W. Bertsch

Trace analysis of organic volatiles in water by gas chromatography-mass spectrometry with glass capillary columns

Traces of volatile organic materials in water have been concentrated by gas phase stripping and adsorption onto a porous polymer. A simple all-glass sampling device is proposed which allows efficient concentration at elevated temperatures. Sample transfer from absorbent into a gas chromatographic column is effected by a simple one-step procedure involving heat desorption. The capacity of the absorbent has been determined for a number of model substances which are found in water. Under the sampling conditions used, compounds being less volatile than benzene are usually quantitatively retained, with some exceptions. Separations were effected with highly efficient glass capillary columns. Water samples, collected from a small number of locations, included both tap water and untreated waters. A number of volatiles have been determined by gas chromatography-mass spectrometry in drinking water and in a river which flows through an industrialized area. The drinking water examined contains a large number of chlorinated and brominated compounds whereas the river water is largely free from this class of substances. Derivatives of camphor and terpenes have been identified in this particular river.

Collection and analysis of trace organic emissions from natural sources

Abstract A study was undertaken to develop practical techniques for measurement of hydrocarbons and oxygenated volatiles in rural areas. A limited number of rural and urban samples were taken to demonstrate the general applicability of the method. Sampling locations were selected in a large forest at a distance of about 35 miles from a heavily populated area. It turned out that this distance was not sufficient to escape the urban influence and compounds typical of urban activities were found at dilute concentrations. The sampling method is based on adsorption of the trace organics on suitable adsorbents with subsequent thermal elution. Besides Tenax GC and Carbopack BHT the use of a new carbonaceous adsorbent, Ambersorb XE-340 (Rohm and Haas, Philadelphia, Pa., U.S.A.), was investigated. In preliminary experiments, this material had shown very good adsorption properties for low molecular weight compounds. The analysis of the volatile compounds was performed by gas chromatography-mass spectrometry with both metal and glass capillary columns. It was found that olefins, terpenes and other thermally labile compounds adsorbed on such materials were not altered even when stored over long periods of time. In general, the amount of volatiles found in rural air were 10–500 times lower than the corresponding levels in urban atmospheres, the lowest levels being found during the winter season. Semiquantitative data were obtained for some major compounds from rural areas. The level of organics strongly depends on season and meteorological conditions. Characteristic substances indigenous to plant life have been identified. Besides terpenes, a number of lower alcohols and esters have been found. Preliminary data are presented for a limited number of samples. Further studies are necessary to characterize and quantitate completely natural organic emissions.

Analysis of in situ methylated microbial fatty acid constituents by curie-point pyrolysis—gas chromatography—mass spectrometry

Abstract A newly developed Curie-point pyrolyzer has been used to analyze microbial fatty acid constituents. The pyrolysis was carried out on ferromagnetic wires, which were loaded into the gas chromatographic injector—pyrolyzer via a retractable Pyrex glass tube. Fatty acid methyl esters were obtained by in situ methylation of the free and glycerol bound fatty acids with trimethylanilinium hydroxide. The procedure was applied sucessfully to whole microorganisms. There was good agreement between the fatty acid methyl ester profiles from the whole-cell pyrolysis and from the lipid extracts of the corresponding organisms.

A Comprehensive Sample Preparation Scheme for Accelerants in Suspect Arson Cases

This study represents a critical comparison of adsorbent based heated headspace methods for the enrichment of volatiles from fire debris. A dynamic and a static method, based on charcoal adsorption and solvent extraction are compared to the solid phase micro extraction (SPME) procedure. The SPME method has been optimized in respect to fiber type, sampling time, sampling temperature, analyte concentration and the effects of water. Collection efficiencies were evaluated for a variety of accelerant types, ranging from methanol to diesel fuel. The minimum detectable quantity for each of the methods is within an order of magnitude for most accelerant types. We propose a two step method based on SPME with two different fibers. Polar and water soluble accelerants such as ethanol and light petroleum distillates are most effectively enriched at low temperature on Carboxen™, a newly developed high capacity fiber which contains a carbon based adsorbent. Low volatility accelerants such as diesel fuel can be recovered on a methylpolysiloxane type fiber at elevated temperature. Limitations of currently used sample preparation methods are discussed.

Determination of novolac resin thermal decomposition products by pyrolysis-gas chromatography-mass spectrometry

Abstract Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was used to identify the major volatile components produced by pyrolysis of a novolac resin. This resin is frequently used in the metal casting industry as a binder for sand molds. Quantitative analysis data of the pyrolysis products can serve as a model for the foundry industry to predict the amount of volatile organic compounds (VOCs) produced before actually carrying out the casting process. This allows the industry to comply with the Clean Air Act Amendments (CAAA) regarding the emissions of hazardous air pollutants (HAPs).

Volatiles from carpet: A source of frequent misinterpretation in arson analysis

Abstract Carpet and carpet padding are frequently submitted to laboratories for the analysis of residual accelerant in suspect arson cases. Charring and pyrolysis of the above matrixes produces volatiles that can cause interferences with some accelerants, most notably gasoline. A study was conducted to evaluate the interference potential of pyrolysis products obtained from simulated fire debris samples and from samples collected in the field. It was found that variable amounts of alkylbenzenes and naphthalenes are produced, along with large quantities of styrene and alkylstyrenes. Small amounts of higher-molecular-mass aromatic hydrocarbons are also generated but no alkanes or alkenes appeared. Since aromatic hydrocarbons are the major diagnostic components in gasoline, a potential interference is indicated. Careful observation of patterns within each group of isomers is required to rule out interferences. The distribution of alkylbenzenes in gasoline is quite different from the patterns produced by pyrolysis. Guidelines are proposed to distinguish between petroleum-based aromatic hydrocarbons and those derived from the pyrolysis of carpet/carpet padding. Mass fragmentography was found to be particularly useful toward the discrimination of interferences.

Gas chromatographic-mass spectrometric evaluation of exhaled tobacco smoke.

The impact of cigarette smoking on the distribution of organic substances in ambient air has been determined for the intermediate volatility range. A simple sampling procedure was employed, involving gas-solid adsorption onto an organic polymer followed by direct thermal elution onto a glass capillary column. Aliphatic and substituted aromatic hydrocarbons are predominant in urban atmospheres. Depending on location and weather conditions the total concentration of such volatiles can differ by as much as a factor of 20. This high background variation makes it difficult to analyze for trace substances with low odor threshold values, such as encountered in cigarette smoke. Standard cigarettes were smoked in a relatively small room, having no air filtration system. Air samples of approximately 3.51 were taken. The amount of volatiles added to air by cigarette smoking is unsignificant. Substances were analyzed and identified by gas chromatography and gas chromatography-mass spectrometry with glass capillary columns. Many compounds reported in cigarette smoke condensate have been confirmed.

Characterization of coal-derived fluids by capillary column gas chromatography-mass spectrometry

Abstract A coal-derived fluid has been analyzed by high-resolution gas chromatography—mass spectrometry with glass capillary columns, both before and after li

Insecticidal volatiles from the marigold plant (genustagetes). Effect of species and sample manipulation

SummaryVolatiles from three species of the genustagetes, commonly called marigold have been isolated and characterized. Simultaneous steam distillation extractions (SSDE) produced consistently extracts of higher insecticidal activity than Soxhlet extractions. Methylene chloride was the best solvent. Volatiles isolated from theminutae species showed higher activity than those frompatula anderecta. Comparison of extracts from the flower, foliage and roots of the plant showed that most of the activity is located in the flower. The volatiles are highly effective toward both larvae and adult mosquitoes.

A novel micro-technique for the analysis of the cuticular hydrocarbons of insects

Abstract Using a pyroprobe, the cuticular hydrocarbon profile of Solenopsis richteri workers was examined by capillary column gas chromatography. This sampling procedure was compared to the more conventional solvent extraction methods. It proved to be faster, more sensitive and selective, and required no solvents. The pyroprobe method routinely generates data from a single insect specimen [or even part(s) of an insect], whereas the information obtained from the solvent extraction methods is usually an average from a pooled sample. Although solvent extraction can be performed on a single insect, the purity of the solvent and the sample workup become increasingly critical.