Gas-tight Syringe Research Articles

Molecular sieves: an alternative method of carbon dioxide removal which does not generate compound A during simulated low-flow sevoflurane anaesthesia.

Molecular sieves are used in industry to 'scrub' industrial gases. We examined, during simulated low-flow closed system anaesthesia, (1) the carbon dioxide adsorbing potential of molecular sieves and (2) the reactivity of the sieves compared to soda lime using sevoflurane as an indicator. A low-flow anaesthetic system containing 13X molecular sieves was connected to a model lung. End-tidal concentrations of CO2 were measured continuously at an O2 flow of 800 ml.min-1 and a CO2 flow of 200 ml.min-1. In the second study, sevoflurane (FE'sevo 1.7%) was added to the system after which samples were taken from the inspiratory limb of the anaesthetic system. This experiment was performed both during carbon dioxide removal with soda lime and with the molecular sieves. The samples were stored in gas-tight syringes and analysed by gas chromatography. The temperature of both absorbents was measured throughout the study. The molecular sieves adsorbed carbon dioxide (20%) efficiently for a period of 5 h. There was a gradual increase from the baseline of 4.4% to 4.5, 5.4, and 6.0% at 90, 180, and 300 min, respectively. When sevoflurane was added to the system, compound A was detected at the start of both experiments. However, when soda lime was used the concentrations of compound A increased 10-fold after 2.5 h compared with baseline values. No increase in compound A was observed when molecular sieves were used for carbon dioxide removal. The highest mean (SD) temperature of the molecular sieves was 41.5 (3.2) degrees C. Molecular sieves are effective adsorbents of carbon dioxide when used in a simulated low-flow, closed anaesthetic system.(ABSTRACT TRUNCATED AT 250 WORDS)

Mass Spectrometry Analysis of the By-products of Intrastromal Photorefractive Keratectomy

To determine the nature and chemical composition of the cavitation bubbles generated by intrastromal photorefractive keratectomy (IPRK) with the Neodymium: Yttrium Lithium Fluoride (Nd:YLF) picosecond laser. IPRK was performed on the corneas of three fresh human cadaver eyes with the Nd:YLF picosecond laser. High energy levels of 200 mJ/pulse to 300 mJ/pulse were used to produce the maximum amount of gas within the corneal stroma. The cavitation bubbles produced in the stroma were aspirated using a gas-tight syringe connected to a valve, and the specimens were analyzed with a mass spectrometer. The experiment was performed on three different occasions using one cadaver eye in each experiment. The analysis consistently revealed a mixture of carbon dioxide, carbon monoxide, water vapor, oxygen, and nitrogen. Atmospheric control samples also revealed oxygen and nitrogen. No other components were detected. The gaseous by-products of IPRK with the picosecond laser result from the simple breakdown of stromal tissue and contain no toxic or unexpected components. We found that these gaseous products are capable of rapid elimination by absorption or diffusion out of the intact cornea.

Determination of growth of anaerobic fungi on soluble and cellulosic substrates using a pressure transducer

Summary: A pressure transducer was used to determine the accumulation of fermentation gases during growth of Neocallimastix hurleyensis and Caecomyces communis on soluble (glucose) and particulate (cellulose and wheat straw) carbon sources. The anaerobic fungi were grown in submerged batch culture in gas-tight bottles using conventional anaerobic techniques. As the fermentation progressed, fermentation gases accumulated in the head-space of culture bottles causing an increase in the head-space gas pressure. Gas was measured and released using a pressure transducer connected to a digital readout voltmeter and gas-tight syringe assembly. By repeating this gas measurement-release procedure at regular intervals during the fermentation, and summation of the calculated (regression corresprected) gas volumes, gas accumulation profiles were constructed. For cultures grown on glucose, this technique enabled the growth of anaerobic fungi to be evaluated without destructive sampling of the fungal culture. The resultant gas accumulation profiles were related to glucose loss and biomass accumulation and could be used to determine specific growth rates, doubling times and fermentation gas yields. For cultures grown on cellulose and wheat straw, measurement of gas accumulation enabled growth phases and the course of the fermentation to be easily monitored. The results obtained establish the pressure transducer as an instrument for rapid, precise and reproducible determination of the growth of anaerobic fungi on soluble and particulate substrates.

Modified Indigo Method For Gaseous And Aqueous Ozone Analyses

Abstract The indigo method developed by Bader and Hoigne for aqueous ozone analysis was modified to allow for both gaseous and aqueous ozone determination. Gas or water samples were extracted with a gas-tight syringe containing a known volume of indigo reagent. The modified procedure provided a more consistent basis for gaseous and aqueous ozone determination allowing for more accurate ozone mass balance calculations. Direct gaseous ozone UV absorbance with molar absorptivity of 3,000 M−1cm−1 at 258 nm was used as primary standard to determine the molar absorptivity of the indigo reagent. The molar absorptivity of indigo reagent, assuming a 1:1 stoichiometric ratio for the reaction between indigo and ozone, was determined to be 23,150 ± 80 M−1cm−1, or approximately 16 percent higher than that of 20,000 M−1cm−1 suggested by Bader and Hoigne. An independently calibrated membrane-electrode ozone monitor showed good correlation with indigo method results using the molar absorptivity value determined in this s...

A simple gas production method using a pressure transducer to determine the fermentation kinetics of ruminant feeds

This paper describes a simple yet sensitive laboratory procedure that was developed to provide detailed information on the fermentation kinetics of ruminant feeds. In principle, the technique is similar to other in vitro digestibility procedures using ground particulate substrates, anaerobic media and a rumen fluid inoculum. It differs, however, in that incubations are conducted in gas-tight culture bottles, thus enabling gases to accumulate in the head-space as the fermentation proceeds. A pressure transducer connected to a digital readout voltmeter and gas-tight syringe assembly is then used to measure and release the accumulated gas pressures from the incubating culture bottles. By repeating this gas-measurement, gas-release procedure at regular intervals during the fermentation, it is possible to construct gas accumulation profiles for feeds by summation of regression-corrected gas volumes. These profiles are then described using a recently derived growth function developed to characterise gas production profiles. Results obtained establish the pressure transducer as a suitable tool for determining the fermentation kinetics of ruminant feeds and ranking them with respect to their in vitro fermentability.

Mixing of a Point Source Pollutant by Natural Convection Flow within a Room

Indoor air quality models are commonly based on the assumption of instantaneous and complete air mixing within a zone. Such an assumption is not appropriate for all circumstances, such as investigating the utility of segregating smokers to reduce nonsmoker exposure to environmental tobacco smoke. This experimental study characterizes quantitatively the rate at which smoke from a cigarette disperses within an unoccupied, 31-m3, low air-exchange rate room under natural convection flow conditions. Sidestream smoke from a smoldering cigarette was simulated with a pulsed release of a tracer gas – a neutrally buoyant mixture of sulfur hexafluoride (SF6) in helium – above an electrically heated coil. During each experimental run, sequential air samples were collected remotely, using gas-tight syringes, from 41 locations within the room. After each run, these samples were analyzed for SF6 content using a gas chromatograph with an electron-capture detector. Duplicate runs were conducted under three conditions: nearly isothermal surfaces; convection from a 500–watt heater; and convection from incoming solar radiation. Characteristic mixing times ranged from 7–10 minutes for the solar radiation case to 80–100 minutes for the nearly isothermal case.

Partial Characterization of Volatile Fungistatic Compound(s) from Soil

Many soils contain volatile, water-soluble compound(s) that inhibit germination of Cochliobolus victoriae conidia in the absence of a carbon source. The volatile fungistatic compound(s) from soil were separated into a cell-free extract. Loss of fungistatic activity from the extract was time- and temperature-dependent; all activity was lost within 5 min at 90 C, 48 h at 21 C, and 5 days at -70 C. Much of the fungistatic activity was lost after the soil extract was diluted by 10%, incubated in an uncapped vial, or transferred to a new vial via a gas-tight syringe. Fungistatic activity was not detected in material collected from soil into a liquid N 2 cold trap [...]

Methyl Bromide Determination in Selected Foods by Headspace Technique

A headspace method used earlier for determining methyl bromide (MB) in assorted nuts and peanut butters has been successfully applied to other foods that could potentially contain traces of this toxic fumigant. The foods tested include 63 off-the-shelf spices and seasonings, 83 table-ready items (grain-based, dried, or highly seasoned), 30 dried fruits and trail mixes, and 38 oil-based items (oil-seeds, cooking oils, or spicy oil-based dressings). Sample headspace gas is produced by blending < or = 50 g sample in 250 +/- 50 mL aqueous solution in a sealed 1000 mL blender cup. After equilibration at 25 degrees C, the headspace is sampled with a gas-tight syringe and injected into a dual column-dual detector gas chromatograph. One determination is made with a 20% OV-101 packed column and a 63Ni electron capture detector (ECD), the other with a GS-Q wide-bore capillary column and a Hall electrolytic conductivity detector (HECD). Of the approximately 200 samples tested, none contained detectable MB residue at a quantitation limit < 100 ng/g sample. All fortified samples yielded MB recovery. Samples were fortified at levels ranging from 78 to 3250 ng MB/g. Recoveries ranged from a mean high of 56% for spices and seasonings to a mean low of 30% for oil-based foods. The overall recovery and CV, including the results from assorted nuts and peanut butters, were 46 and 33%, respectively.

Estimation of perimortal percent carboxy-heme in nonstandard postmortem specimens using analysis of carbon monoxide by GC/MS and iron by flame atomic absorption spectrophotometry.

In decomposed, formalin-fixed, embalmed, exhumed, and some fire-dried cases in which normal blood is unavailable, the usual methods for determination of carboxyhemoglobin saturation frequently fail. To address these specimens, a method utilizing both gas chromatography/mass spectrometric (GC/MS) determination of carbon monoxide (CO) and flame atomic absorption spectrophotometry (FAAS) determination of iron (Fe), in the same specimen, was developed. The method is reported here, along with its application to seven pertinent forsensic death investigations. The CO analytical methodology involves acid liberation of the gas from the specimen aliquot in a headspace vial. After heating and equilibrating, a sample of the headspace vapor is injected into the GC/MS system with a gastight syringe. Quantitation is achieved by standard addition comparison utilizing the ideal gas law equation. Iron is quantified by FAAS analysis of the same aliquot used for the CO determination, following nitric acid digestion. The concentration is determined by comparison to a standard curve. A formula for determining the minimum percent carboxy-heme saturation was derived by using the ratio of the amount of CO to the amount of Fe in the aliquot analyzed. Tissue types analyzed include spleen, liver, muscle, dried blood, and unspecified decomposed tissue.

Headspace Method for Rapid Determination of Methyl Bromide in Assorted Nut Samples

Abstract A headspace method has been developed for the rapid, safe determination of methyl bromide (MeBr) in raw and processed nuts. Fifty grams of frozen nut meats is blended 3 min at high speed in 200-250 mL aqueous solution in a sealed 1 L blender cup fitted with a septum port on its cover. The cup is equilibrated 10 min in a 25C water bath. Two 250 ±150 μL aliquots of the sample headspace gas are sequentially removed with a gas-tight syringe and injected into a dual column/ dual detector gas chromatograph. One determination is made with a GS-Q wide-bore capillary column and a Hall electrolytic conductivity detector, the other with a packed column, 20% OV-101 on Chromosorb W(HP), and a 63Ni electron capture detector. The average variation for the manual injections is about 5% for both column/detector systems. To prevent random emission of MeBr during the determination, dated standards, headspace wastes, and electron capture detection effluent are passed through liquid traps. The overall recovery of MeBr from fortified samples is about 40%; the coefficient of variation is 29%. Eighteen assorted nut samples were analyzed on both systems at a quantitation limit of ᑉ100 ng/g; no detectable MeBr was found.

Gas Chromatographic Method for Determination of Dimethylamine, Trimethylamine, and Trimethylamine Oxide in Fish-Meat Frankfurters

A method is described for analysis of minced fish-meat and surimi-meat frankfurters for dimethylamine (DMA), trimethylamine (TMA), and trimethylamine oxide (TMAO) using a headspace-gas chromatographic technique. After simple acid extraction and addition of NaOH, the headspace was directly injected into a gas chromatograph by a gas-tight syringe. DMA and TMA were separated on a Chromosorb 103 column and detected by a flame ionization detector. TMAO was measured as TMA after Zn reduction. Repeatability of the method for DMA, TMA, and TMAO was 6.6, 1.0, and 18.8 ppm, respectively. The method was applicable to Alaska pollock-meat and Atlantic menhaden-meat frankfurters, unwashed, and washed mince and surimi.

Gas Chromatographic Analysis of Toxic Edemagenic Inhalation Compounds

Abstract Different megabore column and packed column phases were evaluated for their suitability in the gas chromatographic analysis of three toxic polyhalogenated compounds (phosgene, TFD, and PFIB). Adsorbent type stationary phases provide better retention and separation for the volatile fluorocarbons than do polar and nonpolar liquid phases. The reactivity of phosgene precludes the use of many phases having hydroxy, amino, or cyano functional groups. Silica gel is still the column of choice for phosgene. The use of gas sampling bags and gas-tight syringes can provide reliable quantitation of these compounds in air samples. TFD and PFIB eexhibit different electron capture mechanisms and detector temperature dependency. The mechanisms are supported by the results of negative ion mass spectrometry.

COLLECTION OF PLANT VOLATILES USING HEADSPACE METHODS

Two methods for collecting headspace vapors produced by plant samples are presented. The first involves entraining volatiles in a stream of air and trapping the entrained compounds on a porous polymer such as Tenax. The volatiles are recovered from the trap by solvent extraction or heat desorption and analysed by gas chromatography. A second method entails removing headspace vapor above plant material with a gas-tight syringe and injecting the sample directly into the gas chromatograph. An evaluation of the usefulness of these techniques will be presented.

A Method for the Rapid Analysis of Headspace Volatiles of Raw and Roasted Peanuts

ABSTRACTA rapid headspace analysis method for evaluating the flavor quality of peanuts using gas chromatography has been developed and tested. Samples are ground, heated in glass vials for 30 min at 150°C, and the headspace injected using a gas tight syringe. After initial startup, one can screen samples for flavor defects at the rate of four per hour. Of the peaks produced from peanut headspace analysis, most have been identified by gas chromatography/mass spectrometry and eight have been related to specific flavor characteristics.

A simple and versatile end-sealing for static coating of wide-bore glass capillaries

An end-sealing method to be used for static coating of wide-bore glass capillaries is described. After the capillary was completely filled with the coating solution, one end is connected to a gas-tight syringe (10-ml volume) via silicone tubing and the other end is fixed with shortcutted silicone tubing for sealing with a plug. The method is highly successful.

Headspace gas chromatography of stimulants in urine by in-column trifluoroacetyl derivatization method

The analysis of stimulants in urine using a headspace gas chromatography system equipped with an in-column sample trifluoroacetylation unit was investigated. A 5-ml aliquot of urine containing stimulants was pipetted into a 20-ml autosampler vial together with 3.5 g of potassium carbonate. The vial was sealed and heated for 20 min at 80°C, then 0.8 ml of the headspace gas and N-methylbis(trifluoroacetamide) gas were injected simultaneously into the gas chromatograph equipped with a flame ionization detector and a fused-silica capillary column (DB-1, 30 m × 0.32 mm I.D., film thickness 0.25 μm), with a gas-tight syringe. Calibration graphs prepared by the absolute calibration curve method showed good linearity over the concentration range of 0.04 to 50 μg/ml for methamphetamine hydrochloride and amphetamine sulphate. The detection limits were 0.03 μg/ml for both of these compounds.

Determination of volatile aromatic hydrocarbons in estuarine and coastal sediments using gas syringe injection of headspace vapours and gas chromatography with flame-ionisation detection

A simple, low cost flame-ionisation detection method for the determination of volatile aromatic compounds in estuarine and coastal sediments is described. Headspace vapours are drawn from a modified sample vessel at 80 °C and injected by means of a gas-tight syringe with a valved needle. The method eliminates the difficulties normally encountered with solvent extraction and dynamic “non-equilibrium” headspace methods. The effect of varying the sample preparation parameters is discussed and results giving the optimised values are presented. Relative standard deviations of less than 2% were achieved for a variety of sub-marine and tidal sediments and the results were found to be superior to those given by an existing solvent extraction method. The limits of detection of the method are below 0.5 µg kg–1(dry mass) for ten key volatile organic aromatic compounds and the response is linear up to at least 200 µg kg–1.

Analysis of stimulants in urine by head space gas chromatography.

We analyzed stimulants in the urine by automated head-space gas chromatography. A 6-ml of urine-containing stimulants was pipetted into a 20 ml autosampler vial together with 0.5 ml of 20% sodium hydroxide and 3.5 g of potassium carbonate. After the vial was sealed and heated for 20 min at 80°C, 0.8 ml of the head space gas was injected into the gas chromatograph equipped with a FID and fusedsilica capillary column (DB-17 : 30 m×0.32 mm i.d., film thickness 0.5 μm), by using Hamilton gas tight syringe. Addition of potassium carbonate to the urine increased the detection limit 10 to 100 times. The calibration curves showed a linearity in the range of 0.1 to 15 μg/ml for methamphetamine and amphetamine. The relative standard deviations were 4.8% for methamphetamine and 4.1% for amphetamine when the stimulants concentration was 10 μg/ml. Detection limits of methamphetamine and amphetamine were 0.02 μg/ml and 0.05 μg/ml, respectively.

A simple determination method of bromide ion in plasma of methyl bromide workers by head space gas chromatography

An improved method for the simple determination of bromide ion in plasma is described. It was modified from the method by Kawai, Sugiyama et al. (1985). In the improved method, 200 microliters of plasma and 800 microliters of distilled water were placed in a reaction vial to which 100 microliters of dimethyl sulfate was added. The reaction vial was immediately sealed, placed in an incubator at 85 degrees C, and shaken for 10 min. At the end of the reaction, a gas-tight syringe was used to draw out the head space gas of 1 ml. The methyl bromide gas was then injected into a gas chromatograph and methyl bromide was determined with F.I.D. A good linear relationship was obtained between the peak area of methyl bromide and the concentration of bromide ion within the range of 0.5 to 500 ppm. Bromide ion in the range of 0.5 to 500 ppm in standard solution was added to the plasma samples. After 10 repeated measurements, the relative standard deviation was found to be in the range of 2.8-3.6% and recovery was over 96%. The analytical results of this method were compared with those obtained by spectrophotometry. The analytical results obtained by the two methods were in good agreement (r = 0.9669) in plasma samples of 10 methyl bromide workers. A study to determine bromide ion concentration in 39 methyl bromide workers was made and the results were compared with those observed in 100 workers (control group) not exposed to methyl bromide.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of trihalomethanes in water using gas syringe injection of headspace vapours and electron-capture gas chromatography

A simple, rapid electron-capture gas chromatographic method for the determination of trihalomethanes in water is described. Headspace vapours are withdrawn from the sample container at ambient temperature and injected by means of a gas-tight syringe with a valved needle, thus eliminating contamination problems associated with established liquid-liquid extraction and purge-and-trap methods. Simple precautions are adequate to minimise the effect of temperature fluctuations. Relative standard deviations of less than 2% were observed for treated river water samples, and the results were comparable to those of an established liquid-liquid extraction method.The limits of detection are below 1 µg l–1 and the response is linear up to at least 100 µg l–1.