Determination of sterigmatocystin in cheese by high-performance liquid chromatography-tandem mass spectrometry

Different cheese samples produced in Latvia (eight) and Belgium (13) were analysed for their sterigmatocystin (STC) content. Only two (9.5%) of the samples were positive for STC with concentration levels of 1.23 and 0.52 microg kg(-1), respectively. Five (24%) samples contained STC above the limit of detection (0.03 microg kg(-1)) but below the limit of quantification (0.1 microg kg(-1)), A sensitive liquid chromatography-electrospray positive ionisation-tandem mass spectrometry (LC-MS/MS) method, which was previously developed for the analysis of STC in grains, was modified and applied to the analysis of STC in cheese. This method involved sample extraction with acetonitrile-water (90 : 10, v/v), defatting with n-hexane, solid-phase extraction, separation on a reversed-phase C(18) column, and STC detection by LC-MS/MS.