0.002 psia; 20.5°C) for oxygen and up to 100% v/v (70 psia; 20.5°C) for carbon dioxide. After calibration, the time for duplicate analysis of all three gases is 11.0 min. The procedure has been used to study nitrogen purging in cans, antioxidant effects in juices, headspace oxygen in aseptic packages, wine headspace composition, permeation through synthetic corks, and beverage carbonation corrected for the effect of headspace oxygen and nitrogen.

Determination of acidic and basic species by headspace gas chromatography

This paper reports on the effect of flow rate of helium (He) carrier gas on the key parameters of gas chromatography equipped with thermal conductivity detector (GC-TCD) for the measurement of carbon dioxide (CO2 ), propane (C3H8) and carbon monoxide (CO) in gravimetric standard gas mixture (Grav-SGM). The carrier gas has a function to transport vaporized molecules through the column during the GC separation process. The study provides opportunity to experimentally investigate the effect of gas flow rate on the several key parameters of the GC-TCD including retention time, peak area, peak height, response factor, resolution and selectivity. The results show that all key parameters were found to be carrier gas flow rate dependent. The increase of the gas flow rate could significantly decrease the retention time, peak area and response factor of the gas components. While both resolution and selectivity factor were observed to have a substantial decrease with increasing the flow rate of carrier gas. Therefore, proper selection of flow rate level of carrier gas is suggested before a GC measurement is carried out for obtaining an optimum condition.

A novel method for the determination of oxalate content in food is developed using headspace gas chromatographic (HS-GC) technology. This method is based on the reaction between oxalate and sodium bromate in an acidic medium, in which oxalate is converted to carbon dioxide that is measured by GC with a thermal conductive detector. It was found that a complete conversion of oxalate to carbon dioxide can be achieved at a temperature of 70 °C within 4 minutes. The optimal reaction conditions obtained in the present work also minimize the side reactions caused by interfering species, such as organic acid and alcohols, with sodium bromate. The present method is simple, rapid, accurate, and very suitable for use in quantification of oxalate content in food.

Efficient production of solar fuels is an imperative for meeting future fossil-fuel-free energy demands. Hydrogen that is derived from the splitting of water by solar energy is clearly attractive as a clean energy vector, and there have been many attempts to construct viable molecular and biomolecular devices for photohydrogen production. A common approach in the construction of such devices is the utilization of tris(bipyridine)ruthenium, zinc porphyrin, or related molecular materials as photosensitizers in conjunction with a tethered or free electrocatalyst or enzymic system. Apart from cost, such systems suffer from having limited lifetimes, which may be attributed at least in part to the intrinsic reactivity of the organic N-donor ligands in the radical anion form of the photoexcited state and photodegradation pathways.

An efficient technique was developed to monitor the emission of hydrogen and carbon dioxide from bacteria cultures by headspace gas chromatography and to investigate the efficacy of chemical antibiotics and of natural compounds with antimicrobial properties. Facultative anaerobes emit hydrogen and carbon dioxide from cultures in the closed headspace vials and obligate anaerobes too, if the air above the cultures in the vials is replaced by nitrogen. Antibiotics added to the sample cultures are apparently effective if the emission of hydrogen and carbon dioxide is suppressed. If not, either they are ineffective or the related bacteria are even resistant. The headspace technique can detect bacterial contamination in various samples, and examples are presented for food purchased from supermarkets and for medical specimens, including recognition of antibiotic resistance. However, the described technique cannot identify the related bacteria at a species or genus level, but is well suited for example for screening the bulk of food in supermarkets for microbe contamination or for the search of natural antibiotics. The samples are incubated with the proper nutrient medium in closed septum vials which remain closed during the whole process. The personnel in the lab never come into contact with pathogens, and thus, safety regulations are warranted. The described technique can be carried out with all commercially available gas chromatographs, even including simple low-cost instruments, equipped with a standard packed column and a thermal conductivity detector, up to expensive and fully automated instruments, such as used for forensic blood alcohol analysis.

This document describes and implements the process to establish the concentration of flammable gas/volatile organic compounds (VOCs), hydrogen, and methane in a waste container intended for shipment in the Transuranic Package Transporter-II (TRUPACT-II) or HalfPACT packagings. An aliquot of headspace gas (HSG) is sampled from a waste container and analyzed using one analytical unit which is a gas chromatograph (GC) with two detectors, a mass spectrometer (MS) and a thermal conductivity detector (TCD). The sample introduced to the GC is split and part goes to MS and the other part goes to TCD. The MS analyzes sample for volatile organic compounds (VOC) and the TCD analyzes for hydrogen and methane. The requirements and technical bases for allowable flammable gas/VOC concentrations are described in the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC).

This document describes and implements the process to establish the concentration of flammable gas/volatile organic compounds (VOCs), hydrogen, and methane in a waste container intended for shipment in the Transuranic Package Transporter-II (TRUPACT-II) or HalfPACT packagings. An aliquot of headspace gas (HSG) is sampled from a waste container and analyzed using one analytical unit which is a gas chromatograph (GC) with two detectors, a mass spectrometer (MS) and a thermal conductivity detector (TCD). The sample introduced to the GC is split and part goes to MS and the other part goes to TCD. The MS analyzes sample for volatile organic compounds (VOC) and the TCD analyzes for hydrogen and methane. The requirements and technical bases for allowable flammable gas/VOC concentrations are described in the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC).

This document describes and implements the process to establish the concentration of flammable gas/volatile organic compounds (VOCs), hydrogen, and methane in a waste container intended for shipment in the Transuranic Package Transporter-II (TRUPACT-II) or HalfPACT packagings. An aliquot of headspace gas (HSG) is sampled from a waste container and analyzed using one analytical unit which is a gas chromatograph (GC) with two detectors, a mass spectrometer (MS) and a thermal conductivity detector (TCD). The sample introduced to the GC is split and part goes to MS and the other part goes to TCD. The MS analyzes sample for volatile organic compounds (VOC) and the TCD analyzes for hydrogen and methane. The requirements and technical bases for allowable flammable gas/VOC concentrations are described in the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC).

This document describes and implements the process to establish the concentration of flammable gas/volatile organic compounds (VOCs), hydrogen, and methane in a waste container intended for shipment in the Transuranic Package Transporter-II (TRUPACT-II) or HalfPACT packagings. An aliquot of headspace gas (HSG) is sampled from a waste container and analyzed using one analytical unit which is a gas chromatograph (GC) with two detectors, a mass spectrometer (MS) and a thermal conductivity detector (TCD). The sample introduced to the GC is split and part goes to MS and the other part goes to TCD. The MS analyzes sample for volatile organic compounds (VOC) and the TCD analyzes for hydrogen and methane. The requirements and technical bases for allowable flammable gas/VOC concentrations are described in the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC).

This document describes and implements the process to establish the concentration of flammable gas/volatile organic compounds (VOCs), hydrogen, and methane in a waste container intended for shipment in the Transuranic Package Transporter-II (TRUPACT-II) or HalfPACT packagings. An aliquot of headspace gas (HSG) is sampled from a waste container and analyzed using one analytical unit which is a gas chromatograph (GC) with two detectors, a mass spectrometer (MS) and a thermal conductivity detector (TCD). The sample introduced to the GC is split and part goes to MS and the other part goes to TCD. The MS analyzes sample for volatile organic compounds (VOC) and the TCD analyzes for hydrogen and methane. The requirements and technical bases for allowable flammable gas/VOC concentrations are described in the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC).

This document describes and implements the process to establish the concentration of flammable gas/volatile organic compounds (VOCs), hydrogen, and methane in a waste container intended for shipment in the Transuranic Package Transporter-II (TRUPACT-II) or HalfPACT packagings. An aliquot of headspace gas (HSG) is sampled from a waste container and analyzed using one analytical unit which is a gas chromatograph (GC) with two detectors, a mass spectrometer (MS) and a thermal conductivity detector (TCD). The sample introduced to the GC is split and part goes to MS and the other part goes to TCD. The MS analyzes sample for volatile organic compounds (VOC) and the TCD analyzes for hydrogen and methane. The requirements and technical bases for allowable flammable gas/VOC concentrations are described in the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC).

This document describes and implements the process to establish the concentration of flammable gas/volatile organic compounds (VOCs), hydrogen, and methane in a waste container intended for shipment in the Transuranic Package Transporter-II (TRUPACT-II) or HalfPACT packagings. An aliquot of headspace gas (HSG) is sampled from a waste container and analyzed using one analytical unit which is a gas chromatograph (GC) with two detectors, a mass spectrometer (MS) and a thermal conductivity detector (TCD). The sample introduced to the GC is split and part goes to MS and the other part goes to TCD. The MS analyzes sample for volatile organic compounds (VOC) and the TCD analyzes for hydrogen and methane. The requirements and technical bases for allowable flammable gas/VOC concentrations are described in the Contact-Handled Transuranic Waste Authorized Methods for Payload Control (CH-TRAMPAC).

Among the various methods available for reduction of CO2, the electrochemical reduction method stands out due to it being capable of producing industrially important fuels, organic chemicals and pure oxygen. Such process takes place in an electrochemical cell, where carbon dioxide is reduced to at room temperature and atmospheric pressure, using only water, carbon dioxide and electricity at specific electrochemical potentials. Here, electrocatalysts have an important role to play, for enhancing the kinetics of the process and also for rendering the formation of desired products feasible at some selected potentials. In the present research, we are exploring the usage of La-based transition metal (TM) oxides, crystallizing in perovskite structure, as electrocatalysts. The synthesis of these metal oxides is cost effective and tuning the performance via doping is facile. Furthermore, these perovskites are stable in stoichiometric, as well as non-stoichiometric, forms and due to the basicity of La exhibits affinity for CO2. Accordingly, here we have investigated the efficiency and effectiveness of different La-based TM oxides, as electrocatalysts, towards the formation of industrially relevant products upon reduction of CO2. It may be mentioned here that, in order to enhance the efficiency of the electrocatalysts, as well as the mass transport of CO2 to the surface of the electrocatalysts, we have designed a new electrolysis cell where gas diffusion electrode (GDE) containing the electrocatalysts is used as working electrode. All the La-based TM oxides (i.e., LaCoO3, LaCrO3, LaFeO3, LaMnO3, LaNiO3) were synthesized via citrate solution-combustion route and calcined in air atmosphere at 850 oC for 6 h, with the heating rate being 10 oC/minute. Phase evolution of the TM oxides before and after usage, as electrocatalysts, were checked using X-ray diffraction (XRD; EMPYREAN PANalytical diffractometer) having Cu Kα radiation and scanning at a rate of 1 o/min between 10 to 90o. Inorganic Crystal Structure Database was used for the phase analysis of the powder catalysts. The composition of the perovskite catalysts (in terms of the ratios of the metals) were quantitatively analyzed by energy dispersive spectroscopy (EDS; QUANTA 200). Morphologies of the oxide particles were observed using scanning electron microscopy (SEM) JEOL JSM-7600F. The specific surface area of the perovskite catalysts were measured via BET using Micromeritics 3 FLEX Surface Characterization. The electrochemical CO2 reduction reaction was performed in an electrolysis cell via chronoamperometry using Biologic potentiostat (Model VSP 300). The reduction reactions were carried out on gas diffusion electrode (GDE) using basic aqueous electrolyte. The applied potentials were -1.1 V, -1.3 V, -1.5 V, -1.7 V, -1.9 V and -2.1 V vs. Hg/HgO, as reference electrode. The chronoamperometry experiments were performed for 3 h at each potential. The current densities obtained during the electrochemical CO2 reduction experiments were obtained for all the La-based TM oxide electrocatalysts used, viz., LaCoO3, LaCrO3, LaFeO3, LaMnO3, LaNiO3. The liquid products present in the electrolyte after the experiments were analyzed by high performance liquid chromatography (HPLC) using Agilent 1260 infinity series model with Aminex HPX-87H column. The gaseous products were analyzed by gas chromatography - thermal conductivity detector (GC-TCD) using Nucon 5700 gas chromatography. XRD scans recorded with the as-synthesized and calcined La-based TM oxides indicate that the oxides were phase pure (as shown in Fig. 1). The crystal structure was established as perovskite. The composition of the as-synthesized and calcined perovskite electrocatalysts, as determined using EDS, were in good agreement with the target compositions. The current densities were fairly stable during the 3 h long experiments for all the potentials studied; with an example being shown in Fig. 2. All the electrocatalysts produced formate (HCOO-), acetate (CH3COO-) and hydrogen as the products of electrochemical CO2 reduction. Furthermore, ethanol (C2H5OH) and 1-propanol (C3H7OH) were also formed on LaCoO3, with LaMnO3 being able to produce 1-propanol (C3H7OH) as one of the products. Hence, as per the present set of results in the context of the formation of desired products, LaCoO3 and LaMnO3 seem to be more promising among the La-TM-oxide electrocatalysts studied here. Keywords: CO2 reduction, transition metal oxide, electrocatalyst, chronoamperometry, reaction product. Figure 1