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Ocean Science An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 6 | Copyright
Ocean Sci., 11, 947-952, 2015
https://doi.org/10.5194/os-11-947-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Technical note 07 Dec 2015

Technical note | 07 Dec 2015

Technical note: Could benzalkonium chloride be a suitable alternative to mercuric chloride for preservation of seawater samples?

J. Gloël2,1, C. Robinson1, G. H. Tilstone2, G. Tarran2, and J. Kaiser1 J. Gloël et al.
  • 1Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
  • 2Plymouth Marine Laboratory, The Hoe, Plymouth, UK

Abstract. Instrumental equipment unsuitable or unavailable for fieldwork as well as lack of ship space can necessitate the preservation of seawater samples prior to analysis in a shore-based laboratory. Mercuric chloride (HgCl2) is routinely used for such preservation, but its handling and subsequent disposal incur environmental risks and significant expense. There is therefore a strong motivation to find less hazardous alternatives. Benzalkonium chloride (BAC) has been used previously as microbial inhibitor for freshwater samples. Here, we assess the use of BAC for marine samples prior to the measurement of oxygen-to-argon (O2 / Ar) ratios, as used for the determination of biological net community production. BAC at a concentration of 50 mg dm−3 inhibited microbial activity for at least 3 days in samples tested with chlorophyll a (Chl a) concentrations up to 1 mg m−3. BAC concentrations of 100 and 200 mg dm−3 were no more effective than 50 mg dm−3. With fewer risks to human health and the environment, and no requirement for expensive waste disposal, BAC could be a viable alternative to HgCl2 for short-term preservation of seawater samples, but is not a replacement for HgCl2 in the case of oxygen triple isotope analysis, which requires storage over weeks to months. In any event, further tests on a case-by-case basis should be undertaken if use of BAC was considered, since its inhibitory activity may depend on concentration and composition of the microbial community.

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We assess benzalkonium chloride (BAC) as alternative to mercuric chloride (HgCl2) for preservation of seawater samples. BAC concentrations of 50mg dm–3 inhibited microbial activity for at least 3 days in samples tested with chlorophyll a concentrations up to 1mg m–3. With fewer risks to health and environment, and lower waste disposal costs, BAC could be a short-term alternative to HgCl2, but cannot replace it for oxygen triple isotope samples, which require storage over weeks to months.
We assess benzalkonium chloride (BAC) as alternative to mercuric chloride (HgCl2) for...
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