2016 journal article
Effects of HCl pretreatment, drying, and storage on the stable isotope ratios of soil and sediment samples
RAPID COMMUNICATIONS IN MASS SPECTROMETRY, 30(13), 1567–1575.
TL;DR:
A temperature-dependent change in the isotopic ratios of long-term stored samples was observed during this study; therefore, relatively short-term storage of freeze-dried samples is preferable and HCl pretreatment is not recommended for δ(15) N andδ(34) S analysis.
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UN Sustainable Development Goal Categories
14. Life Below Water
(Web of Science; OpenAlex)
Source: Web Of Science
Added: August 6, 2018
RationaleStable isotope (δ13C, δ15N, δ34S values) analysis has become increasingly important for tracing contaminant sources in environments. Pretreatment of environmental samples allows accurate analysis of stable isotope ratios. The pretreatment of a sample and its subsequent preservation could either contaminate or create experimental artifacts affecting the validity of the resulting C/N ratios and the elemental isotopic contents of a sample.MethodsThe effects of acid pretreatment (0.1, 0.5, 1, 2, 5, 13 M HCl) and exposure period (2, 6, 12, 24, and 48 h) on the stable isotopic ratios of marine sediment (MS), river sediment (RS) and terrestrial soil (TS) samples were evaluated. The effects of storage temperatures (–80, –20 and 2°C), storage duration (1 week, 1 to 12 months) and washing steps (1, 2, 3, 5, 7 or 12 times) on the stable isotopic ratios were also considered. The %C, %N and %S, as well as the δ13C, δ15N, and δ34S values, of each sample were measured using continuous flow Elemental Analyzer/Isotope Ratio Mass Spectrometry (EA/IRMS).ResultsThe HCl treatment was applicable for δ13C analysis. However, the acid concentration and duration of exposure that brought about total removal of carbonate for the three sample types varied; e.g. the TS sample required stronger acid and a shorter exposure time. Storage time also had an effect: the δ13C values were lower and the δ15N and δ34S values higher after storage for 300 days.ConclusionsHCl pretreatment effectively eliminates carbonates and thereby helps δ13C analysis of the organic fraction. HCl pretreatment is not recommended for δ15N and δ34S analysis. Freeze‐drying of samples is recommended rather than oven drying. A temperature‐dependent change in the isotopic ratios of long‐term stored samples was observed during this study; therefore, relatively short‐term storage (–80°C) of freeze‐dried samples is preferable. Copyright © 2016 John Wiley & Sons, Ltd.