Ochratoxin A is a mycotoxin produced by Penicillium and Aspergillus species. It is reported to be a genotoxic carcinogen. Ochratoxin A has been shown to occur in various cereals and can transfer from feed to edible animal products, particularly pig kidneys. Reliable analytical procedures for the determination of this nephrotoxin are essential for establishment and enforcement of tolerance levels. Certified reference materials play a vital part in the development and use of such analytical procedures.
The ultimate objectives of this project were to establish certified reference materials for ochratoxin A analysis in wheat; and to evaluate analytical procedures for its measurement in pig kidney materials through an intercomparison study involving a range of European laboratories.
The two wheat reference materials which were prepared as part of this project have been certified and are now available from JRC, IRMM, Geel, Belgium (Tel. +32 14 571 211; Fax +32 14 590 406). Values from nine of the laboratories participating in the certification exercise were accepted and the certified values determined to be:
CRM 471 <0.6 mg/kg ochratoxin A
CRM 472 8.2 mg/kg ochratoxin A with an uncertainty of +/-1.0 mg/kg
The first intercomparison study of ochratoxin A in pig kidney indicated problems with spiking of the freeze dried material, and extraction of ochratoxin A from this material. It was recommended that investigations into the most effective spiking regime and the most effective extraction solvents and techniques be carried out. A further project is now underway which will address these problems prior to carrying out a second intercomparison study of methods for the determination of ochratoxin A in pig kidney.
Two wheat reference materials were prepared, a "blank" and a "contaminated" material. The stability of these materials at -18°C and +4°C was demonstrated over a period of 24 months. The homogeneity of these materials was also established. Fifteen laboratories then participated in the certification exercise. Laboratories were chosen based on their method performance in the second intercomparison study, which had also been organised as part of this project.
Two freeze dried pig kidney materials were also prepared, a "blank" and a "contaminated" material. Again the stability of these materials was tested over a 6 month period, and homogeneity demonstrated. Twenty four European laboratories, including some with a particular interest in the analysis of meat and meat products, were invited to take part in the first intercomparsion study. Each laboratory was instructed to use their normal analytical procedure to determine ochratoxin A.