Application of a selective extraction method. for methylmercury compound specific stable. isotope analysis (MeHg CSIA) in biological.

Transcription

1 1 Supplementary information for Application of a selective extraction method for methylmercury compound specific stable isotope analysis (MeHg CSIA) in biological materials 6 7 Jeremy Masbou* a, David Point a, Jeroen E. Sonke a a Observatoire Midi Pyrénées, Laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université Paul Sabatier Toulouse 3, 14 avenue Edouard Belin, Toulouse, France RECEIVED DATE 15 *Author for correspondence: jeremy.masbou@get.obs mip.fr 16 Phone: +33 (0)

2 17 18 Table S1: GC/ICPMS parameters used in ID-GC-ICPMS analytical method GC conditions ID GC ICPMS Column RTX 5MS fused silica 30 m. id 0.25 mm. D.f. 0.25µm. Injection port PTV Splitless Injection port temperature 250 C Injection volume 2 µl Carrier gas flow He 0.8 ml min 1 Make up gas flow Ar 0.7 L min 1 Oven program Initial temperature 40 C Initial time 1.5 min Ramp rate 50 C min 1 Final temperature 250 C Hold time 1.5 min Transfer line Temperature 250 C Length 0.5 m ICPMS conditions Rf power 1200 W Gas flow Cool 16 L min 1 Auxiliary 0.8 L min 1 Nebulizer 0.45 L min 1 19 Isotopes/dwell times Hg : 196, 198, 199, 200, 201, 202, 204 (40ms) Tl : 203, 205 (30ms) 2

3 Limit of detection (LoD) We obtained LoD=0.05 ng.g 1 and LoD= ng.g 1 on ID GC ICPMS and CV AFS measurements respectively for MMHg quantification. LoD values were determined on whole extraction blanks including all reagent contributions. Considering optimal extraction conditions on 1g of sample and 6 ml of toluene, we estimate the LoD sample to 1.25 ng.g 1 (ID GC ICPMS) and LoD sample to 0.19 ng.g 1 (CV AFS). These values represent the theoretical minimum amount of MeHg in dry sample required to be detected by with the two methods. In this study, the minimum MeHg concentration was 208 ng.g 1 (BCR 414) Description of the biological certified reference materials (CRM s) DOLT 4 and TORT 2 are freeze dried CRMs provided by the National Research Council Canada (NRCC). They consist in defatted dogfish liver and lobster hepatopancreas respectively. DOLT 4 presents a HgT concentration of 2.58±0.22 µg.g 1, 10 times higher than 0.27±0.06 µg.g 1 of TORT 2. Both present MeHg/HgT ratio close to 0.5. Particularity for these materials is the lipid removal process performed during the manufacturing process BCR 463 and ERM CE464 are provided freeze dried by the Institute for Reference Materials and Measurements (IRMM). They differ with the previous CRMs presenting a non defatted tuna fish muscle matrix. HgT concentrations are higher; they reach 2.85±0.16 µg.g 1 and 5.24±0.10 µg.g 1 respectively. MeHg is the predominant form, resulting in a MeHg/HgT ratio above

4 BCR 414 is another freeze dried CRM provided by the IRMM. It consists in a mix of phyto and zooplankton coming from a river environment. HgT certified concentration reach 0.276±0.018 µg.g 1. No Hg speciation certified data were available from the provider. MeHg concentration of 0.208±0.008 µg.g 1 have been determined by ID GC ICPMS in a recent publication 1. We used this value for recovery calculations in our study SRM 1947 and NIST QC03LH03 are fresh frozen (FF) materials provided by the National Institute of Standards and Technology (NIST). SRM 1947 is a Lake Michigan trout tissue presenting a HgT concentration of 0.254±0.005 µg.g 1 for a [MeHg]/[HgT] ratio of NIST QC03LH03 is a pygmy sperm whale liver material sampled close to Sullivans Island (Charleston County, USA). No certification have been provided on this material but a consensus HgT value of 3.56±0.67 µg.g 1 has been determined in a recent interlaboratory comparison 2. For MeHg concentration, we used data obtained routinely in our laboratory by microwave TMAH extraction followed by ID GC ICPMS 3. We obtained [MeHg]=0.99±0.03 µg.g 1 and a low [MeHg]/[HgT] ratio of

5 62 63 Table S2: Hg isotopic data obtained for Hg intercomparison standard compared to previously reported measurements. 64 Reference materials Intercomparison Hg standard (UM Almaden) Bergquist and Blum Measured 20 n δ 199 Hg δ 200 Hg δ 201 Hg δ 202 Hg Δ 199 Hg Δ 200 Hg Δ 201 Hg ±2SD ±2SD ±2SD ±2SD ±2SD ±2SD ±2SD ( ) ( ) ( ) ( ) ( ) ( ) ( ) ±0.06 ±0.04 ±0.07 ±0.08 ±0.05 ±0.02 ± ±0.11 ±0.14 ±0.11 ±0.12 ±0.09 ±0.10 ± Table S3: MeHg standard solution inter calibration. [MeHg] corresponds to re calculated concentrations of the initial MeHg standard stock solution applying dilution factors to ID GC ICPMS and CV AFS measurements. Analytical Calibration n [MeHg]±SD [MeHg] purity yield±sd Method (ng.g 1 ) (%) Calculation > 96 ID GC ICPMS Internal calibration 201 MeHg Spike ± ±0.1 CV AFS External calibration NIST ±

6 Figure S1: Linear relations between Δ 199 Hg and Δ 201 Hg for the two Hg fractions, HgT and MeHg respectively. All biological CRMs have been plotted (sea Figure S1), except SRM 1947 which display a Δ 199 Hg HgT =5.26±0.07 ( Mean±2SD) far from the t others causing highh bias in regression determination. 2SD on the slopes have been calculated using best fit York Regression (with error in x and y). The dashed line represents the regression for HgT while the continuous line is for the MeHg fraction References V. Taylor, B. Jackson and C. Chen, Analytical and Bioanalytical Chemistry,, 2008, 392, DOI: / s S. Christopher, R. Pugh, M. Ellisor, E. Mackey, R. Spatz, B. Porter, K. Bealer, J. Kucklick, T. Rowles and P. Becker, Accred Qual Assur, 2007, 12, DOI: /s M. Monperrus, R. C. Rodriguez Martin Doimeadios, J. Scancar, D. Amouroux and O. F. X. Donard, Analytical Chemistry, 2003, 75, DOI: /ac B. A. Bergquist and J. D. Blum, Science, 2007, 318, DOI: D /science