Laboratory method for analysis of small concentrations of methyl tert-butyl rther and other ether gasoline oxygenates in water

Rose, Donna L.; Connor, Brooke F.; Abney, Sonja R.; Raese, Jon W.

doi:10.3133/fs08698

Cited by 9 publications

(10 citation statements)

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“…This matrix interference can be reduced by sample dilution but results in increased method detection limits (MDLs) for MTBE and TBA ( , ). Methods using GC−MS detection are more reliable for MTBE analysis in hydrocarbon mixtures ( , ) and are now recommended by the U.S. EPA () and U.K. Environment Agency ().…”

Section: Introductionmentioning

confidence: 99%

Improved Analysis of MTBE, TAME, and TBA in Petroleum Fuel-Contaminated Groundwater by SPME Using Deuterated Internal Standards with GC−MS

Dewsbury

Thornton

Lerner

2003

Environ. Sci. Technol.

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An improved method is described for the routine analysis of methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), and tert-butyl alcohol (TBA) in petroleum fuelcontaminated groundwater samples using solid-phase microextraction (SPME) and deuterated internal standards combined with gas chromatography mass spectrometry (GC-MS). Factors affecting method performance (SPME fiber selection, headspace or liquid extraction, extraction time, calibration conditions, salt addition, method sensitivity, and matrix effects) are evaluated using groundwater samples from a chalk aquifer contaminated with petroleum fuel containing MTBE, TAME, and TBA. The detection sensitivity and analytical efficiency of the method was optimized for these compounds using a PDMS-Carboxen fiber, sample NaCl content of 25% (w/v), and extraction time of 30 min. Internal calibration standards (deuterated MTBE and TBA) are necessary to control extraction errors during analysis. SPME extraction efficiency and detection sensitivity for the oxygenates and TBA decreased as the background matrix concentration of benzene, toluene, ethylbenzene, and xylenes (BTEX) increased up to 300 mg/L total BTEX. However, reliable measurement of MTBE, TAME, and TBA was possible in this BTEX matrix using deuterated internal standards. The precision, accuracy, and reliability of the method were verified by analysis of certified standards. Analytical accuracy, determined from replicate (n ) 10) analysis of spiked laboratory standards and groundwater samples, was 97%, with a precision of 1.6-2.9% for MTBE, 3.1-5.8% for TAME, and 1.6-1.7% for TBA. Method detection limits under the conditions described are 2 µg/L for TBA (by liquid sampling) and 1 µg/L for MTBE and TAME (by headspace sampling). This sensitivity can be increased for MTBE by further refinement of the method.

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Section: Introductionmentioning

confidence: 99%

Improved Analysis of MTBE, TAME, and TBA in Petroleum Fuel-Contaminated Groundwater by SPME Using Deuterated Internal Standards with GC−MS

Dewsbury

Thornton

Lerner

2003

Environ. Sci. Technol.

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“…At environmentally relevant pH values, the stability of MTBE is evident from standard solutions and controls used in numerous degradation studies carried out in our laboratory (unpublished data) and elsewhere [41–44]. Evidence for the stability of MTBE with respect to acid‐catalyzed hydrolysis can be found in control studies of analyte stability in samples preserved by acidification to pH 2 [45,46].…”

Section: Resultsmentioning

confidence: 99%

Hydrolysis of tert‐butyl formate: Kinetics, products, and implications for the environmental impact of methyl tert‐butyl ether

Church

Pankow

Tratnyek

1999

Enviro Toxic and Chemistry

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Asessing the environmental fate of methyl tert‐butyl ether (MTBE) has become a subject of renewed interest because of the large quantities of this compound that are being used as an oxygenated additive in gasoline. Various studies on the fate of MTBE have shown that it can be degraded to tert‐butyl formate (TBF), particularly in the atmosphere. Although it is generally recognized that TBF is subject to hydrolysis, the kinetics and products of this reaction under environmentally relevant conditions have not been described previously. In this study, we determined the kinetics of TBF hydrolysis as a function of pH and temperature. Over the pH range of 5 to 7, the neutral hydrolysis pathway predominates, with kN = (1.0 ± 0.2) × 10−6/s. Outside this range, strong pH effects were observed because of acidic and basic hydrolyses, from which we determined that kA = (2.7 ± 0.5) × 10−3/(M·s) and kB = 1.7 ± 0.3/(M·s). Buffered and unbuffered systems gave the same hydrolysis rates for a given pH, indicating that buffer catalysis was not significant under the conditions tested. The activation energies corresponding to kN, kA, and kB were determined to be 78 ± 5, 59 ± 4, and 88 ±11 kJ/mol, respectively. In all experiments, tert‐butyl alcohol was found at concentrations corresponding to stoichiometric formation from TBF. Based on our kinetics data, the expected half‐life for hydrolysis of TBF at pH = 2 and 4°C (as per some standard preservation protocols for water sampling) is 6 h. At neutral pH and 22°C, the estimated half‐life is 5 d, and at pH = 11 and 22°C, the value is only 8 min.

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“…At environmentally relevant pH values, the stability of MTBE is evident from standard solutions and controls used in numerous degradation studies carried out in our laboratory (unpublished data) and elsewhere [41][42][43][44]. Evidence for the stability of MTBE with respect to acid-catalyzed hydrolysis can be found in control studies of analyte stability in samples preserved by acidification to pH 2 [45,46].…”

Section: Hydrolysis Kineticsmentioning

confidence: 86%

HYDROLYSIS OF tert-BUTYL FORMATE: KINETICS, PRODUCTS, AND IMPLICATIONS FOR THE ENVIRONMENTAL IMPACT OF METHYL tert-BUTYL ETHER

Church¹,

Pankow²,

Tratnyek³

1999

Environ Toxicol Chem

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Abstract-Assessing the environmental fate of methyl tert-butyl ether (MTBE) has become a subject of renewed interest because of the large quantities of this compound that are being used as an oxygenated additive in gasoline. Various studies on the fate of MTBE have shown that it can be degraded to tert-butyl formate (TBF), particularly in the atmosphere. Although it is generally recognized that TBF is subject to hydrolysis, the kinetics and products of this reaction under environmentally relevant conditions have not been described previously. In this study, we determined the kinetics of TBF hydrolysis as a function of pH and temperature. Over the pH range of 5 to 7, the neutral hydrolysis pathway predominates, with k N ϭ (1.0 Ϯ 0.2) ϫ 10 Ϫ6 /s. Outside this range, strong pH effects were observed because of acidic and basic hydrolyses, from which we determined that k A ϭ (2.7 Ϯ 0.5) ϫ 10 Ϫ3 / (M·s) and k B ϭ 1.7 Ϯ 0.3/(M·s). Buffered and unbuffered systems gave the same hydrolysis rates for a given pH, indicating that buffer catalysis was not significant under the conditions tested. The activation energies corresponding to k N , k A , and k B were determined to be 78 Ϯ 5, 59 Ϯ 4, and 88 Ϯ 11 kJ/mol, respectively. In all experiments, tert-butyl alcohol was found at concentrations corresponding to stoichiometric formation from TBF. Based on our kinetics data, the expected half-life for hydrolysis of TBF at pH ϭ 2 and 4ЊC (as per some standard preservation protocols for water sampling) is 6 h. At neutral pH and 22ЊC, the estimated half-life is 5 d, and at pH ϭ 11 and 22ЊC, the value is only 8 min.

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Laboratory method for analysis of small concentrations of methyl tert-butyl rther and other ether gasoline oxygenates in water

Cited by 9 publications

References 0 publications

Improved Analysis of MTBE, TAME, and TBA in Petroleum Fuel-Contaminated Groundwater by SPME Using Deuterated Internal Standards with GC−MS

Improved Analysis of MTBE, TAME, and TBA in Petroleum Fuel-Contaminated Groundwater by SPME Using Deuterated Internal Standards with GC−MS

Hydrolysis of tert‐butyl formate: Kinetics, products, and implications for the environmental impact of methyl tert‐butyl ether

HYDROLYSIS OF tert-BUTYL FORMATE: KINETICS, PRODUCTS, AND IMPLICATIONS FOR THE ENVIRONMENTAL IMPACT OF METHYL tert-BUTYL ETHER

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