Determination of partition coefficients by automatic equilibrium headspace gas chromatography by vapor phase calibration

Summary Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of vapor phase calibration —VPC where an external vapor standard is used to calibrate the concentration of the volatile analyte in the headspace, while the concentration in the sample is found from the difference in the total amount in the vial. This technique is described in detail for 2-butanone in water. Finally, the water-air partition coefficients of several selected volatile compounds at different temperatures are listed together with their temperature functions.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Comparative studies of electron-impact (EI) and field ionization (FI) mass spectra of pentaerythritol derivatives

The EI Mass spectra of the polyfunctional pentaerythritol derivatives show that the molecular ions [M]⁺· exhibit extensive ion fragmentation. No Information about [M]⁺·. can be obtained. In Contrast to this, the FI Mass spectra of these compounds show intense [M]⁺· and/or [M + 1]⁺, and a characteristic ion at m/e 31, which is assumed to be the oxonium ion \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_2 = \mathop {\rm O}\limits^ + {\rm H} $\end{document}. Because of surface adsorption and field attraction, FI mass spectrometry presents a serious problem in quantitative analysis of a mixture containing compounds with quite different degrees of polarization.     

A routine method for the determination of the TVOC content in wallcoverings using headspace gas-chromatography

A method for the fast routine analysis of the total content of volatile organic compounds in wallcoverings and paper products was developed, using headspace gas-chromatography for quantification. 57 wallcoverings of different types were investigated. Typical components were toluene, methyl-ethyl ketone, methyl-iso-butyl ketone, n-butyl acetate and iso-butyl acetate, all compounds being used as industrial solvents. The TVOC concentrations are calculated in toluene-carbon equivalents and ranged from 0.31 g/g to 1789 g/g with an average value of 123.22 g/g and a median of 20.37 g/g. To obtain an estimation of VOC-concentrations in indoor air, 10 selected wallcoverings were also analyzed in a 1 m³ climate test chamber. A correlation between headspace data and chamber concentrations could not be observed, which might be a result of increased analytical uncertainties at low emission rates under chamber conditions.     

Matrix effects of leachates in the determination of volatile priority pollutants by headspace analysis

Summary In order to investigate the matrix effects of a hazardous waste landfill leachate in the analysis of priority pollutants by headspace gas chromatography, spiking experiments were performed (a) with the untreated leachate, (b) with the leachate after separation of oil and (c) with blanc water samples as a reference. A standard mixture containing volatile chlorinated hydrocarbons, benzene and alkylated benzenes (100–200 g) were spiked into 50 ml-samples of (a)–(c). The samples were thermostated at 40°C for 20 min and analyzed by headspace GC. Serious matrix effects were observed for all reference compounds, resulting in significant enhancement or depression of the corresponding peak areas compared with the spiked water control samples. The data sets are discussed with respect to the contents of leachate oil and chloride. From the findings of this study, recommendations for the application of headspace analysis to leachates are given.     

Use of a gas-sensor array for detecting volatile organic compounds (VOC) in chemically induced cells

An application of gas sensors for rapid bioanalysis is presented. An array of temperature-modulated semiconductor sensors was used to characterize the headspace above a cell culture. Recombinant Saccharomyces cerevisiae yeast cells, able to respond to 17-estradiol by producing a reporter protein, were used as a model system. Yeast cells had the DNA sequence of the human estrogen receptor stably integrated into the genome, and contained expression plasmids carrying estrogen-responsive sequences and the reporter gene lac-Z, encoding the enzyme -galactosidase. The sensor-response profiles showed small but noticeable discrimination between cell samples induced with 17-estradiol and non-induced cell samples. The sensor array was capable of detecting changes in the volatile organic compound composition of the headspace above the cultured cells, which can be associated with metabolic changes induced by a chemical compound. This finding suggests the possibility of using cross-selective gas-sensor arrays for analysis of drugs or bioactive molecules through their interaction with cell systems, with the advantage of providing information on their bioavailability.     

A gas chromatographic assay for quantitative analysis of volatiles in solid materials by discontinuous gas extraction

Summary A method has been developed for the quantitative analysis of volatile compounds in solid samples. The method is based on a stepwise gas extraction of the volatiles with subsequent analysis of the extracted material and is termed discontinuous gas extraction. Any quantitative analysis requires an exhaustive extraction, which, however, is often too time-consuming for routine analysis. It is shown how the total amount of each volatile compound can be calculated from only a few extractions. Such a calculation is possible because for analytical purposes it is the information of the extraction process and not the extracted material that is needed. This method is useful for samples which are insoluble, such as certain polymers or residual solvents in printed foils, and which cannot be analyzed quantitatively by headspace gas chromatography, since no calibration solution can be prepared. It is further shown how discontinuous gas extraction can also be used to calibrate headspace analysis. Thus, both methods combine well together in that discontinuous gas extraction provides the accuracy while the headspace analysis gives convenience and speed of sample throughput, particularly if carried out with an automated headspace analyzer.     

Gas chromatography-mass spectrometry with solid-phase microextraction method for determination of methyl salicylate and other volatile compounds in leaves of<Emphasis Type="Italic"> Lycopersicon esculentum</Emphasis>

Methyl salicylate (MeSA) in many plants is a important signaling compound, which plays an important role in a pathogen-induced defense response. In this paper, gas chromatography-mass spectrometry (GC-MS) with headspace solid-phase microextraction (HS-SPME) was developed for determination of MeSA and other volatile compounds in leaves of a tomato plant (Lycopersicon esculentum). Tomato leaves were ground under liquid nitrogen and sampled by HS-SPME, with a 100 m polydimethylsiloxane fiber, and finally analyzed by GC-MS. Eighteen compounds in the leaves of tomato plant infested by tobacco mosaic virus (TMV) were separated and identified, among them MeSA, which was quantitatively analyzed by the standard addition method. MeSA concentrations higher than 2.0 g g^–1 fresh weight accumulated in leaves of TMV-infested tomato plant as the defense response to TMV. A similar concentration of MeSA in the leaves of MeSA-treated tomato plant was also found. No MeSA in leaves of control tomato plant was detected. These findings suggest that MeSA might be a signaling compound in the tomato plant response to TMV. The present method for determination of MeSA required only simple sample preparation and no organic solvent, and provided an excellent relative standard deviation of less than 5.0% and a low detection limit of 10 ng g^–1 fresh weight for MeSA. These results show that GC-MS-HS-SPME is a simple, rapid and sensitive method for determination of MeSA and other plant-signaling compounds in plant tissues.     

Die geruchsintensivsten Inhaltsstoffe des ostindischen Sandelholzöles

The most odour intensive constituents of east indian sandal wood oil are -santalol, -santalal and -santalene. This has been proved by a thorough GLC-investigation in combination with the sniffing technique of seven fractions of this highly priced essential oil, which have been obtained by TLC on silica-cellulose plates with simultaneous organoleptic evaluation. Using the headspace analysis these results could be confirmed and further the distribution of the main odour components was obtained in headspace at 37° and 80°.

Herrn Prof. DDr. h. c.K. Kratzl in dankbarer Verehrung mit den besten Wünschen zum 70. Geburtstag gewidmet.     

Comparative Evaluations of Mass Spectral Databases

This Communication presents a statistical analysis of the distributions of the National Institute of Standards and Technology/Environmental Protection Agencyj Mass Spectrometry Data Center Mass Spectral Database and the Wiley Registry of Mass Spectra according to sizes (peaks per spectrum) of spectra. The differences in the distributions are explained in terms of the different philosophies under which the two databases were built. The Wiley Registry is a collection that attempts to include all available spectra, including spectra of unique compounds derived from the literature. The NIST collection selects primarily spectra of interest for chemical analysis.     

Liquid chromatography of phenolic compounds in natural water using on-line trace enrichment

Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 g 1^–1 and 20 l^–1 and limits of determination between 0.5 g l^–1 and 1 g l^–1 are obtained.     

Synthesis of New Thieno[2,3-b:5,4-c']dipyridines

We describe the formation of thieno[2,3-b:5,4-c]dipyridines from 5,6-dihydropyridine-2(1H)-thiones. The two-step reaction mechanism was revealed by isolation of an intermediate. The oxo and thioxo groups of the obtained tricyclic compounds were hydrogenated selectively. The structures of all new compounds were elucidated by NMR experiments.     

A method of calculating mass absorption coefficient of beta-particles

A method to obtain mass absorption coefficients of -articles in multielement substances is described. This method is based on a theoretical formula of the mass absorption coefficient. Mass absorption coefficient of compounds calculated by this method are in good agreement with earlier measurements and methods of computation.     

Simple Analysis of Amphetamines in Human Whole Blood and Urine by Headspace Capillary Gas Chromatography with Large Volume Injection

Summary A very simple method for the analysis of methamphetamine and amphetamine in human whole blood and urine by headspace gas chromatography (GC) has been presented. It neither needs solid-phase microextraction nor cryogenic trapping devices, but only a conventional capillary GC instrument with flame ionization detection (FID). The two special points to be mentioned in this method are the in-matrix derivatization of amphetamines for vaporization and the capability of injection of as large as 5 mL of the headspace vapor into a GC instrument in the splitless mode for sensitive detection. After heating a whole blood or urine sample containing amphetamines, -methylbenzylamine (internal standard, IS) and heptafluoro-n-butyryl chloride under alkaline conditions in a 7.0-mL vial at 90 °C for 20 min, 5 mL of the headspace vapor was drawn with a glass syringe and injected into the gas chromatograph. During injection the column was at 40 °C to trap the analytes, and then the oven temperature was programmed up to 320 °C. Sharp peaks were obtained for each analyte and IS, and only a relatively small number of background impurity peaks for the whole blood and urine samples. The detection limits for each amphetamine were estimated to be 0.1 g mL^–1 for whole blood and 0.03 g mL^–1 for urine. Precision and linearity were also tested to confirm the reliability. Methamphetamine and amphetamine could be determined from whole blood and urine obtained at autopsy in three methamphetamine poisoning cases. The identity of each peak appearing in the gas chromatograms was confirmed by GC/mass spectrometry.     

Reactions of tellurium tetrahalides with 1,5- and 1,6-diolefins and their derivatives

1,4-Dihalo-substituted tellurolanes were obtained by reaction of tellurium tetrabromide and tetrachloride with 1,5-hexadiene, and the corresponding six-membered heterocyclic compounds with a tellurium atom in the ring were obtained with 1,6-diolefins.Communication IV from the series Organic Selenium and Tellurium Compounds. See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1212–1214, September, 1978.     

Single-walled carbon nanohorns immobilized on a microporous hollow polypropylene fiber as a sorbent for the extraction of volatile organic compounds from water samples

We have evaluated the behavior of single-walled carbon nanohorns as a sorbent for headspace and direct immersion (micro)solid phase extraction using volatile organic compounds (VOCs) as model analytes. The conical carbon nanohorns were first oxidized in order to increase their solubility in water and organic solvents. A microporous hollow polypropylene fiber served as a mechanical support that provides a high surface area for nanoparticle retention. The extraction unit was directly placed in the liquid sample or the headspace of an aqueous standard or a water sample to extract and preconcentrate the VOCs. The variables affecting extraction have been optimized. The VOCs were then identified and quantified by GC/MS. We conclude that direct immersion of the fiber is the most adequate method for the extraction of VOCs from both liquid samples and headspace. Detection limits range from 3.5 to 4.3 ng L^?1 (excepted for toluene with 25 ng L^?1), and the precision (expressed as relative standard deviation) is between 3.9 and 9.6 %. The method was applied to the determination of toluene, ethylbenzene, various xylene isomers and styrene in bottled, river and tap waters, and the respective average recoveries of spiked samples are 95.6, 98.2 and 86.0 %.

Synthesis and bio‐activity of novel iminophosphoranes

The title compounds ( 5a‐j ) were synthesized by a two step process. 4‐Chlorophenyl and bis(2‐chloroethyl) amino‐dibromophosphites ( 1a and 1b ) were reacted with 1,8‐diaminonaphthalene ( 2 ) to form the diazaphosphinines ( 3a and 3b ). They were further reacted with different alkyl azides ( 4a‐e ) in THF at 50‐55 °C under N₂ atmosphere to afford the corresponding iminophosphoranes ( 5a‐j ). Their structures were established by elemental analysis, IR, ¹H, ¹³C, ³¹P NMR and Mass spectral data. All of them exhibited moderate antibacterial activity.     

Synthesis of β-(9-purinyl)alanines

The corresponding 1-(6-substituted-9-purinyl)-2,2-diethoxyethanes were obtained by alkylation of 6-substituted purines with 1-bromo-2,2-diethoxyethane. Subsequent transformations of a large portion of the acetals gave 2-(6-substituted-9-purinyl) acetaldehydes, from which -(6-substituted-9-purinyl)alanines were obtained by the cyanohydrin synthesis. The classification of the compounds as N(₉)-substituted purine derivatives was proved by means of UV spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1561–1566, November, 1972.     

Mass-spectral Study of 9-[α(β,γ)-Picolylidene]-1(4)-azafluorenes

A mass-spectral study was carried out on the behavior of the Z- and E-isomers of 9-picolylideneazafluorenes. A possible mechanism for the elimination of a hydrogen atom from the M⁺ ion of the Z- and E-isomers of 1(4)-azafluorene derivatives was examined. Mass spectrometry permitted a distinction between compounds isomeric relative to the position of the nitrogen atom in the azafluorene fragments and also the Z- and E-isomers of picolylidene derivatives of 1- and 4-azafluorenes possessing - and -pyridyl substituents.     

Synthesis of New Thieno[2,3-<Emphasis Type="Italic">b</Emphasis>:5,4-<Emphasis Type="Italic">c</Emphasis>′]dipyridines

Summary. We describe the formation of thieno[2,3-b:5,4-c]dipyridines from 5,6-dihydropyridine-2(1H)-thiones. The two-step reaction mechanism was revealed by isolation of an intermediate. The oxo and thioxo groups of the obtained tricyclic compounds were hydrogenated selectively. The structures of all new compounds were elucidated by NMR experiments.Received December 17, 2002; accepted December 20, 2002 Published online June 2, 2003     

Headspace mass spectrometry methodology: application to oil spill identification in soils

In the present work we report the results obtained with a methodology based on direct coupling of a headspace generator to a mass spectrometer for the identification of different types of petroleum crudes in polluted soils. With no prior treatment, the samples are subjected to the headspace generation process and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of volatiles in the sample analysed. The mass spectrum corresponding to the mass/charge ratios (m/z) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization of the samples. The signals obtained for the different samples were treated by chemometric techniques to obtain the desired information. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation are required. The method is rapid, simple and, in view of the results, highly promising for the implementation of a new approach for oil spill identification in soils. Figure PCA score plots illustrate clear discrimination of types of crude oil in polluted soil samples (e.g. results are shown for vertisol)