Measurements of ionic species within Antarctic ice cores contributes to better knowledge of the Earth's climate history. However, the amount of those samples required for each analysis — about 1-5 millilitres, using standard-ion chromatography (IC)— is nowadays impractical given the high value of each sample and the huge demand for the aliquots generated.
Our ACROSS team met with Australian Antarctic Division (AAD) scientists who asked for a new capability which was able to reduce the amount of sample required for each analysis. We realised we could solve the challenge using the analytical technology already available in ACROSS.
ACROSS forms an Australian consortium of prominent researchers in separation science and AAD is responsible for leading, coordinating and delivering the Australian Antarctic program.
Aims & Objectives
Currently, there is a clear demand for ever-greater temporal resolution from the scientists modelling ice core data. However, the nature of the sample itself is such that greater temporal resolution can only be achieved through increased sample analysis per ice core unit volume. In this study our main objective was to develop the analytical capability to move our temporal resolution from yearly cycles, down to seasonal and potentially monthly data.
In pursuit of a reduction of the amount of ice core sample required for each analysis, this collaborative team decided to investigate the potential of capillary scale ion chromatography, which requires 10-100 fold less sample volume per analysis.
A new analytical method was developed, capable of reducing the sample volume required per analysis to just 40 microliters. Coupling this capillary based technology with mass-spectrometry detection provided greater method sensitivity and selectivity for target anionic proxies in the samples of interest. This new analytical capability was then applied to the analysis of samples of interest to the partner Antarctic scientists.
We improved the Cap-IC method using mass-spectrometry detection, which is more specific and sensitive. New methods were validated by analysing samples originating from the Aurora Basin, Antarctica.
We set ourselves six months to achieve our objectives. Our approach was to first validate the new Cap-IC method developed at the beginning of this Ian Potter Foundation project, analysing ~125 snow pit test samples from the Antarctic Aurora Basin site, which had been previously analysed using a former standard-IC method.
Secondly, the capillary based system was coupled to the mass-spectrometry (MS) detector and optimized for the identification and quantification of primary proxy targets in this work, one of which was methanesulfonic acid, a key anionic proxy for the annual cycling of Antarctic sea ice.
The new couple technology was then further applied to the analysis of a selection of the same snow pit samples analysed previously, providing a comparative study of the three analytical methods, old and new. A statistical study was carried out to assess the degree of agreement among the traditional and the new methods.
Going beyond the significant advantages of the Cap-IC method, specifically the small amount of sample required, the coupled mass-spectrometric method reduced the limits of detection for methanesulfonate to just 0.7 micrograms per litre, this being the lowest reported in the literature until now. In addition, this work generated the first fluoride ion profile for this important series of Aurora Basin snow pit samples which provides information about volcanic activity from surrounding areas.
The outcomes of the project, have been a complete success: with one scientific publication in Chromatography Today journal, one oral talk and two posters at two prestigious international Conferences, IPICS 2016 and HPLC 2016, in just 6 months.
Additionally, the considerable general interest around environmental processes and climatic change resulted in two organisations (Thermo Fisher Scientific and LCGC -Cromatography Online) making contact with our investigation group in order to solicit two published interviews based on the work being carried out.
By coupling Cap-IC to mass-spectrometry, we were able to reach the lowest limits of detection for methanesulfonate reported in the literature until now and to improve the specificity. The statistical study for the comparison of the methods showed that the Cap-IC and Cap-IC-MS methods can be used interchangeably with the standard-IC method as they are comparable and work well together.
We plan to carry out a deeper study of the data acquired by the Cap-IC-MS method, publish a new article and we hope to further exploit the technology we have developed by analysing Australia's million year ice core samples.
Written by Dr Estrella Sanz, Australian Centre for Research on Seperation Science (ACROSS)
This project has had excellent outcomes in terms of scientific data as well as for Dr Sanz's research in terms of exposure and dissemination. The considerable general interest this project has created around environmental processes and climatic change resulted in interviews in two of the most well-read journals in the field of Chromatography.
Nicole Bortone, Science Program Manager