Determination of roquefortine C in blue cheese using on-line column-switching liquid chromatography

A method is described for the determination of roquefortine C in (blue) che ese. After liquid-liquid extraction with a mixture of hydrochloric acid and methanol, and filtration, an aliquot is analysed using column-switching re versed-phase liquid chromatography. The recovery of roquefortine C in Fetta cheese is about 85%, the calibration curve is linear from 10 to 2500 ng g( -1) (r(2) = 0.998), and the detection limit is about 10 ng g(-1). In differ ent batches of Danish Blue concentrations of 1000-2000 ng g(-1) of roquefor tine C are found. As regards the stability of roquefortine C its half-life in diffuse daylight is ca. 50 min, while after irradiation with ultraviolet light, it is about 10 min. (C) 1998 Elsevier Science B.V. All rights reser ved.