Effect of Spiking Contact Times on the Analytical Recovery of Aflatoxins

Aflatoxins are toxic secondary metabolites of fungi, mainly Aspergillus flavus and Aspergillus parasiticus the most common of which are aflatoxins B1, B2, G1 and G2, and M1 in milk. Aflatoxin B1 is normally predominant. The determination of aflatoxins, by extraction, immunoaffinity clean up and liquid chromatography with fluorescence detection is common practice. Recovery correction of the results obtained is mandatory in official analysis for which the only practical approach is separate determination of the analyte added either to aliquots of the sample or matrix blanks, a process commonly referred to as “spiking”. Variations in the spiking contact times before extraction could have an effect on the recovery of aflatoxins from the matrix. Herein we describe two studies, a short term (0.5 – 65 hours) and a long term (1 hr – 8 weeks) investigation of the effect of contact time on spike recovery in peanuts, figs and chilli powder. Generally it was found that recovery is dependent upon contact time and this effect is statistically significant for short contact times (less than 24 hours) while thereafter the recovery stabilises. The results from both studies indicated a small effect on contact times in some matrix/aflatoxin/storage condition combinations, however any effect is statistically insignificant compared to the method uncertainty.