Isotopic analysis on nanogram quantities of carbon from dissolved insect cuticle: a method for paleoenvironmental inferences. (1st October 2017)

• Record Type: Journal Article
• Authors: Zhao, Yongtao; Nelson, David M.; Clegg, Benjamin F.; An, Cheng‐Bang; Hu, Feng Sheng
• Is Part Of: Rapid communications in mass spectrometry. Volume 31:Number 21(2017)
• Page Start: 1825
• Page End: 1834
• Publication Date: 2017-10-01
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.7965
• Languages: English
• ISSNs: 0951-4198

Abstract

Abstract : Rationale: Carbon isotope ( δ 13 C ) 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 δ 13 C values within or among species. Methods: We have evaluated a spooling‐wire microcombustion (SWiM) device and isotope ratio mass spectrometry (IRMS) to measure the δ 13 C values of carbon dissolved from the cuticle of chitinous aquatic zooplankton. The effects of temperature, pH, and reaction time on the δ 13 C 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 δ 13 C 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 δ 13 C results obtained on dissolved cuticle using a treatment of 4 N HCl at 25 °C for 24 h produced generally stable δ 13 C 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 δ 13 C values on nanogram quantities of carbon from dissolved insect cuticle, thus reducing sample size requirements and providing new opportunities to use δ 13 C variation among/within species for reconstructing paleo‐biogeochemical processes.