Plasma-Based Techniques for Halogen Determination

Plasma-based analytical methods have become central to the accurate quantification of halogens—fluorine, chlorine, bromine and iodine—in diverse matrices. In these techniques, a high-temperature plasma serves both to atomise and excite sample constituents. The resulting atomic or ionic emission spectra can be recorded by optical emission spectrometry, while mass spectrometric approaches detect and quantify isotopic ions. Coupling plasma sources with efficient sample preparation strategies—such as pyrohydrolysis and microwave-induced combustion—enables the conversion of solid or complex organic materials into forms amenable to introduction into the plasma. Such combinations deliver limits of detection in the low microgram-per-gram to nanogram-per-gram range, broad dynamic ranges spanning several orders of magnitude, and high sample throughput. Applications span environmental monitoring of halogenated pollutants, quality control in pharmaceuticals and foodstuffs, and forensic or clinical analyses of trace halogen species. Innovations in microplasma devices and low-pressure systems are further reducing instrument footprints and power requirements, supporting field-deployable platforms. Ongoing developments aim at enhancing sensitivity, reducing interferences through novel reaction cells, and integrating automated calibration routines to deliver robust, real-time halogen speciation with minimal operator intervention.

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Research from all publishers

Recent work has demonstrated the effective use of pyrohydrolysis coupled to inductively coupled plasma mass spectrometry for the simultaneous determination of fluorine, bromine and iodine in mineral supplements. By optimising reactor temperature, carrier-gas flow and catalyst composition, researchers achieved quantification limits below one microgram per gram, with recoveries exceeding 95 % and sample frequencies of up to five per hour. This method offers a low-cost, routine approach for quality control laboratories.

Microwave-induced combustion combined with inductively coupled plasma optical emission spectrometry has been applied to the determination of bromine and chlorine in tobacco and other organic matrices. Closed-vessel combustion under oxygen at pressures up to 20 bar enables complete oxidation in under thirty seconds. Absorption of combustion products in dilute carbonate solutions yields detection limits in the single-digit microgram-per-gram range, inter-sample reproducibility better than 5 %, and capacity for simultaneous digestion of multiple samples.

A streamlined protocol for direct chlorine determination in glycerol-based polymers employs low-resolution inductively coupled plasma mass spectrometry without prior chemical decomposition. By diluting samples to 0.5 % matrix content and monitoring the 35Cl isotope, limits of detection of 3 µg g⁻¹ were attained. This approach minimises sample handling, reduces waste, and provides accuracy comparable to combustion ion-chromatography reference methods, making it attractive for rapid screening in industrial settings.

Plasma-Based Techniques for Halogen Determination publication trend

The graph below shows the total number of articles in plasma-based techniques for halogen determination across all publications each year (not limited to Nature Index journals).

Technical terms

Inductively coupled plasma (ICP): A high‐temperature, ionised gas sustained by radiofrequency energy, used to atomise and excite analytes.

ICP-OES (optical emission spectrometry): A detection method recording characteristic light emitted by excited atoms and ions in a plasma.

ICP-MS (mass spectrometry): A technique in which ions generated in the plasma are separated and quantified by their mass-to-charge ratio.

Pyrohydrolysis: A sample preparation process in which combustion in the presence of water vapour releases halogens as volatile species for trapping.

Microwave-induced combustion (MIC): A rapid digestion technique using microwave energy and oxygen to oxidise samples completely in sealed vessels.

References

1. Determination of bromine, fluorine and iodine in mineral supplements using pyrohydrolysis for sample preparation. Journal of the Brazilian Chemical Society (2012).
2. Bromine and chlorine determination in cigarette tobacco using microwave-induced combustion and inductively coupled plasma optical emission spectrometry. Journal of the Brazilian Chemical Society (2011).
3. Fast and Simple Analytical Method for Direct Determination of Total Chlorine Content in Polyglycerol by ICP-MS. Molecules (2018).