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GC Analysis (gc + analysis)
Selected AbstractsComparison of DNA-Reactive Metabolites from Nitrosamine and Styrene Using Voltammetric DNA/Microsomes SensorsELECTROANALYSIS, Issue 9 2009Sadagopan Krishnan Abstract Voltammetric sensors made with films of polyions, double-stranded DNA and liver microsomes adsorbed layer-by-layer onto pyrolytic graphite electrodes were evaluated for reactive metabolite screening. This approach features simple, inexpensive screening without enzyme purification for applications in drug or environmental chemical development. Cytochrome P450 enzymes (CYPs) in the liver microsomes were activated by an NADPH regenerating system or by electrolysis to metabolize model carcinogenic compounds nitrosamine and styrene. Reactive metabolites formed in the films were trapped as adducts with nucleobases on DNA. The DNA damage was detected by square-wave voltammetry (SWV) using Ru(bpy) as a DNA-oxidation catalyst. These sensors showed a larger rate of increase in signal vs. reaction time for a highly toxic nitrosamine than for the moderately toxic styrene due to more rapid reactive metabolite-DNA adduct formation. Results were consistent with reported in vivo TD50 data for the formation of liver tumors in rats. Analogous polyion/ liver microsome films prepared on 500,nm silica nanoparticles (nanoreactors) and reacted with nitrosamine or styrene, provided LC-MS or GC analyses of metabolite formation rates that correlated well with sensor response. [source] Evaluation of use of a very short polar microbore column segment in high-speed gas chromatography analysisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2008Peter Quinto Tranchida Abstract Very fast GC analyses are commonly carried out by using 10 m×0.1 mm id capillaries. In order to achieve rapid elution times (1,3 min), the latter are operated under suboptimum conditions. The present research is focused on the evaluation of use of a 0.1 mm id polar column segment (2 m), operated under near-to-optimum conditions, in very fast GC analysis. The results attained are compared with those derived from using a 10 m microbore column in very fast GC experiments. Prior to method development, the effects of gas velocity, temperature program rate, and sample amounts on analytical performance were evaluated. Following these preliminary applications, a complex lipidic sample, cod liver oil, was subjected to rapid separation (,2.1 min) on the 10 m capillary through the application of a 50°C/min temperature rate and a 130 cm/s gas velocity. The same matrix was analyzed on the 2 m capillary using the same temperature program rate and range, but with a close-to-ideal linear velocity. The results observed were of interest, as the separation was achieved in less time (1.45 min) with improved peak resolution. Finally, both methods were validated in terms of retention time and peak area repeatability, LOQ, and linearity. [source] Biosynthesis of the Myxobacterial Antibiotic Corallopyronin ACHEMBIOCHEM, Issue 9 2010Özlem Erol Abstract Corallopyronin A is a myxobacterial compound with potent antibacterial activity. Feeding experiments with labelled precursors resulted in the deduction of all biosynthetic building blocks for corallopyronin A and revealed an unusual feature of this metabolite: its biosynthesis from two chains, one solely PKS-derived and the other NRPS/PKS-derived. The starter molecule is believed to be carbonic acid or its monomethyl ester. The putative corallopyronin A biosynthetic gene cluster is a trans-AT-type mixed PKS/NRPS gene cluster, containing a ,-branching cassette. Striking features of this gene cluster are a NRPS-like adenylation domain that is part of a PKS-type module and is believed to be responsible for glycine incorporation, as well as split modules with individual domains occurring on different genes. It is suggested that CorB is a trans-acting ketosynthase and it is proposed that it catalyses the Claisen condensation responsible for the interconnection of the two chains. Additionally, the stereochemistry of corallopyronin A was deduced by a combination of a modified Mosher's method and ozonolysis with subsequent chiral GC analyses. [source] Micro-reactor for transesterification of plant seed oilsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2009Phattaraporn Kaewkool Abstract The fatty acid compositions of vegetable or other plant seed oils are generally determined by gas chromatography (GC). Methyl esters (the most volatile derivatives) are the preferred derivatives for GC analysis. Esters of higher alcohols are good for the separation of volatile and positional isomers. All the esters of the C1,C8 alcohols of vegetable oils were silmilarly prepared by passing the reaction mixture containing the desired alcohol, oil and tetrahydrofuran through the micro-reactor (a 3-mL dispossible syringe packed with 0.5,g of NaOH powder). The reaction products were acidified with acetic acid and the mixture was analyzed by high-performance size exclusion chromatography and GC. Transesterification was quantitative for primary alcohols, but an appreciable amount of free fatty acids was formed for secondary alcohols. Coriander seed oil was quantitatively esterified with 2-ethyl 1-hexanol with the micro-reactor in less than 1,min. Oleic and petroselinic acid 2-ethyl 1-hexyl esters are baseline separated on an Rtx-2330 capillary column (30,m×0.25,mm, 0.25,µm film thickness). [source] Signi,cance of changed climatic factors on essential oil composition of Echinacea purpurea under subtropical conditions,FLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2004R. K. Thappa Abstract Variation pattern in the composition of essential oil, hydrodistilled from the over-matured ,ower heads of Echinacea purpurea (L.) Moench under subtropical climate was characterized by GC,MS and GC analysis. The plants ,ower from June till December and climatic factors such as temperature and humidity were found to affect both the content and the composition of the essential oil. Copyright © 2004 John Wiley & Sons, Ltd. [source] Thermal decomposition of cyclic organic peroxides in pure solvents and binary solvent mixturesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2010Mariángeles Iglesias The thermal decomposition reaction of acetone cyclic triperoxide, acetone cyclic diperoxide, 4-heptanone cyclic diperoxide, and pinacolone cyclic diperoxide ca. 0.02 M was studied in pure solvents (acetone and 1-propanol) and in binary mixtures of acetone/1-propanol at 150°C. The kinetics of each system was explored by gas chromatography (GC) at different solvent compositions. The reactions showed a behavior accordingly with a pseudo-first-order kinetic law up to at least 90% peroxide decomposition. The main organic products derived from these thermolysis reactions were detected by GC analysis. Among them, the corresponding ketones, methane, ethane, and propane were the main identified products. The rates of decomposition of pinacolone diperoxide in the pure solvents were practically independent of the solvent characteristics, so it was of no interest to analyze its kinetic behavior in binary solvent mixtures. In acetone/1-propanol mixtures, the solvation effect on the cyclic peroxides derived from 4-heptanone and acetone molecules was slightly dominated by specific interactions between 1-propanol and a diradical-activated complex initially formed. This species was preferentially solvated by 1-propanol instead of acetone. Specific interactions between the O atoms from the peroxidic bond and the H from the OH in 1-propanol can be taken into account. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 347,353, 2010 [source] Ecophysiological attributes of a Lactobacillus sp. and a Pseudomonas sp. on sterile beef fillets in relation to storage temperature and film permeabilityJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2001E. Tsigarida Aims:,To determine the combined effect of packaging film and temperature on the rate and type of end-products caused by the growth of two main contrasting prevailing organisms in air and 100% CO2, Pseudomonas sp. and Lactobacillus sp., respectively. Methods and Results:,Pseudomonas sp. and Lactobacillus sp. were inoculated individually on sterile meat fillets. The samples were packed in air or 100% CO2, using a high and a low permeable film, and stored at 0 and 10°C. Pseudomonas sp. grew aerobically and in 100% CO2 using high permeable film at both storage temperatures, while film permeability significantly affected the growth of Lactobacillus sp. only at 10°C. Enzymatic kits and HPLC and GC analysis were used to determine the chemical changes of the samples throughout storage. Pseudomonas sp. presented a greater rate of consumption of glucose and lactate than Lactobacillus sp. in samples stored aerobically or with high permeable film. Propanol-1 and two unidentified organic acids were present only in samples inoculated with Pseudomonas sp., while acetaldehyde, ethanol, diacetyl and acetoin were detected in samples inoculated with Lactobacillus sp. Conclusions:,Since different microbial species and introduction of new packaging methods affect spoilage reactions of meat either qualitatively or quantitatively, a combination of several chemical indicators should be thoroughly investigated. Significance and Impact of the Study:,The present study provides information on how and when such potential indicators can be exploited for the benefit of the industry and consumer. [source] Evaluation of use of a very short polar microbore column segment in high-speed gas chromatography analysisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2008Peter Quinto Tranchida Abstract Very fast GC analyses are commonly carried out by using 10 m×0.1 mm id capillaries. In order to achieve rapid elution times (1,3 min), the latter are operated under suboptimum conditions. The present research is focused on the evaluation of use of a 0.1 mm id polar column segment (2 m), operated under near-to-optimum conditions, in very fast GC analysis. The results attained are compared with those derived from using a 10 m microbore column in very fast GC experiments. Prior to method development, the effects of gas velocity, temperature program rate, and sample amounts on analytical performance were evaluated. Following these preliminary applications, a complex lipidic sample, cod liver oil, was subjected to rapid separation (,2.1 min) on the 10 m capillary through the application of a 50°C/min temperature rate and a 130 cm/s gas velocity. The same matrix was analyzed on the 2 m capillary using the same temperature program rate and range, but with a close-to-ideal linear velocity. The results observed were of interest, as the separation was achieved in less time (1.45 min) with improved peak resolution. Finally, both methods were validated in terms of retention time and peak area repeatability, LOQ, and linearity. [source] Rapid analysis of food products by means of high speed gas chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2007Paola Donato Abstract Since the invention of GC, there has been an ever increasing interest within the chromatographic community for faster GC methods. This is obviously related to the fact that the number of samples subjected to GC analysis has risen greatly. Nowadays, in routine analytical applications, sample throughput is often the most important aspect considered when choosing an analytical method. Gas chromatographic instrumentation, especially in the last decade, has been subjected to continuous and considerable improvement. High-speed injection systems, electronic gas pressure control, rapid oven heating/cooling and fast detection are currently available in a variety of commercial gas chromatographs. The main consequence of this favourable aspect is that high-speed GC is being increasingly employed for routine analysis in different fields. Furthermore, the employment of dedicated software makes the passage from a conventional to a fast GC method a rather simple step. The present review provides an overview of the employment of fast GC techniques for the analysis of food constituents and contaminants. A brief historical and theoretical background is also provided for the approaches described. [source] Analysis of isomeric tropane alkaloids from Schizanthus grahamii by very fast gas chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2006Stefan Bieri Abstract This study presents a very fast GC analysis applied for the baseline separation of isomeric tropane alkaloids extracted from the stem-bark of Schizanthus grahamii (Solanaceae). The work provided a challenging application where isothermal analysis in conjunction with very short narrow bore columns (3 m×100 ,m ID and 1.5 m×50 ,m ID) was particularly suited for the speeding up. Experimental parameters were used in the optimisation steps, including selection of stationary phase, temperature, internal column diameter and optimal practicable gas velocity. Some considerations about sample injection in fast isothermal analysis are also briefly presented. Finally, the investigated approach allowed a very fast baseline separation of four positional and configurational isomers in less than 9 s. [source] Fast GC analysis with a 50 ,m ID column: theory, practical aspects, and application to a highly complex sampleJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2004Luigi Mondello Abstract This research focuses on the minimization of GC analysis times through the use of a 5 m×0.05 mm ID×0.05 ,m (film thickness) column. Experimental minimum plate height (Hmin) and optimum linear velocity values were derived from standard compound applications, under various analytical conditions, and then related to classical chromatographic theory. Deviations from the latter are measured and discussed. Practical aspects linked to the use of such capillaries, such as column sample capacity and detector acquisition rates, are also considered. Furthermore, a fast, and what can be considered a very fast method, were applied to the separation of a fuel sample. Coefficients of variation of elution times and relative peak areas were calculated in the very fast application. All analytical results are compared with those obtained by conventional 0.25 mm ID column applications. [source] GC analysis of extractive compounds in beech woodJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2003Janja Zule Abstract Various highly hydrophobic beech wood lipids were characterized and their quantities measured in hexane extracts by GC, using short and long capillary columns. More polar compounds were also identified in acetone extracts. Triglycerides, steryl esters, sterols, unsaturated fatty acids, as well as various monosaccharide units were determined as possible pollutants of papermaking systems. [source] Age and space distributions of monoterpenes in fresh needles of Picea abies (L) Karst. determined by gas chromatography-mass spectrometryPHYTOCHEMICAL ANALYSIS, Issue 4 2001V. Holubová Abstract Monoterpenes (,- and ,-pinene, ,-3-carene, camphene, ,-phellandrene and limonene) were determined by Gas Chromatography-Mass Spectrometry in fresh needles of Picea abies (L) Karst. situated in three ecologically different regions of Moravia. Through the use of cryogenic grinding for critical sample homogenisation, solvent extraction with cold n -hexane, followed by GC analysis with mass detection, very low quantities of sample (0.1,0.3,g needles) could be processed, thus permitting a comparison of amounts of monoterpenes in needles of different ages and a determination of changes in concentrations of monoterpenes in needles at different locations on the tree. The amount of ,-phellandrene decreased with the age of the needles, and the content of ,-3-carene was higher in apical branches compared to lateral ones. Copyright © 2001 John Wiley & Sons, Ltd. [source] False-positive liquid chromatography/tandem mass spectrometric confirmation of sebuthylazine residues using the identification points system according to EU directive 2002/657/EC due to a biogenic insecticide in tarragonRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Andreas Schürmann In pesticide residue analysis using liquid chromatography/tandem mass spectrometry (LC/MS/MS) the confirmation of a sebuthylazine finding in a tarragon (Artemisia dranunculus) sample was demonstrated to be false positive. A coeluting interfering matrix compound produced product ions in MS/MS analysis, perfectly corresponding to the multiple reaction monitoring (MRM) of two sebuthylazine transitions. Using the EU directive 2002/657/EC which regulates the confirmation of suspected positive findings would have resulted in a false-positive finding. A third LC/MS/MS transition with a deviant ion ratio and a gas chromatography (GC)/MS/MS analysis revealed the false-positive results. With optimized high resolving ultra-performance liquid chromatography (UPLC) conditions it was possible to separate spiked sebuthylazine from the interfering matrix compound. Using its exact mass and isotope ratios from LC/time-of-flight (TOF) MS measurements, the compound was identified as nepellitorine, a , not surprising , endogenous alkamide in tarragon (Arthemisia dranunculus). False-positive results, especially in heavy matrix samples such as herbs, can be dealt with by further confirmatory analysis, e.g. a third transition, GC analysis if possible or more advantageous by an orthogonal criterion like exact mass. Copyright © 2009 John Wiley & Sons, Ltd. [source] Maximized PUFA measurements improve insight in changes in fatty acid composition in response to temperatureARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2009Coby van Dooremalen Abstract A general mechanism underlying the response of ectotherms to environmental changes often involves changes in fatty acid composition. Theory predicts that a decrease in temperature causes an increase in unsaturation of fatty acids, with an important role for long-chain poly-unsaturated fatty acids (PUFAs). However, PUFAs are particularly unstable and susceptible to peroxidation, hence subtle differences in fatty acid composition can be challenging to detect. We determined the fatty acid composition in springtail (Collembola) in response to two temperatures (5°C and 25°C). First, we tested different sample preparation methods to maximize PUFAs. Treatments consisted of different solvents for primary lipid extraction, mixing with antioxidant, flushing with inert gas, and using different temperature exposures during saponification. Especially slow saponification at low temperature (90,min at 70°C) in combination with replacement of headspace air with nitrogen during saponification and methylation maximized PUFAs for GC analysis. Applying these methods to measure thermal responses in fatty acid composition, the data showed that the (maximized) proportion of C20 PUFAs increased at low acclimation temperature. However, C18 PUFAs increased at high acclimation temperature, which is contrary to expectations. Our study illustrates that PUFA levels in lipids may often be underestimated and this may hamper a correct interpretation of differential responses of fatty acid composition. © 2009 Wiley Periodicals, Inc. [source] Optimizing acidic methanolysis of poly(3-hydroxyalkanoates) in gas chromatography analysisASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009Chi-Wei Lo Abstract This work was undertaken to develop an improved gas chromatography (GC) analysis of poly (3-hydroxyalkanoate) (PHA) quantification method based on acidic methanolysis. This is achieved by investigating the kinetics of acidic hydrolysis of PHAs with sulfuric acid in the chloroform/aqueous solution to identify suitable hydrolytic pretreatment conditions for quantitative analysis of PHAs. The target parameters included sulfuric acid concentration, salt (NaCl) addition, kind of PHAs (commercial products of poly-3-hydroxybutyrate (PHB), poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV-8%) and poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) (PHBHHx-3.8% and-10.5%), as well as the type of PHA-producing microorganisms (Cupriavidus taiwanensis 184 and Burkholderia sp. PTU9). These results show that esters would preferentially accumulate in the organic phase when NaCl was added in the two-phase system, thereby enhancing the accuracy of GC analysis. Decomposition efficiency of different types of PHAs was found to be dependent on sulfuric acid concentration, such as 1% H2SO4 was favorable for PHB decomposition, while 5 and 7% H2SO4 should be used to decompose PHBV and PHBHHx. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Purification of bioethanol effluent in an UASB reactor system with simultaneous biogas formationBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2003M. Torry-Smith In this study, the prospect of using an Upflow Anaerobic Sludge Blanket (UASB) reactor for detoxification of process water derived from bioethanol production has been investigated. The bioethanol effluent (BEE) originated from wet oxidized wheat straw fermented by Saccharomyces cerevisiae and Thermoanaerobacter mathranii A3M4 to produce ethanol from glucose and xylose, respectively. In batch experiments the methane potential of BEE was determined to 529 mL-CH4/g-VS. In batch degradation experiments it was shown that the presence of BEE had a positive influence on the removal of the inhibitors 2-furoic acid, 4-hydroxyacetophenone, and acetovanillone as compared to conversion of the inhibitors as sole substrate in synthetic media. Furthermore, experiments were carried out treating BEE in a laboratory-scale UASB reactor. The results showed a Chemical Oxygen Demand (COD) removal of 80% (w/w) at an organic loading rate of 29 g-COD/(L · d). GC analysis of the lignocellulosic related potentially inhibitory compounds 2-furoic acid, vanillic acid, homovanillic acid, acetovanillone, syringic acid, acetosyringone, syringol, 4-hydroxybenzoic acid, and 4-hydroxybenzaldehyde showed that all of these compounds were removed from the BEE in the reactor. Implementation of a UASB purification step was found to be a promising approach to detoxify process water from bioethanol production allowing for recirculation of the process water and reduced production costs. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 7,12, 2003. [source] Mechanism of Laccase,TEMPO-Catalyzed Oxidation of Benzyl AlcoholCHEMCATCHEM, Issue 7 2010Sander Abstract The oxidation of benzyl alcohol by air, catalyzed by the organocatalyst TEMPO and the enzyme laccase has been investigated. To establish the kinetically significant pathways and corresponding kinetic parameters, a series of experiments is conducted with synthesized stable oxidized and reduced forms of the organocatalyst, the oxoammonium cation, and hydroxylamine. The time course of TEMPO and its oxidized and reduced derivatives is monitored off line by a combination of GC analysis, UV/Vis spectroscopy, EPR spectroscopy, and FTIR spectroscopy. TEMPO is found to be regenerated through noncatalyzed comproportionation of the oxoammonium cation with hydroxylamine. A kinetic model is presented based on the experimentally determined kinetically significant pathways. The time dependences of the concentrations of the three redox states of TEMPO and benzyl alcohol are adequately described by the model. The results provide new leads for the development of a practical process for a combined laccase,TEMPO-catalyzed selective oxidation of alcohols. [source] Application of solid phase microextraction for the determination of soil fumigants in water and soil samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2005Sonia Fuster Abstract The potential of solid phase microextraction (SPME) for the determination of the soil fumigants 1,3-dichloropropene (1,3-DCP) and methyl isothiocyanate (MITC) in environmental samples such as soil and water samples has been investigated. Direct immersion SPME followed by GC/ECD/NPD analysis allowed the rapid determination of the two fumigants in water samples, with very little sample manipulation, giving an LOD of 0.5 ,g L,1. Precision, calculated as relative standard deviation (RSD) for six replicates at three concentration levels, was found to be lower than 20% at the concentration levels tested. For the analysis of soil samples, headspace (HS)-SPME combined with GC/ECD/NPD analysis has been applied. Quantification using matrix-matched calibration curves allowed determination of both analytes (MITC and 1-3-DCP) with a LOD of 0.1 ,g kg,1 (RSD <10%) for the two concentration levels assayed (0.02 and 0.2 mg kg,1). The HS-SPME procedure developed in this paper was applied to soil samples from experimental green house plots treated with metham-Na, a soil disinfestation agent that decomposes in soil to MITC. The absence of sample manipulation as well as the low solvent consumption in SPME methodology are among the main advantages of this analytical approach. [source] Metabolism of Deuterated erythro -Dihydroxy Fatty Acids in Saccharomyces cerevisiae: Enantioselective Formation and Characterization of HydroxylactonesHELVETICA CHIMICA ACTA, Issue 6 2008Leif-A. Abstract Epoxides of fatty acids are hydrolyzed by epoxide hydrolases (EHs) into dihydroxy fatty acids which are of particular interest in the mammalian leukotriene pathway. In the present report, the analysis of the configuration of dihydroxy fatty acids via their respective hydroxylactones is described. In addition, the biotransformation of (±)- erythro -7,8- and -3,4-dihydroxy fatty acids in the yeast Saccharomyces cerevisiae was characterized by GC/EI-MS analysis. Biotransformation of chemically synthesized (±)- erythro -7,8-dihydroxy(7,8- 2H2)tetradecanoic acid ((±)- erythro - 1) in the yeast S. cerevisiae resulted in the formation of 5,6-dihydroxy(5,6- 2H2)dodecanoic acid (6), which was lactonized into (5S,6R)-6-hydroxy(5,6- 2H2)dodecano-5-lactone ((5S,6R)- 4) with 86% ee and into erythro -5-hydroxy(5,6- 2H2)dodecano-6-lactone (erythro - 8). Additionally, the , -ketols 7-hydroxy-8-oxo(7- 2H1)tetradecanoic acid (9a) and 8-hydroxy-7-oxo(8- 2H1)tetradecanoic acid (9b) were detected as intermediates. Further metabolism of 6 led to 3,4-dihydroxy(3,4- 2H2)decanoic acid (2) which was lactonized into 3-hydroxy(3,4- 2H2)decano-4-lactone (5) with (3R,4S)- 5=88% ee. Chemical synthesis and incubation of (±)- erythro -3,4-dihydroxy(3,4- 2H2)decanoic acid ((±)- erythro - 2) in yeast led to (3S,4R)- 5 with 10% ee. No decano-4-lactone was formed from the precursors 1 or 2 by yeast. The enantiomers (3S,4R)- and (3R,4S)-3,4-dihydroxy(3- 2H1)nonanoic acid ((3S,4R)- and (3R,4S)- 3) were chemically synthesized and comparably degraded by yeast without formation of nonano-4-lactone. The major products of the transformation of (3S,4R)- and (3R,4S)- 3 were (3S,4R)- and (3R,4S)-3-hydroxy(3- 2H1)nonano-4-lactones ((3S,4R)- and (3R,4S)- 7), respectively. The enantiomers of the hydroxylactones 4, 5, and 7 were chemically synthesized and their GC-elution sequence on Lipodex®E chiral phase was determined. [source] Used Motor Oil as a Source of MTBE, TAME, and BTEX to Ground WaterGROUND WATER MONITORING & REMEDIATION, Issue 4 2002Ronald J. Baker Methyl tert-butyl ether (MTBE), the widely used gasoline oxygenate, has been identified as a common ground water contaminant, and BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) have long been associated with gasoline spills. Because not all instances of ground water contamination by MTBE and BTEX can be attributed to spills or leaking storage tanks, other potential sources need to be considered. In this study, used motor oil was investigated as a potential source of these contaminants. MTBE in oil was measured directly by methanol extraction and gas chromatography using a flame ionization detector (GC/FID). Water was equilibrated with oil samples and analyzed for MTBE, BTEX, and the oxygenate tert-amyl methyl ether (TAME) by purge- and-trap concentration followed by GC/FID analysis. Raoult's law was used to calculate oil-phase concentrations of MTBE, BTEX, and TAME from aqueous-phase concentrations. MTBE, TAME, and BTEX were not detected in any of five new motor oil samples, whereas these compounds were found at significant concentrations in all six samples of the used motor oil tested for MTBE and all four samples tested for TAME and BTEX. MTBE concentrations in used motor oil were on the order of 100 mg/L. TAME concentrations ranged from 2.2 to 87 mg/L. Concentrations of benzene were 29 to 66 mg/L, but those of other BTEX compounds were higher, typically 500 to 2000 mg/L. [source] | |||||||||||||