title: Optimized demineralization technique for the measurement of stable isotope ratios of nonexchangeable H in soil organic matter.
abstract: To make use of the isotope ratio of nonexchangeable hydrogen (δ(2)H(n (nonexchangeable))) of bulk soil organic matter (SOM), the mineral matrix (containing structural water of clay minerals) must be separated from SOM and samples need to be analyzed after H isotope equilibration. We present a novel technique for demineralization of soil samples with HF and dilute HCl and recovery of the SOM fraction solubilized in the HF demineralization solution via solid-phase extraction. Compared with existing techniques, organic C (C(org)) and organic N (N(org)) recovery of demineralized SOM concentrates was significantly increased (C(org) recovery using existing techniques vs new demineralization method: 58% vs 78%; N(org) recovery: 60% vs 78%). Chemicals used for the demineralization treatment did not affect δ(2)H(n) values as revealed by spiking with deuterated water. The new demineralization method minimized organic matter losses and thus artificial H isotope fractionation, opening up the opportunity to use δ(2)H(n) analyses of SOM as a new tool in paleoclimatology or geospatial forensics.
authors.affiliation: Geoecology, University of Tübingen, Rümelinstrasse 19-23, 72070 Tübingen, Germany. marc.ruppenthal@unituebingen.de
authors.forename: Marc
authors.initials: M
authors.lastname: Ruppenthal
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Oelmann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wilcke
mesh_terms: D003903:Deuterium / Q000032:analysis; D006851:Hydrochloric Acid / Q000737:chemistry; D006858:Hydrofluoric Acid / Q000737:chemistry; D006859:Hydrogen / Q000032:analysis*; D008903:Minerals / Q000302:isolation & purification*; D009930:Organic Chemicals / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D052616:Solid Phase Extraction / Q000379:methods*
chemical_list: D008903:Minerals; D009930:Organic Chemicals; D012987:Soil; D006859:Hydrogen; D003903:Deuterium; D006851:Hydrochloric Acid; D006858:Hydrofluoric Acid