Ochratoxin A case study: Establish metrological traceability of mycotoxin measurements using certified reference materials

For the US Food and Drug Administration's (FDA) mycotoxin program, the desired application of certified reference materials (CRMs) is primarily for validating methods for the determination of mycotoxins in foods and establishing metrological traceability of measurement results generated by such validated methods. The latter has been an important but insufficiently addressed challenge due to the lack of appropriate protocols and CRMs. Taking advantage of two recently available mycotoxin CRMs, OTAN-1 and Standard Reference Material (SRM) 1565, a protocol was developed for systematically examining uncertainty and establishing metrological traceability of measurement results of ochratoxin A (OTA) in corn through a series of calibration operations using the two CRMs. Instrument and method calibrations were performed using OTAN-1 and SRM 1565. The OTA value and its standard and expanded (k = 2, approximately 95% confidence) uncertainties were estimated from the calibration data and documented. These results demonstrate that the major contributing source of uncertainty is the sample matrix, highlighting the important role of the certified matrix reference material in method calibration. The value of OTA (38.5 +/- 7.2 mu g/g; 95% confidence interval) in the incurred sample was metrologically traceable to the International System of Units through two CRMs using the multi-laboratory validated liquid chromatography-mass spectrometry FDA compendial method. In addition, an alternative estimation of uncertainty was conducted using a one-point calibration, resulting in comparable uncertainty.