RATIONALE: Measurement of δ(2) H values in non-exchangeable-H (δ(2) H(n)) and δ(18)O values in organic environmental samples are inconsistent among laboratories worldwide due to varied and lengthy approaches in controlling for H isotope exchange (for δ(2)H(n) values) and removal of trace moisture (δ(2)H(n) and δ(18)O values), which undermines the comparability of organic δ(2)H and δ(18)O data produced among different laboratories. METHODS: An online preparation system was developed for the measurement of the δ(2)H(n) and δ(18)O values of organic samples, coupled to isotope-ratio mass spectrometers. The system features a 50-position autosampler and isolation valve where (1) the samples are held isothermal between ambient to 40-120 ± 0.1 °C for H isotopic exchange experiments (δ(2) H(n)) and drying of hygroscopic samples (δ(2) H(n) and δ(18)O), (2) the samples are evacuated to <5 mbar and flushed with helium for moisture and N(2) removal, and (3) injection of up to 500 μL of H(2)O is possible for controlled vapour exchangeable-H experiments. RESULTS: The system provides highly reproducible and precise δ(2)H(n) isotope estimates for a range of organic keratinous standard powders over a wide range of experimental temperatures. A reproducible sample processing regimen can now be applied to a wider range of organics and hygroscopic samples that are currently hampered by poorly controlled preparative methods amongst laboratories. CONCLUSIONS: Rapid and reproducible online vacuum equilibration of samples and standards for the routine measurement of δ(2)H(n) and δ(18)O values is now possible using the online equilibration system, with the added benefit that sample processing times for organic δ(2)H values are reduced from weeks to hours.
RATIONALE: Measurement of δ(2) H values in non-exchangeable-H (δ(2) H(n)) and δ(18)O values in organic environmental samples are inconsistent among laboratories worldwide due to varied and lengthy approaches in controlling for H isotope exchange (for δ(2)H(n) values) and removal of trace moisture (δ(2)H(n) and δ(18)O values), which undermines the comparability of organic δ(2)H and δ(18)O data produced among different laboratories. METHODS: An online preparation system was developed for the measurement of the δ(2)H(n) and δ(18)O values of organic samples, coupled to isotope-ratio mass spectrometers. The system features a 50-position autosampler and isolation valve where (1) the samples are held isothermal between ambient to 40-120 ± 0.1 °C for H isotopic exchange experiments (δ(2) H(n)) and drying of hygroscopic samples (δ(2) H(n) and δ(18)O), (2) the samples are evacuated to <5 mbar and flushed with helium for moisture and N(2) removal, and (3) injection of up to 500 μL of H(2)O is possible for controlled vapour exchangeable-H experiments. RESULTS: The system provides highly reproducible and precise δ(2)H(n) isotope estimates for a range of organic keratinous standard powders over a wide range of experimental temperatures. A reproducible sample processing regimen can now be applied to a wider range of organics and hygroscopic samples that are currently hampered by poorly controlled preparative methods amongst laboratories. CONCLUSIONS: Rapid and reproducible online vacuum equilibration of samples and standards for the routine measurement of δ(2)H(n) and δ(18)O values is now possible using the online equilibration system, with the added benefit that sample processing times for organic δ(2)H values are reduced from weeks to hours.
Authors: Isabella C C von Holstein; Penelope Walton Rogers; Oliver E Craig; Kirsty E H Penkman; Jason Newton; Matthew J Collins Journal: PLoS One Date: 2016-10-20 Impact factor: 3.240
Authors: Roy Faiman; Adama Dao; Alpha Seydou Yaro; Moussa Diallo; Samake Djibril; Zana Lamissa Sanogo; Yossi Ousmane; Margery Sullivan; Laura Veru; Benjamin J Krajacich; Asha Krishna; Joy Matthews; Christine A M France; Gabriel Hamer; Keith A Hobson; Tovi Lehmann Journal: Methods Ecol Evol Date: 2019-05-17 Impact factor: 7.781