An inter-laboratory investigation of the Arctic sea ice biomarker proxy IP 25 in marine sediments: key outcomes and recommendations

• Published in: Climate of the Past
• Main Authors: S. T. Belt, T. A. Brown, L. Ampel, P. Cabedo-Sanz, K. Fahl, J. J. Kocis, G. Massé, A. Navarro-Rodriguez, J. Ruan, Y. Xu
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2014
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; Antarctic; Antarctic Peninsula; Arctic; Southern Ocean; The Antarctic; Antarc*; Iceland; Sea ice
• Online Access: https://doi.org/10.5194/cp-10-155-2014; https://doaj.org/article/1262f846785f4ade8289bda9bb322908

We describe the results of an inter-laboratory investigation into the identification and quantification of the Arctic sea ice biomarker proxy IP 25 in marine sediments. Seven laboratories took part in the study, which consisted of the analysis of IP 25 in a series of sediment samples from different regions of the Arctic, sub-Arctic and Antarctic, additional sediment extracts and purified standards. The results obtained allowed 4 key outcomes to be determined. First, IP 25 was identified by all laboratories in sediments from the Canadian Arctic with inter-laboratory variation in IP 25 concentration being substantially larger than within individual laboratories. This greater variation between laboratories was attributed to the difficulty in accurately determining instrumental response factors for IP 25 , even though laboratories were supplied with appropriate standards. Second, the identification of IP 25 by 3 laboratories in sediment from SW Iceland that was believed to represent a blank, was interpreted as representing a better limit of detection or quantification for such laboratories, contamination or mis-identification. These alternatives could not be distinguished conclusively with the data available, although it is noted that the precision of these data was significantly poorer compared with the other IP 25 concentration measurements. Third, 3 laboratories reported the occurrence of IP 25 in a sediment sample from the Antarctic Peninsula even though this biomarker is believed to be absent from the Southern Ocean. This anomaly is attributed to a combined chromatographic and mass spectrometric interference that results from the presence of a di-unsaturated highly branched isoprenoid (HBI) pseudo-homologue of IP 25 that occurs in Antarctic sediments. Finally, data are presented that suggest that extraction of IP 25 is consistent between Accelerated Solvent Extraction (ASE) and sonication methods and that IP 25 concentrations based on 7-hexylnonadecane as an internal standard are comparable using these methods. ...