Dilutions of the mucoactive agents and Trolox, a water-soluble vitamin E analogue used as a standard, were prepared in Dulbecco’s phosphate-buffered saline (DPBS), previously sparged with nitrogen, and incubated with previously heated 0.23 mM 2,2'-azinobis-(-3 ethylbenzothiazoline-6-sulphonate)/2.3 mM 2,2'-azobis-(-2-amidinopropane).