Speciation of selenium through chromatography with atomic techniques

This review article provides an overview of selenium speciation using chromatographic and atomic techniques, based on a survey of relevant studies published in the 21st century. Selenium is an essential element, but the narrow range between deficiency and toxicity makes determining its various chemical forms in many samples fundamental. The total selenium content is insufficient to understand its behavior, as its various species exhibit distinct physicochemical and toxicological properties. In general, organic forms, such as selenomethionine (SeMet) and methylselenocysteine (MeSeCys), are less toxic and more bioavailable than inorganic species and are also associated with beneficial health effects, such as antioxidant activity and potential disease-prevention benefits. Therefore, selenium speciation analysis in various matrices is fundamental to understanding its toxicity, bioavailability, biotransformation, and bioaccumulation, since different chemical species exhibit distinct biological behaviors. Strategies combining chromatographic and atomic detection techniques have been explored for selenium speciation, leveraging separation resolution and detection sensitivity to achieve selective methods with low detection limits and applicability to complex matrices. The most used techniques for speciation include high-performance liquid chromatography (HPLC) and gas chromatography (GC), typically coupled to inductively coupled plasma mass spectrometry (ICP-MS) or other atomic detectors, such as atomic absorption spectroscopy (AAS) and atomic fluorescence spectroscopy (AFS). In addition to reviewing the literature on chromatography-atomic techniques combinations, sample preparation, separation methods, and detectors were discussed. Applications in food, biological, and environmental samples are presented, highlighting the importance of speciation for evaluating selenium toxicity and bioavailability. This review indicates that significant challenges remain due to low analyte concentrations, the risk of interconversion between species, and the emergence of new demands, such as analyzing complex matrices of food, supplements, and biological samples. This shows that Se speciation is a dynamic, continually evolving field essential to analytical chemistry and understanding the effects of selenium on health and the environment.