Determination of Cl, Br, and I in Geological Materials by Sector Field Inductively Coupled Plasma Mass Spectrometry

Abstract

In this study, a simple and effective method for the simultaneous analysis of Cl, Br, and I in geological materials based on NH4HF2 digestion in open vessels (Savillex Teflon vials) is proposed. It is very interesting to note that Cl, Br, and I are not lost during NH4HF2 digestion at temperatures of 200–240 °C for 0.5–12 h in open vessels. This should be related to the alkaline atmosphere environment caused by the NH3 produced during NH4HF2 digestion, which suppresses the volatilization loss of Cl, Br, and I. A 100 mg sample of geological materials can be completely digested by using 400 mg of NH4HF2 at 220 °C for 2 h in Savillex Teflon vials. The use of new Savillex Teflon vials significantly reduced the procedural blanks of halogens compared with the old Savillex Teflon vials. The developed method was successfully applied to the simultaneous determination of Cl, Br, and I in a series of international geological reference materials. Most of the results were found to be in reasonable agreement with values reported in the literature. This simple, rapid, effective, and economical analytical method will significantly promote the development of halogen geochemistry.

Simultaneous Determination of Fluorine and Chlorine in Marine and Stream Sediment by Ion Chromatography Combined with Alkaline Digestion in a Bomb

“…The present method consumes a small amount of alkaline (0.75 mL 6% NaOH can extract fluorine and chlorine from 40 mg sample completely) and decreases the matrix effects in comparison to the alkaline fusion method, which requires a large amount of flux and the matrix separation step leading to a high procedural blank [5,28,30]. The NH 4 HF 2 digestion method has been proposed recently, which suppresses the volatilization loss of chlorine effectively owing to the formed ammonium salts with high boiling points, however, this method cannot determine fluorine and chlorine simultaneously [37]. In addition, compared to the complicated pyrohydrolysis, alkaline fusion and combustion methods [5,6,17,[28][29][30][31][32]35], the rapid alkaline digestion method is simple and can deal with a large batch of samples.…”

“…Although acid digestion has been commonly used for the decomposition of geological samples [38], mineral acids should be avoided to prevent losses of volatile halogens [37]. Alkaline fusion with NaOH can quantitatively extract fluorine [17] and chlorine [20][21][22] from geological materials, and the high-pressure digestion bomb requires a small amount of reagent, therefore NaOH was used as the digestion reagent.…”

“…So far, only a few methods have been used to extract fluorine and chlorine from geological samples, including pyrohydrolysis [5,6,29,31,32], alkaline fusion [5,17,28,30], microwave digestion [36], combustion [35] and NH 4 HF 2 digestion with subsequent ammonium dilution [37]. However, the pyrohydrolysis method is not suitable for the analysis of a large batch of samples [37]; alkali fusion requires a high flux-to-sample ratio which results in high blank levels, total dissolved solids (TDS) content and matrix effects [5,28], microwave digestion has poor recoveries caused by incomplete digestion of sediment samples containing zircon or other refractory minerals [38], and the NH 4 HF 2 digestion method cannot extract fluorine from geological materials [37]. Recently, a high-pressure digestion technique has been generally applied [8,36,[39][40][41].…”

Heavy halogen compositions of lamprophyres derived from metasomatized lithospheric mantle beneath eastern North China Craton

“…Bulk-rock halogen concentrations were determined by a rapid and efficient method developed for geological rock samples (He et al, 2019). This method uses ammonium hydrogen fluoride (NH 4 HF 2 ) to digest rock powder at 230°C for 2 hours.…”

“…This method uses ammonium hydrogen fluoride (NH 4 HF 2 ) to digest rock powder at 230°C for 2 hours. The NH 4 HF 2 reagent efficiently decomposes silicate samples and also avoids the possible volatile loss of halogens via the formation of ammonium halide during sample digestion (He et al, 2019). Aliquots of 10 μg L -1 Te were added to the sample supernatant solution as the internal standard.…”