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Improved methodology for the microwave digestion of carbonate-rich environmental samples


Durand, A and Chase, Z and Townsend, AT and Noble, T and Panietz, E and Goemann, K, Improved methodology for the microwave digestion of carbonate-rich environmental samples, International Journal of Environmental Analytical Chemistry, 96, (2) pp. 119-136. ISSN 0306-7319 (2016) [Refereed Article]

Copyright Statement

2016 Taylor & Francis

DOI: doi:10.1080/03067319.2015.1137904


Microwave-assisted digestion permits a rapid and total dissolution of sediments and various other sample types, allowing easier and more accurate multi-element determinations. In this study, we present an optimised microwave digestion method for the complete digestion of 200mg of carbonate-rich sediments. The optimised method prevents the formation of precipitates and assures a complete dissolution of the material. The optimised method involves treatment with concentrated hydrochloric acid (HCl) prior to microwave digestion, which prevents the formation of an insoluble calcium fluoride precipitate associated with the use of hydrofluoric acid (HF). Three different certified reference samples along with a pure calcium carbonate standard and a carbonate-rich in-house marine sediment sample were considered. Sediments were found to only be partially digested if insufficient HF was present, while a noticeable fluoride-based precipitate was found if excess HF was present. Twenty elements were analysed using sector field inductively coupled plasma mass spectrometry (ICP-MS) (Al, Ag, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, Sr, Th, Ti, U, V and Zn). A total sample digestion with average elemental recoveries above 90% was obtained by reacting carbonate-rich samples with HCl on a hotplate at 150C for 2h (time for the total release of generated CO2), prior to any microwave digestion step. This extra step prevented the accumulation of gas in the sealed vessels during digestion, which would otherwise influence the carbonate chemical equilibria and make insoluble calcium available for precipitation. After this initial treatment, the improved digestion method consisted of microwave attack employing a mix of concentrated HCl, nitric acid (HNO3) and HF (4mL/10mL/2mL), followed by evaporation on a hotplate. The limits of detection (LOD) obtained using the optimised microwave protocol and ICP-MS measurements were below 0.1g/kg for the trace elements and below 0.2mg/kg for major elements.

Item Details

Item Type:Refereed Article
Keywords:microwave digestion, ICP-MS, carbonate-rich sediment, fluoride precipitate
Research Division:Earth Sciences
Research Group:Physical geography and environmental geoscience
Research Field:Palaeoclimatology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Durand, A (Mr Axel Durand)
UTAS Author:Chase, Z (Professor Zanna Chase)
UTAS Author:Townsend, AT (Associate Professor Ashley Townsend)
UTAS Author:Noble, T (Dr Taryn Noble)
UTAS Author:Panietz, E (Miss Emily Panietz)
UTAS Author:Goemann, K (Dr Karsten Goemann)
ID Code:109037
Year Published:2016
Funding Support:Australian Research Council (FT120100759)
Web of Science® Times Cited:6
Deposited By:Ecology and Biodiversity
Deposited On:2016-05-18
Last Modified:2018-04-11

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