Ochratoxin A in wheat: a second intercomparison of procedures

Area of Science:

• Food safety analysis
• Mycotoxin determination
• Analytical chemistry

Background:

• The European Commission's Measurements and Testing Programme (BCR) initiated a project to enhance ochratoxin A determination methods.
• A previous intercomparison focused on wheat with approximately 13 µg/kg ochratoxin A.

Purpose of the Study:

• To assess and compare various methodologies for ochratoxin A determination in naturally contaminated wheat.
• To evaluate the performance of different extraction, clean-up, and High-Performance Liquid Chromatography (HPLC) procedures.
• To investigate the impact of immunoaffinity column clean-up compared to conventional methods.

Main Methods:

• Twenty-six laboratories from 11 European countries participated.
• Samples included naturally contaminated wheat (approx. 7 µg/kg) and a blank wheat sample (< 0.2 µg/kg).
• Participants employed diverse extraction solvents and clean-up techniques, with HPLC as the primary detection method.

Main Results:

• Normal methods showed recoveries from 58% to 114%, with most within the 70-110% range.
• Immunoaffinity column recoveries varied (58-114% for one type, 4-86% for another).
• Between-laboratory coefficient of variation was 34% for normal methods and 34-42% for immunoaffinity columns.

Conclusions:

• Spiking protocols, particularly the evaporation time for spiking solvent, significantly impact recovery accuracy.
• Standardization of methods and careful attention to sample preparation are crucial for reliable ochratoxin A quantification.
• Further investigation into spiking procedures is recommended to improve inter-laboratory reproducibility.