Abstract
This work aimed to assess the efficiency of a portable total mercury (Hg) analyzer (Lumex RA-915 +) that employs direct thermal decomposition atomic absorption spectrometry (AAS) to liberate Hg from a sample matrix as well as validate the quantification method of total Hg in different materials that are used in cement production. Regarding the solid matrix of the samples, the approaches included matrix-matched certified reference materials (CRM) calibration and adding a standard calibration solution to the solid samples. While both calibration approaches were suitable for the instrumentation employed, the uncertainty of the Hg mass fraction in a CRM and the need to include several matrix CRMs that differed in analyte content added to the complexity of the case. Spiked calibration is an acceptable alternative to calibration because it provides a lower expanded uncertainty at 15 %, 15.5 %, and 21.7 %, for the highest (> 200 ng), middle (50–150 ng), and lowest (< 50 ng) concentration ranges, respectively, compared to matrix CRM calibration. The obtained expanded uncertainty, the minimal requirements for sample preparation, easy and straightforward calibration and measurement, and high sample output indicate that the quantification of total Hg with thermal decomposition coupled with AAS is suitable for materials that are used in cement production.
Highlights
Among many analytical methods that are used for Hg measurements in environmental samples, those that employ direct thermal decomposition as a means of extracting Hg from a sample matrix with atomic absorption spectrometry detection (AAS) have the benefits of utilizing either few or none of the reagents, minimal requirements for sample preparation, fast analysis, and minimal analyte loss [5–8]
A substitute approach was to add calibration solutions to the matrix of the samples (“spiked calibration” hereafter). This approach could be a suitable alternative because, during calibration, we were including the matrix of the considered sample, and the uncertainty of the calibration solution is much smaller compared to the matrix-matched certified reference materials (CRM)
Despite the suggestion that matrix CRMs are intended for quality control and validation studies, many publications describe the use of CRMs for calibration purposes [14, 17, 25]
Summary
Mercury (Hg) is recognized as a global pollutant with a complex biogeochemical cycle, which has toxic effects on human health. In addition to natural sources of Hg that form background environmental levels, anthropogenic activities that are associated with the combustion of fossil fuels have increased the mobilization of Hg in the environment [3]. Among many analytical methods that are used for Hg measurements in environmental samples, those that employ direct thermal decomposition as a means of extracting Hg from a sample matrix with atomic absorption spectrometry detection (AAS) have the benefits of utilizing either few or none of the reagents, minimal requirements for sample preparation, fast analysis, and minimal analyte loss [5–8]. Quantitative analysis in spectrometric techniques produces results whose accuracy depends on the instruments’ calibration to ensure comparability over time and among laboratories [9]. In most analytical techniques that are used for total Hg quantification, the calibration is performed with standards that are in an aqueous solution [11–13]. For total Hg quantification by thermal decomposition methods, where
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