Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Journal of Chromatography A art. 460821 [8p.] Methylmercury Carbon isotopes Purge and trap Isotope ratio mass spectrometry 2020 fdi:010078979 ENG Journal of Chromatography A 0021-9673 ISI:000527316600008 10.1016/j.chroma.2019.460821 https://www.documentation.ird.fr/hor/fdi:010078979 https://www.documentation.ird.fr/intranet/publi/2020/05/010078979.pdf 1617 Horizon (IRD) Despite several decades of mercury research, answering fundamental questions on where and how methylmercury (CH3Hg) toxin is naturally produced in aquatic ecosystems, is still highly challenging. Investigating complex and/or coupled processes in the context of global changes requires new high-resolution analytical tools. The purpose of the compound specific carbon stable isotopic analysis (delta C-13-CSIA) of the methyl group of methylmercury (CH3Hg), is to explore how the carbon cycle contributes to CH3Hg sources and formation pathways. The main problem associated with recent CH3Hg delta C-13-CSIA methods is the limited sensitivity when using Liquid Injection (LI)-GC-C-IRMS techniques, requiring several micrograms of CH3Hg (as Hg). In this work, we present the development and application of an original Purge-&-Trap system (PT) coupled to a GC-C-IRMS with the purpose of transferring and analyzing the total amount of CH3Hg available in a sample vial in the low nanogram range. The new PT-GC-C-IRMS system enhance the sensitivity by a factor better than 200, relative to LI-GC-C-IRMS, by minimizing the sample mass requirements. The delta C-13(CH3Hg) values obtained, following the same sample derivatization approach coupled to PT-GC-C-IRMS (-53.5 +/- 1.9 %), were in good agreement with the ones obtained in a previous study (-53.8 +/- 1.1 %). The standard solution was prepared from the same salt, requesting only 25-200 ng of CH3Hg (as Hg). This new methodology represents a milestone towards the analysis of large array of biological samples displaying CH3Hg concentrations in the low-mid ng g(-1) range, in order to explore the meaning of the carbon stable isotopic signature of CH3Hg in the environment. 020 UR234