Rapid measurement of perchlorate in polar ice cores down to sub-ng L−1 levels without pre-concentration
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An ion chromatography-electrospray ionization-tandem mass spectrometry (IC-ESI-MS/MS) method has been developed for rapid and accurate measurement of perchlorate in polar snow and ice core samples in which perchlorate concentrations are expected to be as low as 0.1 ng L−1. Separation of perchlorate from major inorganic species in snow is achieved with an ion chromatography system interfaced to an AB SCIEX triple quadrupole mass spectrometer operating in multiple reaction monitoring mode. Under optimized conditions, the limit of detection and lower limit of quantification without pre-concentration have been determined to be 0.1 and 0.3 ng L−1, respectively, with a linear dynamic range of 0.3–10.0 ng L−1 in routine measurement. These represent improvements over previously reported methods using similar analytical techniques. The improved method allows fast, accurate, and reproducible perchlorate quantification down to the sub-ng L−1 level and will facilitate perchlorate measurement in the study of natural perchlorate production with polar ice cores in which perchlorate concentrations are anticipated to vary in the low and sub-ng L−1 range. Initial measurements of perchlorate in ice core samples from central Greenland show that typical perchlorate concentrations in snow dated prior to the Industrial Revolution are about 0.8 ng L−1, while perchlorate concentrations are significantly higher in recent (post-1980) snow, suggesting that anthropogenic sources are a significant contributor to perchlorate in the current environment.
KeywordsIce core Ion chromatography-tandem mass spectrometry Perchlorate Pollution Ultra-trace analysis
Funding for this work was provided by US National Science Foundation (Award 1203533; Major Research Instrumentation Award 0922816 for the acquisition of AB SCIEX QTRAP 5500 tandem mass spectrometer). We would like to thank the South Dakota State University Campus Mass Spectrometry Facility and Linhong Jing for technical support and maintenance of the QTRAP 5500 mass spectrometer. We are grateful to Brian Logue, Robert Oda, Randy Jackson, Michael Stutelberg, Brendan Mitchell, and Erica Manandhar, of the Department of Chemistry and Biochemistry, South Dakota State University, for their assistance in this project.
Conflict of Interest
The authors declare that they have no conflict of interests.
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