Evaluation of methods for ochratoxin A determination in green and roasted coffees

Different extraction solvents and cleanup techniques for mycotoxins determination were evaluated for green and roasted coffee. Classical techniques such as partition and clarification as well as solid phase extraction (silica, octadecylsilyl, cianopropyl and immunoaffinity columns) were tested. Only immunoaffinity columns were capable to effectively remove interferents from coffee extracts allowing ochratoxin A to be determined by HPLC and fluorescence detection at levels of 0,7 ng/g. Two commercial brands of immunoaffinity columns were evaluated for ochratoxin A recovery and repeated use. Average recovery for one brand was 97% and was above 70% on the fourth use. Average recovery for a second brand was 73% on the first use and below 30% on the second use.