Post-column hydride generation with in-situ preconcentration in a dielectric barrier discharge atomizer for sensitive...

Significant differences in toxicity among arsenic species lead to an urgent need to develop novel strategies for As speciation analysis. Toxicologically relevant species include inorganic arsenic, monomethylarsonic acid, dimethylarsinic acid, and trimethylarsine oxide. A method based on high-performance liquid chromatography (HPLC), hydride generation (HG), and atomic absorption spectrometry (AAS) was developed as an alternative to the commonly used HPLC coupled with inductively coupled plasma mass spectrometry (ICP-MS).

Arsenic species eluting from a chromatographic column were converted to their volatile species using HG. Then, one by one, they were in-situ preconcentrated in a dielectric barrier discharge atomizer, which resulted in narrower peaks measured by AAS, thereby improving their limits of detection (LODs). Quantitative preconcentration was achieved by adding O₂ to a carrier gas (Ar), while their rapid release was achieved by interrupting its flow. A lab-made gas control unit ensured communication and perfect synchronization among the HPLC, an automated three-way valve for O₂ introduction, and the AAS instrument. A "hybrid" mode of determination was useful for expanding the working range for samples with a significant difference in concentrations of As species. Only species at low concentrations could be preconcentrated, while the others can be quantified in the same run without preconcentration. The proposed method applicability was validated using reference materials of human urine (SRM 2669) and marine tissue (DOLT-5).

The developed analytical procedure is fully automated, with a clear application potential, offering a great alternative method for As speciation analysis without ICP-MS while maintaining relatively low LODs.