Guaiacol (Standard) is a reference standard for research and analysis in studies involving Guaiacol. Guaiacol (2-Methoxyphenol) is a precursor to various flavorants, such as eugenol and vanillin. Its derivatives are used medicinally as an expectorant, antiseptic, and local anesthetic. It also can be used as an indicator in chemical reactions that produce oxygen. When oxygen binds to it, the complex turns yellowish brown and absorbs light maximally at about 470 nm.