G. O. Noonan, T. H. Begley, G. W. Diachenko, CFSAN, FDA, College Park, MD
Monofluoroacetic acid (MFA) , also referred to as compound 1080 is a rodenticide commonly used in the US and New Zealand and a naturally occurring toxic component of poisonous plants found in Australia, South Africa, and India. The availability, stability and proximity of MFA to agricultural products could potentially lead to an accidental or intentional contamination of food. Therefore a screening and confirmatory method for the detection of MFA in foods was needed. The screening method developed, utilized rapid sample cleanup and liquid chromatography mass spectrometry for detection. This method showed a high degree of specificity, with limits of detection (LOD) of 4 ppb and limits of quantitation (LOQ) of 13 ppb. Spike recoveries were matrix dependent and varied from 81 to 110% with comparable recoveries at low (2 ppm) and high (20 ppm) spiking levels. Reproducibility tests at the low spiking levels, had RSD's of less than 5% for all matrices analyzed. None of the unfortified samples showed detectable levels of MFA.
The qualitative confirmatory method developed is conceptually different from the screening method, ensuring that both methods would not be subject to the same interferences. The method uses the formation of the hydrazide of MFA through derivatization with 2-nitrophenylhydrazine. This derivatization is well established for the detection of carboxylic acids, but this is the first application to the detection of MFA. The derivatization yield was matrix dependent, however the LOD (<1 ppb) was sufficiently sensitive to confirm the presence of MFA in all spiked matrices. Reproducibility tests at the low spiking levels, had RSD's of approximately 6% for all matrices analyzed.