Comparison of two clean up techniques in isolation of ochratoxin A from red wine
Two procedures for the extraction of ochratoxin A (OTA) from red wine – the reference clean up procedure using specific immunoaffinity column (IAC), and solid phase extraction (SPE) in which an active carbon was employed, was compared. In SPE procedure, various mixtures of dichloromethane (D), toluene (T), acetonitrile (AC), methanol (M), and acetic acid (A) were used as OTA desorption agents. Two types of SPE carbonaceous columns were tested – commercial SPE columns (Supelclean<sup>TM</sup> Envi-Carb) with a nonporous graphitised carbon, and SPE columns prepared in our laboratory (further specified as Lab-Carb) that were filled with a micro particular granular carbon. OTA was extracted from spiked red wine by the use of both carbonaceous columns. The highest OTA mean recovery calculated in relation to the reference IAC procedure was 98.5%, using the Lab-Carb adsorbent and acetonitrile + toluene, 3 + 1 (v + v) as the elution mixture (OTA spike levels of 0.2 µg/l). Using the elution mixture of dichloromethane + methanol, 9 + 1 (v + v), the relative recoveries of 76.4% and 82.9% were reached at the OTA spike levels of 0.2 µg/l and 1.9 µg/l, respectively. The application of Envi-Carb adsorbent generally resulted in a very poor OTA recovery under the experimental conditions used (less than 50%). OTA was detected by liquid chromatography with fluorescence detection (LC-FLD) providing the detection limit of 0.011 µg/l and the quantification limit of 0.033 µg/l.
