Sakaguchi-Söder, Kaori ; Pichlmaier, J. ; Ertl, S. (2017)
Simplified Method To Determine Chlorine and Bromine Isotope Ratios Of Chloride and Bromide In Water By GC-qMS.
Jahrestagung der Arbeitsgemeinschaft Stabile Isotope e.V.. Universität Hannover, Leibnizhaus (09.10.2017-11.10.2017)
Conference or Workshop Item, Bibliographie

Abstract

Compound-specific stable isotope analysis (CSIA) is a technique to determine stable isotope ratio of a certain element in an organic compound. The application of CSIA for chlorine (Cl-CSIA) or bromine (Br-CSIA) is highly relevant to study fate and transport of pollutants in the environment, since many of environmental pollutants are halogenated organic compounds. Yet, their application is limited due to mainly three difficulties: (1) the use of high-resolution mass spectrometer (IRMS), which is not readily available, (2) the requirement of an upstream, time-consuming chemical conversion of chlorine or chloride to methyl chloride (CH3Cl) for IRMS analysis and (3) an absence of standards that can be injected to gas chromatograph (GC). Available isotope standards for chlorine and bromine are in a form of chloride or bromide, not in a form of organic compounds. Here, we present a set of simple and innovative techniques for Cl- and Br-CSIA for chloride and bromide in the water phase. The techniques were developed through a collaboration between Hydroisotop GmbH (Schweitenkirchen) and TU Darmstadt. Hydroisotop GmbH has successfully developed a quick and innovative method to convert chloride in the water phase to isopropyl chloride (IPCl) and bromide to isopropyl bromide (IPBr). Briefly, a water sample containing chloride and/or bromide in a vial is to be evaporated to dryness at 120 C. Then, phosphoric acid and isopropanol are added to the vial. The vial is closed tightly and heated at 80°C for 20 hours. After cooling, the headspace sample containing IPCl and/or IPBr is ready for Cl- as well as Br-CSIA. TU Darmstadt has developed a simple and precise method for Cl-CSIA and Br-CSIA for IPCl and IPBr. The Cl- and Br-CSIA is carried out using a standard GC/quadruple MS online connected to a Purge and Trap for sample enrichment. IPCl, IPBr and possible residue in a sample were separated in GC. Then, the peak signal intensities of the masses of 63, 65, 78 and 80 for IPCl also the masses of 122 and 124 for IPBr were determined in SIM mode in qMS. Using a set of unique mathematical equations developed in this study, the chlorine and bromine isotope ratios for these compounds are determined. The precision of ± 0,5 ‰ or better was achieved for both Cl-CSIA and Br-CSIA under optimized conditions. This is the first method that enables Cl-CSIA for IPCl as well as Br-CSIA for IPBr using GC/qMS

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