Gas Sampling Bags Research Articles

An effective technique for the storage of short lived radioactive gaseous waste

An effective technique is described to deal with volatile, short lived radioactive waste generated as a result of the routinely produced positron emission tomography (PET) radiopharmaceutical 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG). All radioactive gases and aerosols created during the synthesis are collected and stored safely in commercially available TEDLAR gas sampling bags. Once these collected PET by-products decay, the TEDLAR gas bags can be easily emptied and reused. This improved technique is effective, safe, reliable and economical.

Comparison of Gas Sampling Bags to Temporarily Store Hydrogen Sulfide, Ammonia, and Greenhouse Gases

The National Air Emission Monitoring Study (NAEMS) project measured gas concentrations using automated semi-continuous gas analyzers. An alternative gas sampling technique is to use portable systems to fill 50 L gas sample bags over 24 h sampling periods and measure gas concentrations later in the laboratory. For this technique, a gas sampling bag that can retain gases over 24 h is needed. The objective of the study was to assess the impact of initial gas concentrations (low, medium, and high) and storage times (2, 6, 12, 24, 36, 48 h) on hydrogen sulfide, total reduced sulfur (TRS), ammonia, methane, and nitrous oxide stability in Tedlar and FlexFoil bags. Average gas concentrations ranged from 771 to 2,655 ppb, from 782 to 2,750 ppb, from 657 to 1,997 ppb, from 10,441 to 13,803 ppb, and from 337 to 344 ppb for H2S, TRS, NH3, CH4, and N2O, respectively. Bag reusability and background contamination were also investigated. Percent recoveries from FlexFoil bags ranged from 75% to 99.5% for all gases and concentrations except for TRS at high concentrations. For TRS at high concentrations, percent recovery from FlexFoil bags was 68.8%. No gas desorption or permeation was observed when using new FlexFoil bags. FlexFoil bags were more durable than Tedlar bags to mechanical stress and aging effects. There was no need to use a cover for FlexFoil bags to protect samples from sunlight. The cost of FlexFoil bags was lower than that of Tedlar bags.

Assessment of Environmental Tobacco Smoke Contamination in Public Premises: Significance of 2,5-Dimethylfuran as an Effective Marker

Contamination by environmental tobacco smoke (ETS) on premises where smoking is permitted is evaluated. Although all target VOCs evaluated show significant differences between smoking and nonsmoking indoors, the results obtained indicate that 2,5-dimethylfuran is the most appropriate and effective marker of ETS contamination given that this compound is only detected in environments where people have smoked and so the detection of this compound cannot be attributed to other contamination sources such as traffic. Moreover, the air levels of this compound due to coffee aroma are below the detection limits for this methodology. A preliminary study is performed to evaluate whether 2,5-dimethylfuran, a smoking breath biomarker, can be detected in passive smokers working in smoking environments. The compound was continuously detected in the breath of nonsmoking employees after being in direct contact with ETS for just a few hours. The Tedlar gas sampling bags had 5% loss of 2,5-dimethylfuran after 3 h of storage, which we took as the maximum recommended period for air sample storage.

Suitability of Tedlar ® gas sampling bags for siloxane quantification in landfill gas

Landfill or digester gas can contain man-made volatile methylsiloxanes (VMS), usually in the range of a few milligrams per normal cubic metre (Nm 3). Until now, no standard method for siloxane quantification exists and there is controversy with respect to which sampling procedure is most suitable. This paper presents an analytical and a sampling procedure for the quantification of common VMS in biogas via GC–MS and polyvinyl fluoride (Tedlar ®) bags. Two commercially available Tedlar bag models are studied. One is equipped with a polypropylene valve with integrated septum, the other with a dual port fitting made from stainless steel. Siloxane recovery in landfill gas samples is investigated as a function of storage time, temperature, surface-to-volume ratio and background gas. Recovery was found to depend on the type of fitting employed. The siloxanes sampled in the bag with the polypropylene valve show high and stable recovery, even after more than 30 days. Sufficiently low detection limits below 10 μg Nm −3 and good reproducibility can be achieved. The method is therefore well applicable to biogas, greatly facilitating sampling in comparison with other common techniques involving siloxane enrichment using sorption media.

Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge

Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 °C) and mesophilic temperature (35 °C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 °C) and 2.24% (at 35 °C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 °C. On the other hand, the PLA degradation started in 55 days at 35 °C and degradation rate was much slower than at 55 °C.

Pilot Scale Facility to Determine Gaseous Emissions from Livestock Slurry during Storage

Livestock production is a growing source of air pollution, locally and to the wider environment. Improved livestock manure management has the potential to reduce environmental impacts, but there is a need for methodologies to precisely quantify emissions. This paper describes and evaluates a novel storage facility for livestock slurry consisting of eight 6.5-m(3) cylindrical units. The stores may be equipped with airtight covers and ventilated during storage or during measurement only. Each store has eight air inlets (160 mm diameter) and a single outlet in the cover connected to a main ventilation duct. The stores can also be used as static enclosures. Ventilation can be regulated within the range of 50 to 250 m(3) h(-1). A gas sampling line enables sampling of odorants using automatic thermal desorption tubes, ammonia using acid traps, and greenhouse gases using gas sampling bags (pooled samples) or a syringe (time point samples). Complete recovery of CH(4) independent of ventilation rate was demonstrated. Vertical profiles of CO(2) and CH(4) above the slurry surface with and without ventilation and mixing of the headspace indicated methane oxidation activity in the surface crust. p-Cresol and 4-ethyl phenol emission from pig slurry was identified by GC-MS analysis of odor collected on adsorption tubes. Ammonia emissions between 0 and 166 mg N m(-2) h(-1) were observed during storage of pig slurry with and without surface crust and cover. A comparison of pooled and averaged time point measurements of CO(2), CH(4), and N(2)O indicated that pooled samples account for the diurnal variations under realistic storage conditions.

Anaerobic biodegradation tests of poly(lactic acid) and polycaprolactone using new evaluation system for methane fermentation in anaerobic sludge

The anaerobic biodegradation tests of polycaprolactone (PCL) and poly(lactic acid) (PLA) powders were done at thermophilic temperature (55 °C) under aquatic conditions (total solid concentrations of the used sludge were 1.73% (undiluted sludge) and 0.86% (diluted sludge)) using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. The biodegradation of PCL powder (10 g, 125–250 μm) in the diluted sludge stopped in about 47 days when the biodegradability reached 92%. The biodegradability of PLA powder (10 g, 125–250 μm) in undiluted sludge was 91% at about 75 days. The biodegradability of PLA powder (10 g, 125–250 μm) in diluted sludge was 79% at about 100 days. The biodegradability of PLA powder (5 g, 125–250 μm) in diluted sludge was 80% at about 85 days. It was found that the PCL and PLA powders were quite degraded using the new evaluation method. In addition, the smaller particle size PCL powder was biodegraded faster.

Formaldehyde and acetaldehyde adsorption properties of heat-treated rice husks

Rice husk (RH) was converted into an adsorbent to remove two types of aldehyde vapor. Japanese RH was carbonized at 250–800 °C in N 2 or activated at 875 °C in CO 2. The carbonized and activated RHs were exposed to formaldehyde vapor at 1.0 vol. ppm or acetaldehyde vapor at 100 vol. ppm (both in N 2 carrier gas) in enclosed 5-L gas-sampling bags. The RH activated at 875 °C showed the fastest decrease in formaldehyde and acetaldehyde concentrations in the bags. The rate of aldehyde adsorption was higher for activated RH than for commercial granular coconut-shell activated carbon (GCSAC), whereas the specific surface area and total pore volume for activated RH (466.9 m 2/g and 0.35 cm 3/g) were much lower than for GCSAC (1119.7 m 2/g and 0.57 cm 3/g). The surface basicity of activated RH and RH carbonized at high temperature, attributed to intrinsic inorganic K and Ca compounds, enhanced the surface uptake of aldehydes.

Development and comparisons of efficient gas-cultivation systems for anaerobic carbon monoxide-utilizing microorganisms

We describe a system for the cultivation of gaseous substrate utilizing microorganisms that overcomes some of the limitations of fixed volume culture vessels and the costs associated with sparging. Cali-5-Bond™ gas-sampling bag was used as the culture vessel. The bags contain approximately six times more mass of CO than the 40 mL vials at 1 atm of pressure and performed equally to the 40 mL vials in terms of their ability to maintain the composition of the gas over extended incubation times. Experiments using Clostridium ljungdahlii and CO as the sole carbon and energy source in both the gas sampling bag cultivation system and the traditional vial system demonstrated that this culture had a 15× increase in optical density in 24 h of incubation. The gas-sampling bags offer a viable alternative to gas sparging while overcoming the limitations of fixed volume culture vessels.

Analysis of human breath samples with a multi-bed sorption trap and comprehensive two-dimensional gas chromatography (GC×GC)

A multi-bed sorption trap designed to quantitatively collect volatile organic compounds from large-volume vapor samples and inject them into a gas chromatograph is combined with a comprehensive two-dimensional gas chromatograph (GCxGC) for the analysis of organic compounds in human breath samples. The first-column effluent of the GCxGC is modulated by a single-stage, resistively-heated and air-cooled segment of 0.18-mm i.d. stainless steel column using the same stationary phase as the first column. Cooling gas is provided by a two-stage conventional refrigeration system, and thus no consumables other than carrier gas and electric power are required. The sorption trap uses four discreet beds, three containing different grades of graphitized carbon and one containing a carbon molecular sieve. The ordering of the beds in the trap tube is from the weakest to strongest adsorbent during sample collection. Breath samples are collected in gas sampling bags, and samples are passed through the trap at a flow rate of about 50 cm3/min. After sample collection, hydrogen carrier gas flow is initiated in the direction opposite to the sample collection flow, and the metal trap tube is resistively heated to inject a sample plug into the GCxGC. Performance data for the combined GCxGC/sorption-trap instrument is described, and human breath-sample chromatograms are presented.

Determination of gas phase adsorption isotherms—a simple constant volume method

Single and ternary solute gas phase adsorption isotherms were conducted in this study to evaluate the effectiveness of a simple constant volume method, which was utilized by using Tedlar gas sampling bags as a constant volume batch reactor. For this purpose, gas phase adsorption of toluene, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) on two types of activated carbons, BPL—bituminous base and OVC—coconut base, were investigated. For the single solute adsorption, the experimental adsorption data were found to be well correlated with Freundlich and Myers adsorption equations. The pore size distribution of adsorbents was found to affect their adsorption capacities; its effect was dependant on the solute concentration. The ternary adsorption experimental isotherms were accurately predicted by using the well-known model, i.e., ideal adsorbed solution theory (IAST).

Comparison of single-breath and tidal breathing exhaled nitric oxide levels in infants

The aim of this study was to compare two different methods, tidal breathing (TB) and single-breath (SB), for measuring fractional exhaled nitric oxide (FENO) in infants. FENO was measured in 71 infants with either recurrent wheeze (n=32), recurrent cough (n=16) or no symptoms (healthy, n=23) using both methods. For TB measurements five breaths were collected into a gas sampling bag (off-line reservoir sampling). The SB method was modified from the raised volume rapid thoraco-abdominal technique. Agreement between the two methods was investigated and both methods were used to compare FENO in infants with and without symptoms. Flow dependence of SB FENO was demonstrated using two expiratory flows (11 and 40 mL x s(-1)). There was a moderate correlation (r=0.60) but poor agreement between levels using the TB and SB methods. A significant difference in FENO between healthy children and children with wheeze was found using the SB but not the TB method. Due to lower expiratory flow and reduced nasal nitric oxide contamination the single-breath technique may be more sensitive than the tidal breathing method for detecting differences in exhaled nitric oxide between infants with and without respiratory symptoms.

Analysis of Sidestream Smoke VOCs and Characterization of their Odor Profiles by VOC Preconcentrator-GC-O Techniques

Abstract Various techniques have been employed in the analysis of volatile organic compounds (VOCs). However, these techniques are insufficient for the precise analysis of tobacco smoke VOCs because of the complexity of the operating system, system instability, or poor sensitivity. To overcome these problems, a combined system of VOC preconcentrator, gas chromatograph, and olfactometer has been developed. The performance of this new system was evaluated in the analysis of VOCs in tobacco smoke and applied to the odor profiling of sidestream smoke (SSS) that has not been sufficiently investigated in the past. A VOC sample in a gas-sampling bag was injected into a gas chromatograph through a preconcentrator, where it was concentrated, dehydrated, and cryo-focused. Separated VOCs were introduced into a mass spectrometer (for qualitative and quantitative analysis) and a sniffing port (for odor profiling) by a splitting device. In addition to the conventional Gas Chromatography-Olfactometry (GC-O) technique that was used for describing the odor quality of each compound, the odor intensity was estimated based on the dilution ratio of the sample, Aroma Direct Dilution Analysis (ADDA). Also, the contribution of each VOC to the overall SSS odor was estimated by sensory evaluation. This system permitted adequate characterization of the VOCs. The reproducibility of quantification was also good enough with Coefficient of Variation (CV) values less than about 5% (n = 5). With the GC-O technique, we obtained an SSS odor profile composed of over 30 odorants. ADDA indicated that seven odorants were sufficient to characterize SSS odor. In addition, the omit-test revealed that three odor attributes, (‘metallic’, ‘potato-like’, and ‘popcorn-like’) were most important for the characterization of SSS odor.

Collection of atmospheric carbon dioxide by a gas sampling bag for its oxygen isotopic analysis

Collection of atmospheric carbon dioxide by a gas sampling bag for its oxygen isotopic analysis

Odor Concentration Decay and Stability in Gas Sampling Bags

This paper presents results of an experimental study into factors contributing to decay of odor samples during storage, between 4 and 40 hr after sample collection. The odor studied was sampled from a tobacco processing plant as part of collaborative research with a view to establishing a manual outlining methods for odor annoyance management, specifically for the tobacco industry. In August and September 1997, an experimental program was carried out in which two types of tobacco odor were sampled: Burley Toaster and Mix. The dependent variable was odor concentration in the bag, measured by dynamic olfactometry in accordance with the draft Comité Européen de Normalisation (CEN) standard EN13725 “Air Quality— Determination of Odor Concentration by Dynamic Olfactometry.” The independent variables were sampling bag material, degree of dilution during sampling, dilution gas used, particle removal during sampling, and age of sample in hours. In the first phase, 94 odor analyses were carried out. In a second test, 32 samples were analyzed for odor concentration. In addition, 16 samples were analyzed using gas chromatography-mass spectrometry (GC-MS). Analysis of the results (analysis of variance) led to the unexpected conclusion that Nalophan film bags performed significantly better than metalized Cali-Bond layered film as a bag material. The odor concentration of samples in Nalophan bags remained relatively stable between 4 and 12 hr after sampling. After 30 hr, decay to about half the initial concentration, as measured at 4 hr, was observed. Particle removal during sampling caused the odor concentration in the bags to be reduced by approximately 20%. For practical reasons, particle removal remains useful, to avoid contamination of equipment. Using air or nitrogen as the neutral gas for pre-dilution during sampling or the dilution factor used (between factor 2 and 6) did not appear to have an effect on the decay characteristic of odor samples. The following recommendations are suggested for the practice of collecting odor samples and apply specifically to tobacco processing emissions: • Analyze samples as soon as possible, preferably within 12 hr; • When samples age for more than 12 hr, decay is likely to cause a reduction in odor concentration to half the original concentration at age 30 hr; • Use sampling bags made of Nalophan NA or benchmark performance of other materials against Nalophan NA before using alternative materials; • Use pre-dilution when sampling only for the purpose of avoiding condensation during sample storage. Use an appropriate minimum dilution factor to avoid condensation; • Both nitrogen and high-purity (synthetic) air are suitable to use as neutral gas for pre-dilution; and • When sampling tobacco odors, use an odorless filter to remove particles. This practice removes a source of variation and avoids contamination of equipment. The effect on results, despite being consistently lower in odor concentration, is not meaningful in terms of perceived intensity or annoyance potential.

A programmable gas sampler to measure the average radon concentration in a test chamber or in the field.

A Tedlar gas sampling bag was used to retain samples of the test environment of interest. Samples, typically hourly, were transferred into a gas sampling bag. The volume of each sample was determined by a programmable timer or any computer capable of executing a compiled basic program. The program automatically adjusted the sample volume of each increment to exactly compensate for radioactive decay of radon referred to the end of the exposure period. At that time the radon activity collected in the sampling bag was the exact average for the whole period. A single Lucas cell was used to report the average concentration for typically 2 and 3 day exposures. The results compared with calculated predictions and with the average of a series of grab samples taken during the measurement period. The benefit of this method was the large work load reduction needed to determine the average concentration from a series of grab samples and the ability to employ Lucas cells, which are inherently more stable and less expensive than active measurement equipment normally used for chamber standardizations.

Closed-system trapping method for the direct determination of transport efficiency in electrothermal vaporization sample introduction

A novel closed-system for the direct determination of analyte transport efficiency in electrothermal vaporization (ETV) sample introduction is described. A commercially available gas-sampling bag filled with 100 ml of 10% HNO 3 was connected to the exhaust of an ETV system and used to collect and seal the product of an electrothermal vaporization event. The bag was then manually agitated, and its liquid contents decanted and analyzed by solution nebulization ICP-MS. Analyte transport efficiency values were found to be in statistical agreement with those determined by a reference method on the same ETV system for a variety of volatile (As, Cd, Mn, Pb), involatile (Cu, Ni) and refractory carbide forming (V) elements. This simple experimental setup captures all of the analyte in a single solution, with the closed-system element of its design ensuring that this is done quantitatively. Absolute detection limits for most elements were of the order of 0.1–10 ng absolute for the technique, making it well suited for analyte masses typically vaporized in ETV-ICP-OES. The relative merits of using this type of setup for the determination of analyte transport efficiency in ETV sample introduction, along with experimental considerations, are described.

Breath ethane as a marker of reactive oxygen species during manipulation of diet and oxygen tension in rats.

Breath ethane, O2 consumption, and CO2 production were analyzed in 24-mo-old female Fischer 344 rats that had been fed continuously ad libitum (AL) or restricted 30% of AL level (DR) diets since 6 wk of age. Rats were placed in a glass chamber that was first flushed with air, then with a gas mixture containing 12% O2. After equilibration, a sample of the outflow was collected in gas sampling bags for subsequent analyses of ethane and CO2. The O2 and CO2 levels were also directly monitored in the outflow of the chamber. O2 consumption and CO2 production increased for DR rats. Hypoxia decreased O2 consumption and CO2 production for the AL-fed and DR rats. These changes reflect changes in metabolic rate due to diet and PO2. A significant decrease in ethane generation was found in DR rats compared with AL-fed rats. Under normoxic conditions, breath ethane decreased from 2.20 to 1.61 pmol ethane/ml CO2. During hypoxia the levels of ethane generation increased, resulting in a DR-associated decrease in ethane from 2.60 to 1.90 pmol ethane/ml CO2. These results support the hypothesis that DR reduces the level of oxidative stress.

Measurement of the composition of gas desorbed from coal by gas chromatography

Direct methods for the determination of the gas content of a coal seam are based upon extracting a coal sample, enclosing it in a sealed container and measuring the volume of the gas evolved. In our work we measured evolved gas as a function of time, type and quantity of low rank coal (lignite) at normal (atmospheric pressure and temperature) conditions. The evolved gas was, collected in gas sampling bags and analyzed by GC for its main components (carbon dioxide, methane and dimethyl sulfide). From the parameters obtained (gas volume, CH4:CO2 ratio, rate of gas desorption, time concentration profile and different lithotypes of lignite) a more detailed identification of hazardous areas in underground coal extraction could be ensured.

97/03960 Modernization of central-heating boilers

Nitrous oxide (N2O) was measured in the flue gas at a number of large (500 and 660 MW) coal-and oil-fired power station boilers. Measurements were made on-line by non-dispersive infrared spectrometry, and off-line by gas chromatography on samples collected in gas sampling bags. N2O concentrations in flue gas from all boiler types were low; generally in the range <1 to <5 ppm. The N2O concentrations measured were affected by the sampling conditions at the individual stations. The most satisfactory sampling conditions gave the lowest N2O values, and the true values for N2O concentrations in flue gas are likely to lie at the low end of the measured range, at 1–2 ppm or less. Within the resolution of the measurements, no dependence of N2O emissions on boiler (wall-fired or corner-fired) or burner type (standard or low NOx) was detected. Both coal- and oil-fired boilers gave similarly low emissions of N2O. The greenhouse impact of N2O from conventional fossil-fuelled plants is <1% of the contributed by the corresponding CO2 emissions.