A study from a multi-institutional research team comprised of Wuchang University of Technology, Zhejiang University, University of Veterinary and Animal Sciences in Lahore, University of Szeged, Ghent University, and King Fahd University of Petroleum and Minerals personnel reviewed how ion chromatography (IC) can be used to analyze halogens and similar substances within inorganic matrices. Their findings were published in the Journal of Chromatography A (1).
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Inorganic matrices, such as metal concentrates, cement, and ores, play pivotal roles in infrastructure development, transportation, and energy. Non-metallic elements in these matrices, especially halogens, can influence quality, processing costs, and dynamics within their environment.
Halogens (fluorine, chlorine, bromine, iodine, and astatine) are five naturally occurring non-metallic elements whose compounds often form salts. With the exception of bromine and astatine, halogens are essential non-metallic elements for humans, animals, and plants; however, in both their elemental states and in most compound forms, these substances are often toxic. Legislation has been enacted in various countries to monitor halogen levels in different substances, although there remains room for further development in these efforts.
In this review article, various sample preparation methods were compared in conjunction with the benefits and costs of advanced techniques for detecting non-metals in complex matrices, with a particular focus on IC. Conventional analytical techniques have proven themselves costly, complex, and limited in efficiently determining pollutants in complex inorganic matrices for various reasons. IC has been viewed as an effective alternative, offering enhanced sensitivity, selectivity, cost-effectiveness, and the capability to simultaneously separate and quantify multiple types of analytes in complex matrices, making it widely used in environmental analysis for quantitatively assessing halogens and hazardous non-metallic elements. If IC is hyphenated with mass detection, such as conductivity detection (CD) or mass spectrometry (MS), or fluorescence/UV detectors, its detection capabilities are enhanced, making it effective for halogen determination. IC automation makes the technique user-friendly and suitable for addressing challenges in determining environmental pollutants in complex digests.
The primary challenge with this field is sample preparation, which poses risks of halogen losses and contamination. Wet digestion methods with inorganic acids are effective for decomposing many matrices and require additional care for determining halogens. As such, combustion methods in closed systems are preferred for improving limits of detection (LODs) and utilizing dilute solutions compatible with various detection techniques. Microwave-induced combustion (MIC), which involves combining combustion and acid digestion into a single closed-vessel, is believed to offer better efficiency and recovery for digesting difficult matrices in both open and closed systems (2). Further, steam distillation (SD) is claimed as a high-throughput and efficient alternative for clean digestion of multiple inorganic sample matrices, particularly for volatile analytes such as halogens. Its compatibility with IC only makes it more attractive for pollutant determination.
Despite the inherent challenges involved with determining halogens, its importance and growth cannot be highlighted enough. Instrumentation for halogen detection has improved, but there is still progress to be made with sample preparation methods and detection techniques; namely, throughput, LODs, and environmental considerations. Overall, IC plays a crucial role in quantitatively analyzing halogens and hazardous non-metallic elements in inorganic matrices for environmental monitoring and control.
(1) Muhammad, N.; Hussain, I.; Ali, A.; et al. Ion Chromatography: A Comprehensive Review of Sample Preparation Methods for Analysis of Halogens and Allied Nonmetals in Critically Challenging Inorganic Matrices. J. Chromatogr. A 2024, 1734, 465311. DOI: 10.1016/j.chroma.2024.465311
(2) Microwave-Induced Combustion for ICP-MS: A Generic Approach to Trace Elemental Analyses of Pharmaceutical Products. Spectroscopy 2011, 26 (4). https://www.spectroscopyonline.com/view/microwave-induced-combustion-icp-ms-generic-approach-trace-elemental-analyses-pharmaceutical-product (accessed 2025-1-31)
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