A Universal Method for Quantifying Elemental Sulfur and Selenium in Biological Matrices

Sulfur is a fundamental element in biology, influencing the origin of life, its evolution, and contemporary cellular processes. Yet, the study of elemental sulfur in biological systems remains constrained by the absence of accessible and robust quantification methods. We recently demonstrated that ‘ Reactive Sulfur Species ’ (RSS)—including “sulfane” sulfur forms such as polysulfides and elemental sulfur (S ₈ )—react with phosphines to yield phosphine sulfides. Here, we present a selective and reproducible method for quantifying S ₈ in biological matrices. S ₈ was isolated from biological samples via organic solvent extraction and confirmed by Raman spectroscopy. The extracted S ₈ is then reacted with triphenylphosphine (TPP) to form triphenylphosphine sulfide (TPP=S), which is quantified using ³¹ P nuclear magnetic resonance (NMR). Similarly, elemental selenium is quantified in biological samples using this methodology. These approaches yield high recovery and reproducibility across diverse biological samples, including mammalian and plant tissues and bacterial cultures. By enabling universal detection and quantification of elemental sulfur and selenium, this method opens new avenues for investigating chalcogenide-based redox biology.