Purge and trap method

Gas Chromatography. Gas chromatography is a technique utili2ed for separating volatile substances (or those that can be made volatile) between two phases, one of which is a gas. Purge-and-trap methods are frequently used for trace analysis. Various detectors have been employed in trace analysis, the most commonly used being flame ioni2ation and electron capture detectors. 

Purge-and-trap methods have also been used to analyze biological fluids for the presence of trichloroethylene. Breast milk and blood were analyzed for trichloroethylene by purging onto a Tenax gas chromatograph to concentrate the volatiles, followed by thermal desorption and analysis by GC/MS (Antoine et al. 1986 Pellizzari et al. 1982). However, the breast milk analysis was only qualitative, and recoveries appeared to be low for those chemicals analyzed (Pellizzari et al. 1982). Precision (Antoine et al. 1986) and sensitivity (Pellizzari et al. 1982) were comparable to headspace analysis. 

Analysis of environmental samples is similar to that of biological samples. The most common methods of analyses are GC coupled to MS, ECD, a Hall s electrolytic conductivity detector (HECD), or a flame-ionization detector (FID). Preconcentration of samples is usually done by sorption on a solid sorbent for air and by the purge-and-trap method for liquid and solid matrices. Alternatively, headspace above liquid and... 

Analysis of soils and sediments is typically performed with aqueous extraction followed by headspace analysis or the purge-and-trap methods described above. Comparison of these two methods has found them equally suited for on-site analysis of soils (Hewitt et al. 1992). The major limitation of headspace analysis has been incomplete desorption of trichloroethylene from the soil matrix, although this was shown to be alleviated by methanol extraction (Pavlostathis and Mathavan 1992). 

Heikes DL, Hopper ML. 1986. Purge and trap method for determination of fumigants in whole grains, milled grain products, and intermediate grain-based foods. J Assoc Off Anal Chem 69 990-998. 

The Bellar et al. [219] purge and trap method has been applied to the determination of vinyl chloride in seawater. Using the Hall electrolytic conductivity detector, no response was obtained for the acetone used to prepare the vinyl chloride standard solution. 

Purge, adsorption processes, 7 613, 614 Purge-and-trap methods... 

Few well characterized, validated methods are available for the determination of w-hexane in blood. A purge-and-trap method for volatiles has been developed and validated by researchers at the Centers for Disease Control and Prevention (CDC) (Ashley et al. 1992, 1994). Extension of the method to include /7-hexane should be possible. Current analytical methods utilize capillary GC columns and MS detection to provide the sensitivity and selectivity required for the analysis. Detection limits are in the low ppb range (Brugnone et al. 1991 Schuberth 1994). Headspace extraction followed by GC analysis has also been utilized for the determination of /7-hexanc in blood (Brugnone et al. 1991 Michael et al. 1980 Schuberth 1994) however, very little performance data are available. 

Charles and Simmons [18] obtained overall recoveries of 38%, 48% and 54% respectively, for chloroform, trichloroethylene and chlorobenzene from sediments using purge and trap methods. 

Methyltin compounds were determined in complex samples by a sensitive purge and trap method at detection limits of 3-5pg with 6-18% precision. The method is selective and specific and free from most interferences. 

APHA. 1985a. Halogenated methanes and ethanes by purge and trap-method 514. In Standard methods for the examination of water and wastewater. 16th ed. American Public Health Association, Washington, DC, 591-602. 

In general, zero-headspace procedures are employed when the concentrations of volatiles in the soil are relatively low, and solvent extraction methods are used for more polluted soils. Irrespective of which procedure is used, quantitation of volatiles in soil is subject to serious errors if sufficient care is not taken with the sampling operation. Although direct purge-and-trap methods are frequently advocated for the determination of volatiles in samples collected by zero-headspace procedures, there are certain problems associated with this technique. Caution is advised since the procedure really collects only that fraction of the volatile that exists in a free form within the soil pore spaces or is at least in a facile equilibrium with this fraction. 

Dibromoethane is usually isolated from aqueous media by the purge-and-trap method or liquid-liquid extraction. GC/ECD or GC/MS is the technique employed for measuring... 

Sample collection and preparation for the analysis of 1,2-dibromoethane in foods includes the purge-and-trap method, headspace gas analysis, liquid-liquid extraction, and steam distillation (Alleman et al. 1986 Anderson et al. 1985 Bielorai and Alumot 1965, 1966 Cairns et al. 1984 Clower et al. 1985 Pranoto-Soetardhi et al. 1986 Scudamore 1985). GC equipped with either ECD or HECD is the technique used for measuring 1,2-dibromoethane in foodstuffs at ppt levels (Clower et al. 1985 Entz and Hollifield 1982 Heikes and Hopper 1986 Page et al. 1987 Van Rillaer and Beernaert 1985). 

Amaral OC, Olivella L, Grimalt JO. 1994. Combined solvent extraction-purge and trap method for the determination of volatile organic compounds in sediments. J Chromatogr A 675(1) 177-187. 

Analysis of Trihalomethanes in Drinking Water by the Purge and Trap Method... 

A number of other compounds have been concentrated and measured using the purge and trap method, but no recovery data for these is available. These compounds include chloromethane, bromoethane, chloroethane, 1,2-dichloropropane, trans-1,3-dichloropropene-1, cis-l,3-dlchloropropene-l,... 

EPA. 1981. The analysis of aromatic chemicals in water by the purge and trap method-method 503.1. Cincinnati, OH. U.S. Environmental Protection Agency, Office of Research and Development, Environmental Monitoring and Support Laboratory. 

Heikes, D.L. (1987) Purge and trap method for determination of volatile halocarbons and carbon disulfide in table-ready foods. J. Assoc, off. anal. Chem., 70, 215-226... 

The purge-and-trap method (see Section 6.4) is a common method to enrich volatile organic compounds from water samples. In your apparatus, you purge a 1 L water sample with a gas (air) volume flow of 1.5 L gas per minute at a temperature of 25°C. The compounds that you are interested in include tetrachloroethene, chlorobenzene and methyl-t-butylether (MTBE). Calculate the time required to purge 90% of each compound from the water. Any comments How much time would you save if you would increase the temperature from 25°C to 35°C What could be a problem when raising the temperature too much You can find all necessary data in Appendix C and in Table 6.3. 

Three purge and trap methods are used to determine 29 halocarbons (Method 601), seven aromatics (Method 602, including four of the halo-carbons), and acrolein and acrylonitrile (Method 603). The three methods are distinctly different in the sorbent trap materials, GC columns, and... 

In addition to the THM methods, EMSL-Cincinnati has developed purge and trap methods for selected halogenated (29) and aromatic (30) compounds that are considered to be chemical indicators of industrial contamination. The methods are applicable to 47 halogenated compounds (Method 502) and 33 compounds that have ionization potentials less than 10.2 eV and that are aromatic or contain a doubly bonded carbon (Method 503). Seven of these compounds are halogenated and are also included in the method for halogenated compounds. Another method, Method 524 (31), provides for GC-MS determination of 28 purgeable volatiles. Single laboratory precision and accuracy data for these compounds are provided in the EMSL methods. 

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