Continuous-Flow Stable Sulfur Isotope Analysis of Organic and Inorganic Compounds by EA-MC-ICPMS.

Elemental analysis (EA) coupled to isotope ratio mass spectrometry (IRMS) is a well-established method to derive stable isotope ratios of sulfur (S/S). Conversion of sulfur to SO by EA and measurement of SO isotopologues by IRMS represents the simplest and most versatile method to accomplish isotope measurement of sulfur even in bulk samples. Yet, interferences by oxygen isotopes in SO often impair the precision and trueness of measured results.

Simultaneous Compound-Specific Analysis of δS and δS in Organic Compounds by GC-MC-ICPMS Using Medium- and Low-Mass-Resolution Modes.

Compound-specific isotope analysis of sulfur (δS-CSIA) in organic compounds was established in the last decade employing gas chromatography connected to multiple-collector inductively coupled plasma mass spectrometry (GC-MC-ICPMS). However, δS-CSIA has not yet been reported so far. In this study, we present a method for the simultaneous determination of δS and δS in organic compounds by GC-MC-ICPMS applying medium- and also low-mass-resolution modes.

Isotope fractionation (H/H, C/C, Cl/Cl) in trichloromethane and trichloroethene caused by partitioning between gas phase and water.

Transfer of organic compounds between aqueous and gaseous phases may change the isotopic composition which complicates the isotopic characterization of sources and transformation mechanisms in environmental samples. Studies investigating kinetic phase transfer of compounds dissolved in water (volatilization) are scarce, even though it presents an environmentally very relevant phase transfer scenario. In the current study, the occurrence of kinetic isotope fractionation (H/H, C/C, Cl/Cl) was investigated for two volatile organic compounds (trichloroethene, TCE and trichloromethane, TCM) during volatilization from water and gas-phase dissolution in water.

Chlorine Isotope Fractionation of the Major Chloromethane Degradation Processes in the Environment.

Chloromethane (CHCl) is an important source of chlorine in the stratosphere, but detailed knowledge of the magnitude of its sources and sinks is missing. Here, we measured the stable chlorine isotope fractionation (ε) associated with the major abiotic and biotic CHCl sinks in the environment, namely, CHCl degradation by hydroxyl (OH) and chlorine (Cl) radicals in the troposphere and by reference bacteria CM4 and MB2 from terrestrial and marine environments, respectively. No chlorine isotope fractionation was detected for reaction of CHCl with OH and Cl radicals, whereas a large chlorine isotope fractionation (ε) of -10.

Transformation of Chlorofluorocarbons Investigated via Stable Carbon Compound-Specific Isotope Analysis.

Compound-specific isotope analysis (CSIA) is a valuable tool in contaminant remediation studies. Chlorofluorocarbons (CFCs) are ozone-depleting substances previously thought to be persistent in groundwater under most geochemical conditions but more recently have been found to (bio)transform in some laboratory experiments. To date, limited applications of CSIA to CFCs have been undertaken.

Isotopic Characterization (H, C, Cl, Br) of Abiotic Degradation of Methyl Bromide and Methyl Chloride in Water and Implications for Future Studies.

Methyl bromide (CHBr) and methyl chloride (CHCl) significantly contribute to stratospheric ozone depletion. The atmospheric budgets of both compounds are unbalanced with known degradation processes outweighing known emissions. Stable isotope analysis may be capable to identify and quantify emissions and to achieve a balanced budget.

Compound Specific Stable Chlorine Isotopic Analysis of Volatile Aliphatic Compounds Using Gas Chromatography Hyphenated with Multiple Collector Inductively Coupled Plasma Mass Spectrometry.

Stable chlorine isotope analysis is increasingly used to characterize sources, transformation pathways, and sinks of organic aliphatic compounds, many of them being priority pollutants in groundwater and the atmosphere. A wider use of chlorine isotopes in environmental studies is still inhibited by limitations of the different analytical techniques such as high sample needs, offline preparation, confinement to few compounds and mediocre precision, respectively. Here we present a method for the δCl determination in volatile aliphatic compounds using gas chromatography coupled with multiple-collector inductively coupled plasma mass spectrometry (GC-MC-ICPMS), which overcomes these limitations.

Vapor Pressure Isotope Effects in Halogenated Organic Compounds and Alcohols Dissolved in Water.

Volatilization causes changes in the isotopic composition of organic compounds as a result of different vapor pressures of molecules containing heavy and light isotopes. Both normal and inverse vapor pressure isotope effects (VPIE) have been observed, depending on molecular interactions in the liquid phase and the investigated element. Previous studies have focused mostly on pure compound volatilization or on compounds dissolved in organic liquids.

Methyl chloride and methyl bromide emissions from baking: an unrecognized anthropogenic source.

Methyl chloride and methyl bromide (CH3Cl and CH3Br) are the largest natural sources of chlorine and bromine, respectively, to the stratosphere, where they contribute to ozone depletion. We report the anthropogenic production of CH3Cl and CH3Br during breadbaking, and suggest this production is an abiotic process involving the methyl ester functional groups in pectin and lignin structural polymers of plant cells. Wide variations in baking styles allow only rough estimates of this flux of methyl halides on a global basis.

Compound-Specific Stable Carbon Isotope Analysis of Chlorofluorocarbons in Groundwater.

Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), controlled substances due to their role in stratospheric ozone loss, also occur as dissolved contaminants in groundwaters. Stable carbon isotopic signatures may provide valuable new information on the fate of these compounds as has been seen for other priority hydrocarbon contaminants, but to date no method for extraction and isotopic analysis of dissolved CFCs from groundwaters has been developed. Here we describe a cryogenic purge and trap system coupled to continuous flow compound-specific stable carbon isotope analysis mass spectrometry for concentrations as low as 35 μg/L.

Compound-specific bromine isotope analysis of methyl bromide using gas chromatography hyphenated with inductively coupled plasma multiple-collector mass spectrometry.

Methyl bromide is the most important natural bromine contributor to stratospheric ozone depletion, yet there are still large uncertainties regarding quantification of its sources and sinks. The stable bromine isotope composition of CH(3)Br is potentially a powerful tool to apportion its sources and to study both its transport and its reactive fate. A novel compound-specific method to measure (81)Br/(79)Br isotope ratios in CH(3)Br using gas chromatography hyphenated with inductively coupled plasma multiple-collector mass spectrometry (GC/MCICPMS) was developed.

Estimating groundwater mixing and origin in an overexploited aquifer in Guanajuato, Mexico, using stable isotopes (strontium-87, carbon-13, deuterium and oxygen-18).

Stable Isotopes (strontium-87, deuterium and oxygen-18, carbon-13) have been used to reveal different sources of groundwater and mixing processes in the aquifer of the Silao-Romita Valley in the state of Guanajuato, Mexico. Calcite dissolution appeared to be the main process of strontium release leading to relatively equal (87)Sr/(86)Sr ratios of 0.7042-0.