Reagent for the high-performance liquid chromatography determination of peroxycarboxylic acids

The synthesis and application of a new thiomethoxy-functionalised azo compound for the determination of peroxycarboxylic acids is described. 2-[(3-{2-[4-Amino-2-(methylsulfanyl}phenyl]-1- diazenyl)phenyl)sulfonyl]-1-ethanol reacts selectively with peroxycarboxylic acids in the presence of a large excess of hydrogen peroxide to yield the corresponding sulfoxide. Sulfide and sulfoxide are separated easily using reversed phase HPLC. An important advantage of the new reagent is the absorption maximum of the sulfoxide at wavelengths higher than 400 nm. The cross selectivity towards colored matrix components in real samples is therefore minimised. The method is characterised by an applicable concentration range over more than two decades and low cross reactivity towards hydrogen peroxide and potassium persulfate. External calibration with the respective sulfoxide leads to accurate and reliable results.