TY - JOUR
T1 - Experimental evaluation of sampling, storage and analytical protocols for measuring arsenic speciation in sulphidic hot spring waters
AU - Hug, Katrin
AU - MAHER, Bill
AU - FOSTER, Simon
AU - Krikowa, Frank
AU - Moreau, John
N1 - Funding Information:
We thank Waiotapu Wonderland and the Ngāti Tahu Ngāti Whaoa Runanga for access to Champagne Pool, and ongoing logistical support for this project. We also thank Matthew Stott and Karen Houghton at GNS Science, New Zealand, for field support during sampling. We acknowledge the funding provided for writing this publication by the Albert Shimmins Memorial Fund ( UTR7.220 ) to K.H. and Dyason Fellowship to J.W.M.
Publisher Copyright:
© 2016 Elsevier B.V.
Copyright:
Copyright 2016 Elsevier B.V., All rights reserved.
PY - 2017/1/1
Y1 - 2017/1/1
N2 - Recently developed analytical techniques allowed for the detection of a range of dissolved arsenic-sulphur species in sulphur-rich environments. These so called thioarsenates are unstable, however, and can degrade upon handling and storage. An experiment evaluating the effect of exposure to air on arsenic and sulphur-enriched geothermal waters demonstrated a near to complete loss of thioarsenate species to arsenite or arsenate during short oxidation times. In contrast, thioarsenic standards were stable for the duration of analysis in spite of exposure to air. For samples containing thio-methylated arsenic species, the extent of oxidation varied for different methylated arsenic species. This study recommends flash freezing of samples in liquid nitrogen immediately after recovery and further storage under anaerobic conditions at − 80 °C. A second experiment to test the efficiencies of different HPLC columns for separating arsenic species resulted in the preference for an IonPac column with NaOH as the mobile phase when analysing arsenic thioanions, over the commonly used PEEK PRP-X100 anion exchange and Atlantis C18 reverse phase column with ammonium phosphate mobile phases. Distinct separation of thio-methylated arsenic species with the IonPac column, however, was not successful potentially due to matrix components. Acceptable detection, separation and quantification of thio-methylated arsenic species were only achieved with the Atlantis C18 column. This study shows that preservation and analysis of samples is matrix dependent, which holds important implications for efforts to interpret arsenic speciation in geothermal waters, especially those of low pH (2–3), low oxygen (≤ 49% saturation), low iron (≤ 5 mg L
− 1) and high sulphur concentrations (≥ 91 mg L
− 1).
AB - Recently developed analytical techniques allowed for the detection of a range of dissolved arsenic-sulphur species in sulphur-rich environments. These so called thioarsenates are unstable, however, and can degrade upon handling and storage. An experiment evaluating the effect of exposure to air on arsenic and sulphur-enriched geothermal waters demonstrated a near to complete loss of thioarsenate species to arsenite or arsenate during short oxidation times. In contrast, thioarsenic standards were stable for the duration of analysis in spite of exposure to air. For samples containing thio-methylated arsenic species, the extent of oxidation varied for different methylated arsenic species. This study recommends flash freezing of samples in liquid nitrogen immediately after recovery and further storage under anaerobic conditions at − 80 °C. A second experiment to test the efficiencies of different HPLC columns for separating arsenic species resulted in the preference for an IonPac column with NaOH as the mobile phase when analysing arsenic thioanions, over the commonly used PEEK PRP-X100 anion exchange and Atlantis C18 reverse phase column with ammonium phosphate mobile phases. Distinct separation of thio-methylated arsenic species with the IonPac column, however, was not successful potentially due to matrix components. Acceptable detection, separation and quantification of thio-methylated arsenic species were only achieved with the Atlantis C18 column. This study shows that preservation and analysis of samples is matrix dependent, which holds important implications for efforts to interpret arsenic speciation in geothermal waters, especially those of low pH (2–3), low oxygen (≤ 49% saturation), low iron (≤ 5 mg L
− 1) and high sulphur concentrations (≥ 91 mg L
− 1).
KW - Arsenic speciation
KW - HPLC
KW - ICP-MS
KW - Preservation
KW - Thioarsenate
UR - http://www.scopus.com/inward/record.url?scp=84987657574&partnerID=8YFLogxK
U2 - 10.1016/j.microc.2016.08.008
DO - 10.1016/j.microc.2016.08.008
M3 - Article
SN - 1095-9149
VL - 130
SP - 162
EP - 167
JO - Microchemical Journal
JF - Microchemical Journal
ER -