Liquid Chromatographic Simultaneous Determination of Peroxycarboxylic Acids Using Postcolumn Derivatization

The first liquid chromatographic method with postcolumn derivatization for the simultaneous determination of peroxycarboxylic acids is described. Aliphatic peracids with chain lengths from C2 to C12 are separated by HPLC on a reversed-phase C18 column with acetonitrile/water gradient elution. For improved peak shape, tetrahydrofuran and acetic acid are added to the aqueous eluent. After chromatographic separation, the peroxycarboxylic acids react with 2,2‘-azino-bis(3-ethylbenzothiazoline)-6-sulfonate, a popular substrate for the enzyme peroxidase. Iodide traces are added as catalyst. The oxidation product, a green radical cation, is determined using a UV/visible detector in four characteristic regions of the visible and near-infrared spectrum in the range 405−815 nm. The advantages of the new method are detection limits in the low micromolar range, negligible matrix interferences, high reproducibility, and the possibility for simultaneous determination of several peroxycarboxylic acids.