Headspace analysis toluene

HS-GC methods have equally been used for chromatographic analysis of residual volatile substances in PS [219]. In particular, various methods have been described for the determination of styrene monomer in PS by solution headspace analysis [204,220]. Residual styrene monomer in PS granules can be determined in about 100 min in DMF solution using n-butylbenzene as an internal standard for this monomer solid headspace sampling is considerably less suitable as over 20 h are required to reach equilibrium [204]. Shanks [221] has determined residual styrene and butadiene in polymers with an analytical sensitivity of 0.05 to 5 ppm by SHS analysis of polymer solutions. The method development for determination of residual styrene monomer in PS samples and of residual solvent (toluene) in a printed laminated plastic film by HS-GC was illustrated [207], Less volatile monomers such as styrene (b.p. 145 °C) and 2-ethylhexyl acrylate (b.p. 214 °C) may not be determined using headspace techniques with the same sensitivities realised for more volatile monomers. Steichen [216] has reported a 600-fold increase in headspace sensitivity for the analysis of residual 2-ethylhexyl acrylate by adding water to the solution in dimethylacetamide. 

Soil spiked with trichloroethylene and toluene was analysed using a gas chromatograph equipped with a PT concentrator that was found to be replaceable by a headspace unit in order to simplify the overall assembly. The headspace analysis of soil samples was found to be restricted by incomplete desorption of the contaminants in soil-water mixtures this shortcoming, however, was effectively overcome by the addition of methanol. Henry s law constants for volatile organics in methanol must previously be determined if the method is to be applied to soils [142]. A comparison of the performance of static and dynamic (PT) headspace modes in the determination of nine VOCs in five different soils revealed poor PT recoveries in relation to those of static headspace (which ranged from 68 to 88%) the latter, however, required longer development times [143],... 

A water sample is analyzed for traces of benzene using headspace analysis. Samples and standards are spiked with a fixed amount of toluene as internal standard. The following data are obtained ... 

Hagman and co-workers [3] and Schmidt and co-workers [4] used dynamic headspace analysis to study volatiles in polypropylene-polyethylene copolymers and PVC and polyethylene terephthalate. In the latter method [3], volatiles from PET and PVC were collected and separated by open tubular GC. Other solid polymer headspace methods discussed include hexane, tridicane and butylated hydroxytoluene in polypropylene [5], vinyl chloride, vinyl acetate, acetaldehyde and water in vinyl and acrylic polymers and polyolefins [6], ethyl acetate and toluene in laminated polyolefins [7], miscellaneous volatiles in polymers [8] and solvents retained in plastic films [9-12]. 

In instances where the chemical identity of some or all of the volatiles present in a polymer are not known it is possible to obtain the required information by the application of this technique. Thus, workers at Hewlett Packard [3] used headspace analysis mass spectroscopy (MS) to identify six volatiles in styrene-acrylonitrile-maleic anhydride teropolymer (benzene, toluene, ethylbenzene, styrene, aromatics, and maleic anhydride). 

Comparable ratios are obtained in the analysis of a solid sample, for example, the analysis of residual solvents in a technical product. A run using the P T technique and 10 mL of sample at 150 °C gave a recovery of 63% for toluene. The sample contained 1.6 ppm, which corresponds to a quantity of 101 ng. The partition coefficient in the static headspace technique at 150 °C (for a sample of 1 g) is 95. The quantity of residual solvent in 19 mL of headspace is therefore 17 ng. For an injection of 0.5 mL, 0.4 ng are injected. The quantity injected is therefore smaller by a factor of 250 than that in the P T analysis. Furthermore, the reproducibility of this analysis was 7% for the P T technique and 32% for the static headspace analysis (RSD). 

Several approaches are used to isolate and eoneentrate volatile analytes from waste samples for subsequent measurement. Some of these based on headspace analysis involve evaporation of volatile substanees into the space above the sample (headspace) in a closed container. Method 5021, Volatile Organic Compounds in Soils and Other Solid Matrices Using Equilibrium Headspace Analysis, is used to isolate volatile organic compounds, such as benzene, bromomethane, chloroform, 1,4-dichlorobenzene, dichloromethane, styrene, toluene, vinyl chloride, and the xylene isomers, from soil, sediment, or solid waste samples for determination by gas chromatography or gas chromatography/mass spectrometry. 

The principle of headspace sampling is introduced in this experiment using a mixture of methanol, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, benzene, toluene, and p-xylene. Directions are given for evaluating the distribution coefficient for the partitioning of a volatile species between the liquid and vapor phase and for its quantitative analysis in the liquid phase. Both packed (OV-101) and capillary (5% phenyl silicone) columns were used. The GG is equipped with a flame ionization detector. 

Analysis of a group of smokeless powders of known composition showed that the main components of their headspace vapor were acetone, toluene and limo-nene the concentration of nitroglycerin (NG) was relatively low. A series of... 

Fig. 5.2. Gas chromatography (GC) and electroantennography (EAG) analysis of male Manduca sexta antennal responses to floral volatiles from the night blooming cactus Peniocereus greggii. The upper trace is a flame ionization detection (FID) chromatogram of floral headspace odors separated on a carbowax GC column, while the lower trace is a simultaneous recording of summed antennal action potentials elicited by individual compounds as they elute. The largest absolute responses followed methyl benzoate, methyl salicylate, and benzyl alcohol (peaks 3-5, respectively). Note the poor responses (circled) to benzaldehyde and benzyl benzoate (peaks 2, 6) and the disproportionately higher responses (bold arrows) to methyl salicylate and benzyl salicylate (peak 7) relative to their peak areas. Peak 1 is the internal standard (toluene) remaining unnumbered peaks are ambient contaminants.

Figure 8.13 Analysis of o-xylene and BTEX (in water) using solid-phase microextraction (a) direct SPME fibre mode (b) headspace SPME fibre mode (c) results obtained for o-xylene using mode (a) (d) results obtained for BTEX using mode (b) , no stirring IH, with stirring , with stirring, plus salt , benzene , toluene a, ethylbenzene , m-, p-xylene(s) x, o-xylene [4] (cf. DQ 8.11).

Generally, GC is a very suitable technique for the analysis of these volatile substances and the definitive proof of exposure to them is their detection in biological fluids and tissues. All the commonly abused solvents can be detected in the headspace from 200 pi of blood. Toluene could be detected by MS in the breath of known glue sniffers up to 4 days after the last episode. GC and GC-MS were used to determine toluene in various tissues and blood in a... 

Headspace sampling is an excellent technique for the analysis of compounds that produce, odors in many commercial products, such as plastics, rubbers, paints, resins, etc. Interfacing of a headspace GC with a mass spectrometer provides valuable information for the identification of such components. Figure 9 shows the output from head space-GC analysis of residual benzene and toluene in polymeric material. 

Figure 9 GC chromatogram trace analysis of benzene and toluene in polymer by headspace GC-FID.

Abbreviation for the analysis of the benzene, toluene, ethylbenzene and xylene isomers group of aromatics, mostly by headspace sample analysis. 

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