Trace analysis of halocarbons in water; Direct aqueous injection with electron capture detection

Grob, Konrad; Habich, A.

doi:10.1002/jhrc.1240060103

Cited by 53 publications

(1 citation statement)

References 10 publications

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“…Following the approach described by Grob ( , ), most applications of DAI employ on-column injection to minimize peak tailing and nonpolar columns to minimize retention of water ( − ). Recently, DAI onto a nonpolar column was investigated for the analysis of a broad range of organic compounds in petroleum-contaminated groundwater ().…”

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confidence: 99%

Method for Determination of Methyltert-Butyl Ether and Its Degradation Products in Water

Church

Isabelle

Pankow

et al. 1997

Environ. Sci. Technol.

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An analytical method is described that can detect the major alkyl ether compounds that are used as gasoline oxygenates (methyl tert-butyl ether, MTBE; ethyl tert-butyl ether, ETBE; and tert-amyl methyl ether, TAME) and their most characteristic degradation products (tert-butyl alcohol, TBA; tert-butyl formate, TBF; and tert-amyl alcohol, TAA) in water at sub-ppb concentrations. The new method involves gas chromatography (GC) with direct aqueous injection (DAI) onto a polar column via a splitless injector, coupled with detection by mass spectrometry (MS). DAI-GC/MS gives excellent agreement with conventional purgeand-trap methods for MTBE over a wide range of environmentally relevant concentrations. The new method can also give simultaneous identification of polar compounds that might occur as degradation products of gasoline oxygenates, such as TBA, TBF, TAA, methyl acetate, and acetone. When the method was applied to effluent from a column microcosm prepared with core material from an urban site in New Jersey, conversion of MTBE to TBA was observed after a lag period of 35 days. However, to date, analyses of water samples from six field sites using the DAI-GC/MS method have not produced evidence for the expected products of in situ degradation of MTBE.

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Section: Resultsmentioning

confidence: 99%

Method for Determination of Methyltert-Butyl Ether and Its Degradation Products in Water

Church

Isabelle

Pankow

et al. 1997

Environ. Sci. Technol.

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Gas Chromatography by Direct Aqueous Injection in Environmental Analysis

Biziuk

2000

Encyclopedia of Analytical Chemistry

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Sample pretreatment, the initial stages of an analytical procedure, becomes the essential stage in environmental analysis. The only method of determination of organic compounds in water which avoids the isolation and preconcentration step uses direct injection of an aqueous sample on to a gas chromatographic column. Direct aqueous injection (DAI) is the simplest method for the determination of organic water pollutants. This method is also very fast and easy to automate. The method avoids the problems associated with using solvents (toxic and expensive) and incomplete recovery of the analytes during their isolation from the aqueous phase, the effect of potential contaminants when using solvent or solid‐phase extraction (SPE), and losses of the analytes during the enrichment step. The idea of DAI on to a chromatographic column is very old and for liquid chromatography and ion chromatography was widely applied from the beginning of these techniques. In the beginning of the application of this technique in gas chromatography (GC), packed columns were used. The real issue for the development of GC and the application of DAI is connected with introducing to practical use a capillary column with a polar or non‐polar stationary thin liquid film or thin layer. The next, very important step was to introduce a direct injection on‐column, which eliminates a lot of problems connected with injection in the split or splitless mode. The determination of haloforms in water using DAI on to a capillary column and electron capture detection (ECD) was the most spectacular application of this method. The DAI/GC/ECD method was used for determination of haloorganic compounds in the different aqueous samples (tap, surface, swimming pool, and seawaters, beers, juices, soft drinks, and physiological liquids). This method was also used for the determination of semivolatile and nonvolatile haloorganic and other organic compounds in the different aqueous samples.

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Trihalomethanes in Water, Analysis of

Lépine

Gilbert

2000

Encyclopedia of Analytical Chemistry

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Trihalomethanes (THMs) are considered to be the major by‐products found in water after the chlorination process. They mainly consist of chloroform (CHCl 3 ), bromodichloromethane (CHBrCl 2 ), dibromochloromethane (CHBr 2 Cl) and bromoform (CHBr 3 ). Their content in drinking water is regulated and the maximum contaminant level (MCL) of 100 µg L −1 established in 1979 by the United States Environmental Protection Agency (USEPA) for total THMs, based on a running annual average, still prevails and has been adopted in many other countries. In this article, we describe the four major analytical techniques routinely used for THM analysis. All of these analytical techniques use gas chromatography (GC) with a halogen‐specific detector such as the electron capture detector (ECD), electrolyte conductivity detector (ELCD) or mass spectrometry (MS). With high‐efficiency capillary columns now commonly available and the high sensitivity of the ECD, all these techniques have detection limits (DLs) at or below 0.1 µg L −1 for each of the four THMs, which is more than adequate for drinking water or beverage applications. The four analytical approaches differ by the way the THMs are introduced into the chromatographic column. Direct aqueous injection (DAI), where the sample is directly injected into the GC column, is fast and simple. It does not require any other piece of equipment than the gas chromatograph itself. However, since everything in the sample is injected in the column, it is limited to relatively clean matrices. It is generally used as a screening technique when a limited number of samples are analyzed. The second method uses liquid–liquid extraction (LLE) of the THMs with an organic solvent, usually pentane, which is then injected into the GC column. The extraction step offers the possibility of concentrating the THMs from a large‐volume sample and isolates them from inorganic salts. However, LLE is by far the most time‐consuming procedure and is not well suited for routine analysis of a large number of samples. The last two methods take advantage of the high volatility of the THMs to isolate and concentrate them in the gas phase. In the headspace (HS) technique, the aqueous sample is heated in a sealed vial and an equilibrium is reached between the THMs present in the water and the HS above, from which an aliquot is injected into the GC column. It is simple to use and easily automated. The sensitivity is limited by the partition coefficient of each species between the liquid and gas phases and the size of the gas aliquot injected into the GC column. The DL has been decreased to 1 ng L −1 by use of a long transfer time to the gas chromatograph and cryogenic trapping in the very first portion of the GC column. Finally, in the purge‐and‐trap (PT) technique, the THMs are purged out of the sample by an inert gas and concentrated on a solid sorbent, thermally desorbed and injected into the GC column. With a purge efficiency close to 100% for these volatile compounds, all the molecules present in a relatively large water sample (typically 5–25 mL) are injected into the GC column. It is the most sensitive of the four analytical methods and a DL below the 1 ng L −1 level has been achieved with cryogenic focusing at the column head.

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Trace analysis of halocarbons in water; Direct aqueous injection with electron capture detection

Cited by 53 publications

References 10 publications

Method for Determination of Methyltert-Butyl Ether and Its Degradation Products in Water

Method for Determination of Methyltert-Butyl Ether and Its Degradation Products in Water

Gas Chromatography by Direct Aqueous Injection in Environmental Analysis

Trihalomethanes in Water, Analysis of

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