Liquid Chromatographic Determination of Ochratoxin A in Coffee Beans and Coffee Products

Publisher Website
Google Scholar
Abstract
A liquid chromatographic method for the determination of ochratoxin A in coffee beans (green and roast), instant coffee, and coffee drink is described. The sample is subjected to extraction with methanol-1% aqueous sodium bicarbonate (1 + 1) and C18 cartridge cleanup. The extract is chromatographed on a Nucleosil 5C18 column with a mobile solvent of acetonitrile-water-0.2M phosphate buffer pH 7.5 (50 + 47 + 3) containing 3mM cetyltrimethylammonium bromide as an ionpair reagent. Ochratoxin A is detected with a fluoromcter (excitation 365 nm, emission 450 nm). The sensitivity was increased 20-fold by using ion-pair resolution. The detection limits corresponded to 2 μg/kg for coffee beans, 5 μg/kg for instant coffee, and 0.2 μg/kg for coffee drink. The recoveries from coffee products were generally better than 80.7% and the relative standard deviations were 3.43-5.93%. The peak coinciding with ochratoxin A can be confirmed by treatment using alcohol (methanol, ethanol, or n-propanol) and H2S04.