An intercomparison of methods for the determination of ochratoxin A in pig kidney.

The preparation of two pig kidney materials is described, together with a report on the results of an intercomparison study of methods to determine ochratoxin A levels in these materials. The materials were prepared, and the intercomparison study carried out within the European Commission. Measurements and Testing Programme, which is the successor of the Community Bureau of Reference (BCR). The materials were prepared from blank and naturally-contaminated pig kidneys and were freeze-dried. Details are given on the freeze-drying and packaging procedure, and the checks to ensure homogeneity and stability of the freeze-dried materials. The intercomparison study involved 20 European laboratories, which analysed the naturally-contaminated (freeze-dried) sample (ochratoxin A content approximately 10 micrograms/ kg based on fresh weight) and the 'blank' sample (ochratoxin A content < 0.6 microgram/kg based on fresh weight) using a variety of procedures for extraction and clean-up. All laboratories used HPLC as the determinative step. Recoveries were found to range from 43 to 128%. The study highlighted problems with recovery of spiked ochratoxin A from freeze-dried pig kidney material. There is a clear need to improve analytical performance, particularly with respect to the extraction efficiency from this type of matrix.