Determination of the concentration of carbonic species in natural waters: results from a world-wide proficiency test

Verma, Mahendra P. and Portugal, Enrique and Gangloff, Sophie and Armienta, Mana Aurora and Chandrasekharam, Dornadula and Sanchez, Mayela and Renderos, Roberto E. and Juanco, Miguel and van Geldern, Robert (2015) Determination of the concentration of carbonic species in natural waters: results from a world-wide proficiency test. Geostandards and Geoanalytical Research, 39 (2). pp. 233-255. ISSN 1639-4488

Abstract

The results of an international interlaboratory proficiency test for the determination of carbonic species are presented. Eight laboratories analysed twelve water samples (four synthetic waters, one lake water, four geothermal waters, one seawater and two petroleum waters) by two methods: (a) individual laboratory analytical procedure and (b) acid-base titration curves in tabular form following a standardised protocol. In case (b), the concentrations of carbonic species were calculated by the organiser using the (1) Hydrologists' method, (2) Geochemists' method and/or (3) initial pH and total alkalinity method. For synthetic waters, the averaged % trueness and precision of measurement of the two methods were (trueness = 7.6, precision = 9.4) and (9.0, 3.4) for total alkalinity, and (6.6, 31.0) and (7.8, 6.1) for carbonic alkalinity, respectively. This indicates that the total alkalinity calculation procedure is in general correct in the individual laboratory method, but the carbonic alkalinity calculation procedure has serious problems. The measurements of total alkalinity for lake and seawaters were in agreement in both the methods; however, the individual laboratory measurement method for geothermal and petroleum waters was conceptually incorrect. Thus, the analytical procedures for the determination of carbonic species were reviewed. To apply the Hydrologists' and/or Geochemists' methods, the location of NaHCO3EP and H2CO3EP is necessary, even for samples with pH lower than that of NaHCO3EP, and a backward titration curve after complete removal of CO2 must be performed. The initial pH and total alkalinity method is appropriate where a complete analysis of species that contribute to the alkalinity is known.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences (1 July 2013 - 5 Sept 2019)
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences (1 July 2013 - 5 Sept 2019)
Date Deposited: 02 Sep 2019 01:28
Last Modified: 13 Sep 2019 05:11
Uncontrolled Keywords: acid-base titration, analytical method, interlaboratory comparison, natural waters
Fields of Research : 05 Environmental Sciences > 0599 Other Environmental Sciences > 059999 Environmental Sciences not elsewhere classified
Identification Number or DOI: 10.1111/j.1751-908X.2014.00306.x
URI: http://eprints.usq.edu.au/id/eprint/35989

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