Glutathione is a natural tripeptide (γ-L-glutamyl-L-cysteinylglycine) which participates in several physiological processes such as DNA synthesis, protein synthesis, cell membrane stabilization, amino acid transportation and xenobiotic detoxification. Glutathione exists in reduced form (GSH) and in oxidized form as disulfide (GSSG). The GSH/GSSG ratio is often used as a marker of the cellular redox state. GSH is a critical indicator protecting organisms against diseases and toxicities. Thus, measurements of GSH concentrations in biological samples are of importance, owing to its potential for disease diagnosis and providing valuable information for the understanding of GSH homeostasis.