Isotopic analysis on nanogram quantities of carbon from dissolved insect cuticle: a method for paleoenvironmental inferences

Yongtao Zhao, David M. Nelson, Benjamin F. Clegg, Cheng Bang An, Feng Sheng Hu

Research output: Contribution to journalArticle

Abstract

Rationale: Carbon isotope (δ13C) data from arthropod cuticles provide invaluable information on past and present biogeochemical processes. However, such analyses typically require large sample sizes that may mask important variation in δ13C values within or among species. Methods: We have evaluated a spooling-wire microcombustion (SWiM) device and isotope ratio mass spectrometry (IRMS) to measure the δ13C values of carbon dissolved from the cuticle of chitinous aquatic zooplankton. The effects of temperature, pH, and reaction time on the δ13C values of acid-dissolved bulk cuticle and purified chitin fractions obtained from a single species of chironomid from four commercial suppliers were assessed. These results were compared with baseline δ13C values obtained on solid cuticle using conventional EA (elemental analyzer)/IRMS. Results: The results indicate differential, time-dependent dissolution of chitin, lipid and protein fractions of cuticle concomitant with slow depolymerization and deacetylation of chitin. Isotopic offsets between dissolved bulk head capsules and a purified chitin fraction suggest the contributions of other isotopically lighter components of the bulk head capsules to bulk chitin extracts. The SWiM/IRMS δ13C results obtained on dissolved cuticle using a treatment of 4 N HCl at 25 °C for 24 h produced generally stable δ13C values, large sample/blank CO2 yields and a positive correlation with conventional EA/IRMS results on unprocessed cuticle. Conclusions: The SWiM/IRMS system offers a reliable method to determine δ13C values on nanogram quantities of carbon from dissolved insect cuticle, thus reducing sample size requirements and providing new opportunities to use δ13C variation among/within species for reconstructing paleo-biogeochemical processes.

Original languageEnglish (US)
Pages (from-to)1825-1834
Number of pages10
JournalRapid Communications in Mass Spectrometry
Volume31
Issue number21
DOIs
StatePublished - Nov 15 2017

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry

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