Challenges on Production of a Certified Reference Material of Ochratoxin A in Roasted Coffee: A Brazilian Experience.

Coffee is an important agricultural commodity with technical barriers for exportation because of possible contamination with ochratoxin A (OTA), a mycotoxin nephrotoxic and carcinogenic. The maximum limit for OTA in roasted coffee is 5.0 μg/kg in the European Union and 10 μg/kg in Brazil, and the use of certified reference materials (CRM) is required for reliable measurements. This paper describes the development of a candidate CRM of OTA in roasted coffee following the requirements of ISO 17034 and ISO Guide 35. A primary method of isotope dilution MS was developed and validated using (C)-OTA as internal standard. The sample preparation was based on AOAC using immunoaffinity column. The linear working range is 2.0-15.0 μg/kg, with recoveries of 92.2-110.8% and relative SDs lower than 12.4%. The method was successfully applied to the feasibility study, which defined the procedure for preparation of a large batch around 5 μg/kg. It was produced by spiking blank roasted coffee with OTA standard, mixing and filling in amber flasks with 50 g of coffee, and storing at -80°C. The homogeneity study showed an acceptable degree of heterogeneity of 1.44%, and the short-term-stability study defined the conditions for transportation as maximum temperature of 50°C up to 28 days. These results show that certification is possible. The long-term stability study at -20°C is in progress, and the characterization will be conduzed by a interlaboratory comparison. This material will be an important tool for QC in laboratories.