Selenium in Agricultural Products: Advances in Detection of Total Content and Speciation

Selenium (Se) is an essential trace element for humans, primarily obtained from dietary sources, particularly protein-rich foods. Owing to its narrow margin between nutritional requirement and toxicity, as well as the strong dependence of its bioavailability on chemical speciation rather than total concentration, accurate determination of Se in processed agricultural products is critically important. Organic Se species generally exhibit higher bioavailability, greater nutritional value, and lower toxicity compared to inorganic forms, highlighting the necessity of both total Se quantification and speciation analysis. This review critically evaluates recent advances in analytical methods for total Se determination and speciation, with emphasis on sample preparation, species stability, and factors affecting accuracy. While significant progress has been made in total Se analysis, speciation remains challenging due to low analyte levels, complex food matrices, species transformation during extraction, and the lack of standardized methods and certified reference materials. Consequently, combining total and speciation data is necessary for meaningful nutritional evaluation. Future work should focus on improving extraction protocols, enhancing the sensitivity of techniques such as HPLC-ICP-MS, and developing standardized methods for routine application in the food industry.