title: A comparison of freeze-drying and oven-drying preparation methods for bulk and compound-specific carbon stable isotope analyses: examples using the benthic macroinvertebrates Stenopsyche marmorata and Epeorus latifolium.
abstract: BACKGROUND
  Carbon stable isotope analysis of bulk samples and fatty acids is an established method for tracing carbon flow pathways and reconstructing trophic interactions, but there is no consensus on which sample drying method should be used for sample preparation. The aim of this study was to determine if freeze-drying and oven-drying treatments used to prepare samples of the benthic macroinvertebrates Stenopsyche marmorata and Epeorus latifolium for bulk and fatty-acid-specific carbon stable isotope analysis yield different isotopic ratio values.
  
  
  METHODS
  Five individuals each from two species were split in half; one half was freeze-dried and the other half was oven-dried. The samples were ground and the δ(13)C values of the bulk samples and eight fatty acids were measured following combustion using an isotope ratio mass spectrometer coupled to an elemental analyzer or gas chromatography system.
  
  
  RESULTS
  The mean difference in the bulk and fatty acid δ(13)C values between freeze-dried and oven-dried samples was small (≤0.1‰ in both cases), although relatively large variations were observed in individual fatty-acid-specific δ(13)C values (maximum of ≤0.9 ‰). There were no significant differences in either bulk sample or fatty-acid-specific δ(13)C values between freeze-dried or oven-dried samples of the same species.
  
  
  CONCLUSIONS
  Freeze-drying and oven-drying are equally acceptable methods for preparing freshly caught S. marmorata and E. latifolium samples for bulk and fatty-acid-specific carbon stable isotope analyses.
authors.affiliation: National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-0046, Japan.
authors.forename: Fumikazu
authors.initials: F
authors.lastname: Akamatsu
authors.affiliation: National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki, 305-8642, Japan.
authors.forename: Yaeko
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Research Institute for Humanity and Nature, 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8047, Japan.|Center for Ecological Research, Kyoto University, 2-509-3 Hirano, Otsu, Shiga, 520-2113, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kato
authors.affiliation: Research Institute for Humanity and Nature, 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8047, Japan.|Center for Ecological Research, Kyoto University, 2-509-3 Hirano, Otsu, Shiga, 520-2113, Japan.
authors.forename: Chikage
authors.initials: C
authors.lastname: Yoshimizu
authors.affiliation: Research Institute for Humanity and Nature, 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8047, Japan.|Center for Ecological Research, Kyoto University, 2-509-3 Hirano, Otsu, Shiga, 520-2113, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tayasu
mesh_terms: D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis*; D003890:Desiccation / Q000379:methods*; D065133:Ephemeroptera / Q000737:chemistry*; D005227:Fatty Acids / Q000737:chemistry; D005612:Freeze Drying / Q000379:methods*; D007313:Insecta / Q000737:chemistry; D007814:Larva / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D008954:Models, Biological
chemical_list: D002247:Carbon Isotopes; D005227:Fatty Acids