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PubMed2001

Effect of pedological characteristics on aqueous soil extraction recovery and tert-butyldimethylsilylation yield for gas chromatography-mass spectrometry of nerve gas hydrolysis products from soils.

Detection and identification of alkyl methylphosphonate (RMPA) and methylphosphonate (MPA) are performed to verify the existence of nerve gases by gas chromatography-mass spectrometry (GC-MS) after tert-butyldimethylsilylation (TBDMS). However, it is sometimes difficult to detect RMPA and MPA in soils. This study examines the relationship between the pedological characteristics and the aqueous extraction recoveries and TBDMS derivatization yields of ethyl-, isopropyl- and pinacolyl methylphosphonate and MPA for 21 soil samples. The aqueous extraction recoveries were measured directly by capillary electrophoresis. Andosols showed low extraction recoveries, while Regosols and Fluvisols showed high recoveries. RMPA were extracted with higher recoveries than MPA from all soils. MPA could not be extracted from Andosols. Within the pedological characteristics, phosphate absorption coefficients showed a strong negative correlation with the extraction recoveries of all phosphonates. The levels of RMPA and MPA in aqueous soil extracts were also determined for eight soils by GC-MS after TBDMS. Compared to the aqueous extraction recoveries, the yields of TBDMS derivatives were low. Strong anion exchange led to a significant improvement in derivatization yields. The efficiencies of TBDMS derivatization were inversely correlated with the levels of alkaline earth metals extractable from soils when the three soils that possessed high total carbon were excluded.

Chemical Warfare Agents↗
PubMed1995

Determination of 8-oxoguanine in DNA by gas chromatography--mass spectrometry and HPLC--electrochemical detection: overestimation of the background level of the oxidized base by the gas chromatography--mass spectrometry assay.

Two analytical methods, one involving the combined use of reverse-phase HPLC and electrochemical detection (HPLC-EC) and one involving a mass spectrometric detection after gas chromatography separation (GC/MS), were developed for the detection of 8-oxoguanine in DNA. In order to obtain quantitative results, 2,6-diamino-8-oxopurine, whose chemical structure and electrochemical response are very similar to 8-oxoguanine, has been employed as an internal standard in the HPLC-EC assay. In the case of the GC/MS method, an isotopically stable (M + 4) 8-oxoguanine has been employed as an internal standard. Both methods are able to detect approximately 1 modification per 10(6) DNA bases. The background level of 8-oxoguanine in DNA as determined by GC/MS is approximately 50-fold higher than that determined by the HPLC-EC assay. The discrepancy between the two methods is due to an artifactual oxidation of guanine during the derivatization reaction as demonstrated by using pure guanine. The amount of 8-oxoguanine in guanine, determined by GC/MS, increases linearly with the time of derivatization, indicating that an oxidation occurs during the silylation reaction. Derivatization under nitrogen atmosphere reduces but does not suppress the artifactual oxidation. The amount of 8-oxoguanine in DNA, quantified by GC/MS, is comparable to that obtained by HPLC-EC when 8-oxoguanine is prepurified by HPLC or by immunoaffinity chromatography, prior to the silylation reaction. The artifactual formation of 8-oxoguanine during the derivatization reaction may explain, at least in part, why the values reported for 8-oxoguanine determination by GC/MS are generally about 1 order of magnitude higher than that determined by HPLC-EC. Prepurification of 8-oxoguanine from guanine is recommended in order to obtain reliable results by GC/MS which may be compared to HPLC-EC.

Animals↗
PubMed1987

Gas and liquid chromatography of hydroxybiphenyls, chlorinated hydroxybiphenyls and several types of halogenated derivatives. I. Capillary gas chromatography and mass spectrometry.

For 8 hydroxybiphenyls and 19 chlorinated hydroxybiphenyls derivatization reactions with 6 electrophilic reagents--viz., 4 perfluoro anhydrides, pentafluorobenzoyl chloride and tert.-butylpentafluorophenylmethylchlorosilane--have been studied to evaluate their potential for capillary gas chromatography with electron-capture detection. For some of the classes of derivatives, mass spectrometric data are presented.

Biphenyl Compounds↗
PubMed2001

Direct thermal desorption in the analysis of cheese volatiles by gas chromatography and gas chromatography-mass spectrometry: comparison with simultaneous distillation-extraction and dynamic headspace.

Direct thermal desorption (DTD) has been used as a technique for extracting volatile components of cheese as a preliminary step to their gas chromatographic (GC) analysis. In this study, it is applied to different cheese varieties: Camembert, blue, Chaumes, and La Serena. Volatiles are also extracted using other techniques such as simultaneous distillation-extraction and dynamic headspace. Separation and identification of the cheese components are carried out by GC-mass spectrometry. Approximately 100 compounds are detected in the examined cheeses. The described results show that DTD is fast, simple, and easy to automate; requires only a small amount of sample (approximately 50 mg); and affords quantitative information about the main groups of compounds present in cheeses.

Cheese↗
PubMed2006

The extraction and analysis of 1,4-dioxane from water using solid-phase microextraction coupled with gas chromatography and gas chromatography-mass spectrometry.

In this study, two methods are developed for the extraction of 1,4-dioxane (dioxane) from water using 80-microm carboxen-polydimethylsiloxane solid-phase microextraction fibers followed by either gas chromatography (GC)-flame ionization detection (FID) or GC-mass spectrometry (MS). With GC-FID, the lower limit of detection (LOD) for 1,4-dioxane is 2.5 microg/L (ppb) with a linear range of 5 to 10,000 microg/L, obtained by immersing the fiber in the sample for 20 min with agitation. Using GC-MS, the lower limit of quantitation is 0.5 microg/L, and the LOD is 0.25 microg/L. The upper linear range limit is 100 microg/L. Samples are extracted in 20 min using either heated headspace with agitation or direct immersion with agitation.

Dioxanes↗
PubMed1959

Analysis of gas in biological fluids by gas chromatography.

Combining a vacuum extraction method with gas chromatography makes possible accurate, reproducible determination of small quantities of permanent gases contained in biological fluids. One useful application is demonstrated by determining the oxygen tension in 1 ml of human plasma.

Biological Products↗
PubMed1993

Respiratory gas exchange using a triaxial alveolar gas diagram.

A triaxial alveolar gas diagram to depict fractional concentration of oxygen, carbon dioxide and nitrogen is described, in which the R = 1 line is always implicit. Although it is not claimed that this representation leads to new insights into respiratory physiology, a method of plotting on a triaxial coordinate system has been found to be well suited to many applications when a direct display of fractional nitrogen concentration is required.

Carbon Dioxide↗
PubMed2001

Ventilation-perfusion inhomogeneity increases gas uptake in anesthesia: computer modeling of gas exchange.

Ventilation-perfusion (VA/Q) inhomogeneity was modeled to measure its effect on overall gas exchange during maintenance-phase N(2)O anesthesia with an inspired O(2) concentration of 30%. A multialveolar compartment computer model was used based on physiological log normal distributions of VA/Q inhomogeneity. Increasing the log standard deviation of the distribution of perfusion from 0 to 1.75 paradoxically increased O(2) uptake (VO(2)) where a low mixed venous partial pressure of N(2)O [high N(2)O uptake (VN(2)O)] was specified. With rising mixed venous partial pressure of N(2)O, a threshold was observed where VO(2) began to fall, whereas VN(2)O began to rise with increasing VA/Q inhomogeneity. This phenomenon is a magnification of the concentrating effects that VO(2) and VN(2)O have on each other in low VA/Q compartments. During "steady-state" N(2)O anesthesia, VN(2)O is predicted to paradoxically increase in the presence of worsening VA/Q inhomogeneity.

Anesthesia↗
PubMed2005

Seventy-two hour gas exchange performance and hemodynamic properties of NOVALUNG iLA as a gas exchanger for arteriovenous carbon dioxide removal.

OBJECTIVE: Acute respiratory failure is complicated by acidosis and altered end-organ perfusion. NOVA-LUNG iLA is an interventional lung assist (ILA) device for arteriovenous carbon dioxide removal (AVCO2R). The present study was conducted to evaluate the device for short-term CO2 removal performance and hemodynamic response. METHODS: Six adult sheep received cannulation of the jugular vein and carotid artery. The ILA-AVCO2R circuit was placed on the sheep for 72 hours. Hemodynamics and PaCO2 were measured; CO2 removal was calculated while varying sweep gas flow rates (Qg), device blood flow rates (Qb), and PaCO2. RESULTS: Hemodynamic variables remained normal throughout the 72 hour study. CO2 removal increased with increases in Qg or Qb. Mean CO2 removal was 119.3 ml/min for Qb 1 L/ min, Qg 5 L/min, and PaCO2 40-50 mmHg. PaCO2 was directly proportional to CO2 clearance (R=0.72, p <0.001). CONCLUSION: NOVALUNG iLA can provide near total CO2 removal with Qb 1-2 L/min, Qg 5 L/min, and minimal flow resistance (3.88+/-0.82 mmHg/L/min). PaCO2 correlates with CO2 removal and is dependent on Qb and Qg.

Animals↗
PubMed1995

Is tracheal gas insufflation an alternative to extrapulmonary gas exchangers in severe ARDS?

Tracheal gas insufflation (TGI) of pure oxygen combined with mechanical ventilation decreases dead space and increases CO2 clearance. In the present study, TGI was used in six patients with ARDS who met extracorporeal membrane oxygenation criteria and who were severely hypoxemic and hypercapnic despite optimal pressure-controlled ventilation. This open clinical study aimed to investigate the effects of 4 L/min continuous flow of oxygen given via an intratracheal catheter. PaCO2 decreased from 108 +/- 32 to 84 +/- 26 mm Hg (p < 0.05), and no significant change in PaO2 (68 +/- 18 vs 96 +/- 43, p = 0.06). There was no change in airway pressures and hemodynamic variables. A slight increase in end-expiratory and end-inspiratory volumes with TGI possibly occurred, as seen on tracings from respiratory inductive plethysmography (Respitrace). We conclude that TGI improves tolerance of limited pressure ventilation by removing CO2, but it may induce changes in lung volumes that are not detected by ventilator measurements.

Adult↗
PubMed1996

Comparison and assessment of blood gas related quantities including base excess, the gas exchange indices, and temperature corrected pH/PO2/PCO2, as defined in approved NCCLS standard C12-A, using a computer simulation of input variables.

Blood gases and related quantities reported to clinicians have, since the earliest days, included both directly measured as well as calculated or estimated quantities. Some developed as substitutes for quantities that were or are difficult to measure routinely, others to explain relationships between older, difficult to measure quantities and newly measureable quantities, and still others attempt to better understand the physiology of the acid-base process. The net result is a plethora of acid-base and related quantities that may be reported by different blood gas systems. In an attempt to address the issue of which quantities have stood the test of usefulness over time, and further, to examine the optimum algorithm for use in quantification, the NCCLS has developed, through its consensus process, a recommended set of quantities and their quantifying algorithms. We have studied these quantities and compared them with some other recognized approaches and present our analysis in this report. The major conclusion is that among those quantities recommended, the NCCLS algorithms present the most sensible overall approach and that we would recommend their use as described so that the quantities can be most effectively applied clinically, without differences in final values occurring due solely simple algorithm differences.

Acid-Base Equilibrium↗
PubMed1994

Perfluorocarbon associated gas exchange (PAGE): gas ventilation of the perfluorocarbon filled lung.

BACKGROUND: Throughout most of the second half of this century, progress in respiratory life support was dominated by modernization of the mechanical ventilator. We have now entered an era in which the fundamental physiology of lung function can be manipulated to improve lung performance in hope of reducing morbidity and mortality and thereby decreasing the cost of intensive care. MAIN FINDINGS: Despite its almost alien technology, perfluorocarbon tidal liquid breathing is an effective means to support respiration in normal and surfactant deficient lungs. A second, technique, perfluorocarbon associated gas exchange (PAGE), has recently been shown effective in normal lungs and in several animal models of lung disease. Both techniques appear to improve pulmonary function when pulmonary surface tension is elevated. CONCLUSIONS: PAGE improves lung function and poses opportunities to reduce pulmonary morbidity and diminish the cost of intensive care.

Animals↗
PubMedDate not supplied

Environmental screening of acidic compounds based on capillary zone electrophoresis/laser-induced fluorescence detection with identification by gas chromatography/mass spectrometry and gas chromatography/high-resolution mass spectrometry.

This paper describes the application of capillary zone electrophoresis/laser-induced fluorescence detection (CZE/LIF) to the discovery of acidic compounds in environmental matrixes or the screening of extracts for acidic components. Published studies indicate that coal-derived materials contain a significant fraction of acidic compounds relative to materials derived from petroleum and shales. Such compounds may be useful as marker compounds for site assessment and source apportionment issues, and their identification may be important in toxicological and other health issues. We used deep-UV light from the frequency-doubled Ar ion laser at 244 and 257 nm to study extracts of samples. The CZE/LIF technique possesses good sensitivity and therefore overcomes one of the limitations of CZE with UV detection. The present work depends on high pressure/temperature solvent extraction of polynuclear aromatic hydrocarbon (PNA)-contaminated soil, followed by separation using CZE. The anionic analytes were separated by using borate or phosphate buffer (pH 9.2-12.3) after a chemical class separation. Samples were also characterized by gas chromatography/mass spectrometry (GC/MS) using full scans at low resolution, and elemental compositions were determined unequivocally by GC/high-resolution MS (GC/HRMS) using mass peak profiling (MPP). The similarity of low-resolution electron ionization mass spectra for a standard, 1-hydroxypyrene, and for a series of compounds in a contaminated-soil extract suggested that several types of phenolic and hydroxy-PNAs were present, including hydroxylated derivatives of fluorenes, fluoranthenes, and pyrenes. GC/HRMS using MPP confirmed the elemental compositions of the hydroxyfluorenes and hydroxypyrenes (and presumably hydroxyfluoranthenes) as [C13H10O] and [C16H10O], respectively. A new version of the MPP software was written for the Finnigan-MAT 900S-Trap and was similar to that developed previously for the VG 250SE. Inclusion of a calibration ion in addition to a lock mass ion in the multiple-ion detection descriptor provided errors of <1 ppm for the 3 partial profiles of the analytes. A mass resolution of 31,000 was used to resolve the analyte signals from interferences evident in the full M+1 and M+2 profiles in the case of the hydroxyfluorenes. Derivatization was also performed to form the tert-butyldimethylsilyl derivatives of phenolic hydroxy groups as a further confirmation of structure.

Acids↗
PubMed1976

Quantitative gas chromatography and gas chromatography-mass spectrometry of Cephalotaxus alkaloids.

Plants of the genus Cephalotaxus contaim many alkaloids, some of which have demonstrated antitumor activity. Analysis of crude alkaloid mixtures by gas chromatography provides quantitation of the active principles and other, non-active, alkaloids. Mass spectrometry is used to identify known alkaloids in extracts and to confirm the presence of previously unknown ones. Such data provide a means for predicting the biological activity of new plant accessions.

Alkaloids↗
PubMedDate not supplied

Overview of methods for the determination of trans fatty acids by gas chromatography, silver-ion thin-layer chromatography, silver-ion liquid chromatography, and gas chromatography/mass spectrometry.

trans Isomers of naturally occurring cis-unsaturated fatty acids are produced when liquid vegetable oils or marine oils are partially hydrogenated to produce margarine, shortenings, and other hardened-fat products. Isomeric trans fatty acids are also formed in the intestinal tract of ruminants, and they appear in small amounts in dairy products and ruminant meat. Currently, satisfactory analyses for the fatty acid profiles of fats containing trans fatty acids are obtained by gas chromatography (GC) using capillary columns coated with highly polar cyanosilicone stationary phases. In capillary GC methods, the key limitation has been the incomplete separation of trans-monoenoic acid isomers from their cis isomers; however, recent reports have demonstrated that improvements in separation are attainable with the use of 100 m columns. In these columns, there is very little overlap of cis and trans isomers. More accurate trans fatty acid analyses can be obtained by coupling GC with either silver-nitrate thin-layer chromatography or silver-nitrate liquid chromatography.

Chromatography, Liquid↗
PubMed2004

Determination of methyl tert-butyl ether (MTBE) in Chinese fuels by gas chromatography/mass spectrometry and gas chromatography/flame ionization detector.

A method was developed to determine the concentration of methyl tert-butyl ether(MTBE) in gasoline, diesel and heating oil by gas chromatography(GC) with mass spectrometry(GC-MS) or flame ionization detection (FID). The diluted gasoline was directly injected into the GC, and the complete separation of MTBE from co-eluting hydrocarbons was not required. GC/MS or GC/FID method can be used to analyze MTBE in different concentration range and have good consistency.

Carcinogens↗
PubMed1992

Skin manifestations of mustard gas. A clinical study of 535 patients exposed to mustard gas.

BACKGROUND: During the Iraq-Iran war (1980-1988), 535 patients who were exposed to mustard gas (one of the chemical warfare agents used by Iraq) were referred to our dermatology department. In this article, we have tried to review the skin manifestations of these patients. OBSERVATIONS: The skin lesions were of early or late onset. The early onset lesions consisted of erythema (76%), bulla (55%), and purpura (1.1%). These lesions were mostly found on the face and skin folds. The late-onset manifestations were pigmentation (20.4%) and desquamation (11.2%). Other complications were ophthalmic (85%), pulmonary (15%), and gastrointestinal (10%). Lymphopenia (7%) was the most serious laboratory disorder reported. Biopsy specimens of the lesions showed subepidermal bullae with mild dermal and epidermal necrosis. CONCLUSIONS: All patients were treated as for burns using sulfadiazine and furacine. All patients were cured in a period of 15 to 45 days. During a 6-month follow-up, no mortality was observed.

Adult↗