title: Oxygen isotope analyses of biogenic opal and quartz using a novel microfluorination technique.
abstract: BACKGROUND
  Measuring δ(18)O values in silicates is difficult and hazardous in comparison with measurements of carbonate minerals due to the difficulty in breaking Si-O-Si bonds. A novel method for measurement of δ(18)O values from quartz and biogenic silica utilizing high-temperature pyrolysis with continuous-flow isotope ratio mass spectrometry (CF-IRMS) is presented.
  
  
  METHODS
  Samples were prepared by offline dehydroxylation/dehydration under vacuum at 1060°C. The dehydroxylated samples are mixed with polytetrafluoroethylene (PTFE) powder (2.3:1 PTFE/Si) and graphite in silver foil capsules and reacted in a vario PYRO cube TC/EA system in a glassy carbon reaction tube. Quartz and biogenic opal samples react with available carbon in a microfluorination environment upon decomposition of the PTFE, producing CO for analysis via CF-IRMS.
  
  
  RESULTS
  Silicate samples reacted quantitatively, producing data with yields ≥88% from ~400 µg samples. Multiple analyses with international standards demonstrated accuracy for replicate measurements (1σ range ±0.3-0.6‰), comparing favorably with previously published techniques.
  
  
  CONCLUSIONS
  New data produced with the microfluorination technique are comparable with data from studies using existing methodologies. The microfluorination technique has the potential to greatly increase the number of laboratories producing silicate oxygen isotope data for mineralogic, paleoclimatic and biogeochemical applications.
authors.affiliation: Department of Geology and Stable Isotope Laboratory, University of California, Davis, Davis, CA 95616, USA. ajmenicucci@gmail.com
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Menicucci
authors.forename: Joy A
authors.initials: JA
authors.lastname: Matthews
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Spero
mesh_terms: D017377:Diatoms / Q000737:chemistry*; D005580:Fossils; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D010103:Oxygen Isotopes / Q000737:chemistry; D011791:Quartz / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry
chemical_list: D010103:Oxygen Isotopes; D011791:Quartz; D012822:Silicon Dioxide