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Improvement of analytical method for chlorine dual-
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inlet isotope ratio mass spectrometry of
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organochlorines.
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Tetyana Gilevska,¥ Natalija Ivdra,¥,† Magali Bonifacie,‡ Hans-Hermann
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Richnow¥,†
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¥
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UFZ, Permoserstr. 15, D-04318 Leipzig, Germany
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research -
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†
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Germany
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‡
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Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, F-75005 Paris, France
Isodetect GmbH – Company for Isotope Monitoring, Deutscher Platz 5b, D-04103 Leipzig,
Group of the Geochemistry of Stable Isotopes, The Institute of Earth Physics of Paris,
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SUPPORTING INFORMATION
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CONTENT
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1. Initial procedure for conversion of -HCH to CH3Cl…………………………………..…………………….S-2
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2. Method for the conversion of AgCl to MeCl…………………………………………………….……………….S-2
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3. Gas Chromatography Mass Spectrometry (GC/MS)….………………………………………………….… S-3
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4. Ion Chromatography…………………………………………………………………...…………………………………..….S-4
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5. Optimization of the water volume for the dissolution…………………..………………………………..….S-4
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Table S-1. Optimization of water volume with CuCl…………………………………………………………. S-5
S-1
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1. Initial procedure for conversion of -HCH to AgCl
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The organic chlorine of -HCH was converted to AgCl following a procedure modified from
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those reported elsewhere.[1-3] 1.8 g of pre-heated copper (II) oxide (CuO) were loaded into
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quartz ampule, followed by the addition of 12.12 mg of crystalline -HCH (41.7 mol,
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corresponding to 250 mol or 8.8 mg of Cl). The air was evacuated from the ampule down to
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100 mbar, while the lower part of the ampule, containing the sample and CuO, was immersed
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in liquid nitrogen to avoid evaporation of -HCH. The ampule was then sealed and heated in
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the furnace by increasing the temperature at 5 °C/min to 620 °C, and oxidation of the organic
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compounds was then carried out at 620 °C for 1 h. The ampule was then cooled slowly to
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room temperature, cracked at the top, filled with 15 mL ultra-high purity water and vortex-
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mixed to dissolve the formed inorganic chlorides. The ampule was then left for 2 days for the
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complete dissolution of the chlorides. The vortex-mixed solution was filtered through a nylon
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filter (0.22 m) and the residues were washed with an additional 10 mL of water and then
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filtered to obtain 25 mL of combined extract. The solution obtained was poured into a flask
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containing 2.5 g of KNO3- and was buffered at pH 2.2 using 0.56 g of citric acid*H2O and
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0.0175 g of Na2HPO4*2H2O), both in dry form. The solution was then heated at 80 °C for
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approximately 30 min and 3.75 mL of 1M AgNO3 solution was added to precipitate AgCl.
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The solution was cooled down for 1 h, and the precipitate was filtered on a glass microfiber
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filter and dried in the dark at room temperature.
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2. Method for the conversion of AgCl to CH3Cl
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The method applied was that described by Eggenkamp[4] and Godon[5] and routinely used at
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IPGP.[6] Briefly, the filter with AgCl was placed in the borosilicate glass tube and excess of
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CH3I (100 L) was added. For the conversion of AgCl to CH3Cl the tube was sealed and
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heated to 80 °C for 72 h. The CH3Cl was then separated from the excess CH3I by gas
S-2
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chromatography on two subsequent packed columns filled with Porapak Q 80-100 mesh (each
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column with a length of 2 m and an outer diameter of 3.175 mm), using dry pure He at 130°C,
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2.1 bar and 15 mL/min. A thermal conductivity detector was used to check the progress of the
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purification. The pure CH3Cl was then separated cryogenically, transferred to a cold finger
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under vacuum, and quantified with a calibrated pressure gauge to confirm quantitative
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transformation at all purification steps, thus preventing any isotopic fractionation. The CH3Cl
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was then transferred to a sample tube and introduced into the mass spectrometer for 37Cl
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measurements by DI-IRMS.
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3. Gas Chromatography Mass Spectrometry (GC/MS)
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GC/MS analysis of the residues after combustion was performed to test the conversion of -
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HCH to CuCl. The GC/MS system consisted of a gas chromatograph (7890A, Agilent
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Technologies, Palo Alto, CA, USA) coupled to a 5975C Mass Selective Detector mass
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spectrometer (Agilent Technologies). Extracts of the target compounds in organic solvents
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were directly injected into the system by a CTC-Combi Pal-auto sampler (CTC, Zwingen,
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Switzerland) via a split-splitless GC-injector. The injector temperature was 280 °C., and the
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target compounds were separated using a HP-5 capillary column (30 m x 0.32 mm ID x 0.25
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µm FD; Agilent Technologies). The oven temperature program for the separation of -HCH
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and its potential breakdown products started at 35°C, was held for 5 min isothermally,
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increased at 20 °C/min to 110 °C, then at 1 °C/min to 150 °C, then at 20°C/min to 230 °C,
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where it was held for 5 min, and finally increased at 20 °C/min to 320 °C. Helium was used as
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carrier gas with a flow rate of 2 mL/min. The mass spectrometer was operated in electron
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ionization mode and analyses were conducted in a full scan mode (m/z 50 to 500) for the
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analysis of organic components and Selected Ion Monitoring (SIM) mode for the
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quantification of unreacted -HCH. Traces of other isomers of HCH were observed, probably
S-3
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formed from -HCH via thermo-isomerization, as a side reaction of the combustion process.
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Thus, quantification of unreacted material was carried out by calculating peak areas from the
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SIM chromatograms, based on the 5 most abundant fragment ions of HCHs (m/z: 109.0,
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111.0, 181.0, 183.0 and 219.0). The concentrations of the organic compounds were compared
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with the concentrations in standard solutions, corresponding to 100%, 10% and 1% of
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unreacted material.
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4. Ion Chromatography (IC)
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IC analyses of the chlorine concentration were performed to investigate the chorine blanks
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and to determine the efficiency of the dissolution and precipitation steps. Analyses were
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performed at the Department of the Analytical Chemistry of the UFZ on an ICS-2000 gas
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chromatograph (Thermo Fisher Scientific, Bremen, Germany), equipped with IonPac AS18
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Guard and Analytical columns (4 mm, Dionex by Thermo Fisher Scientific). A KOH solution
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was used as an eluent at a flow rate at 1 mL/min at 30 °C, supplied by a EG III KOH
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potassium hydroxide eluent generator cartridge with a CR-ATC continuously regenerated
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anion trap (Dionex by Thermo Fisher Scientific). The concentration of the KOH solution was
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held at 22 mM for 6 min, then increased to 40 mM in 1.5 min where it was held for 7.5 min.
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The conductivity of the eluent was reduced by a self-regenerating suppressor ASRS ULTRA
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II (4 mm, Dionex by Thermo Fisher Scientific). The EN ISO 10304-1 method was used.[7]
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The limit of detection (LOD) was 0.07 mg/L and the limit of quantification (LOQ) was 0.21
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mg/L of chlorine.
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5. Optimization of the water volume for the dissolution
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Commercially available crystalline CuCl was mixed with 1.8 g of pre-heated CuO to mimic
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conditions after the combustion of organochlorines and the resulting mixture was suspended
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in different volumes of uhp-water (ratio mL H2O/mol Cl from 0.36 to 8.00, Table S-1). The
S-4
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optimal dissolution conditions (sonification for 2 h at 50 °C) determined in previous
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experiments were applied and different water/ CuCl ratios were compared by the chlorine
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recovery yields (Table S-1). The optimal water/ Cl ratio was determined as 0.4 mL/mol,
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resulting in 96% chlorine recovery.
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Table S-1. Optimization of water volume with CuCl
Ratio mL H2O/mol Cla
pH
Recovery of Cl (%)
8.00
5.5
84 ± 3
5.00
n.a.b
79 ± 6
2.00
5.5
76 ± 4
0.40
5.3
96 ± 6
0.36
n.a.
82 ± 6
0.43
n.a.
83 ± 7
0.28
5.1
57 ± 8
0.10
4.7
33 ± 6
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a
The ratio represents the relationship of the water volume to the amount of Cl, loaded for the dissolution
process in form of CuCl.
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data is not available
S-5
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REFERENCES
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[1]
L. Jendrzejewski, R. Littke, J. Rullkotter. Organic geochemistry and depositional
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history of Upper Albian sediments from the Kirchrode I borehole, northern Germany.
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Palaeogeogr. Palaeoclimatol. Palaeoecol. 2001, 174, 107.
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[2]
H. Holmstrand, P. Andersson, O. Gustafsson. Chlorine isotope analysis of
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submicromole organochlorine samples by sealed tube combustion and thermal
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ionization mass spectrometry. Anal. Chem. 2004, 76, 2336.
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[3]
C. Aeppli, D. Bastviken, P. Andersson, O. Gustafsson. Chlorine Isotope Effects and
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Composition of Naturally Produced Organochlorines from Chloroperoxidases, Flavin-
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Dependent Halogenases, and in Forest Soil. Environ. Sci. Technol. 2013, 47, 6864.
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[4]
H. G. M. Eggenkamp, Utrecht University 1994.
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[5]
A. Godon, N. Jendrzejewski, H. G. M. Eggenkamp, D. A. Banks, M. Ader, M. L.
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Coleman, F. Pineau. A cross-calibration of chlorine isotopic measurements and
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suitability of seawater as the international reference material. Chem. Geol. 2004, 207,
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1.
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[6]
M. Bonifacie, N. Jendrzejewski, P. Agrinier, M. Coleman, F. Pineau, M. Javoy.
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Pyrohydrolysis-IRMS determination of silicate chlorine stable isotope compositions.
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Application to oceanic crust and meteorite samples. Chem. Geol. 2007, 242, 187.
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[7]
International Organization for Standardization, ISO/TC 147/SC 2, 2007.
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