Interlaboratory study for ochratoxin a determination in cocoa powder samples

This paper describes the interlaboratory study aimed at validating a HPLC method of analysis for the determination of ochratoxin A (OTA) in cocoa powder. The method was tested at three levels of OTA, covering the range in which presumably European regulatory limits could fall. OTA was extracted from samples by blending with aqueous solution of bicarbonate, diluting with a solution of phosphate buffer saline, filtering, and cleaning-up by an immunoaffinity column containing antibodies specific to OTA. After washing the immunoaffinity column, OTA was eluted with methanol, identified by reversed-phase HPLC, and quantified by fluorescence detection. Five coded materials (blank and naturally contaminated samples) were sent to 31 laboratories (25 national and six European), together with OTA calibrant and spiking solutions. From the provided results, the relative standard deviation for repeatability (15-31%) and reproducibility (29-40%) showed reliable results adequately matching with the criteria suggested by European Committee for Standardization (CEN) for the analysis of mycotoxins, as shown by HORRAT values for all three levels of contamination. This validated method makes it possible to detect OTA in cocoa powder at mug/kg levels, representing, therefore, a useful tool for the control of foodstuffs, in accordance with the upcoming communitary legislation.