Analytical Procedures for the Determination of Aflatoxin B1 in Eggs of Laying Hens Using Immunoaffinity Columns and Liquid Chromatography with Post-Column Derivatisation and Fluorescence Detection

An analytical procedure for the determination of aflatoxin B-1 in eggs was introduced and validated in laboratory 1. The method consisted of the extraction of aflatoxin B-1 from a sample, purification of the extract with solvents, immunoaffinity column cleanup and the determination by liquid chromatography with post-column bromination and fluorescence detection at lambda (ex) = 362 nm and lambda (em) = 425 nm. The method was transferred to laboratory 2, where it was modified and validated. The limit of detection (LOD) and limit of quantification (LOQ) obtained in laboratory 1 were 2 and 6 ng/kg, respectively, and 2 and 5 ng/kg in laboratory 2, respectively. The repeatability of measurements in laboratory 1, represented by differences between results of duplicate measurements, was 10 ng/kg at the contamination level of 50 ng/kg. At the same concentration level, the standard deviation (s (R)) and the relative standard deviation (RSD (R)) for the within-laboratory reproducibility were 5.5 ng/kg and 11 %, respectively, and the measurement uncertainty was +/- 10 ng/kg. The mean recovery was 70 %. In laboratory 2, the repeatability of measurements at the contamination level of 20 ng/kg, represented by the standard deviation (s (R)), repeatability (r) and relative standard deviation (RSD (R)) was 4 ng/kg, 11 ng/kg and 20 %, respectively, and the recovery was 67 %. The results indicate that the procedures are suitable for the determination of aflatoxin B-1 in eggs and can be implemented for the routine analysis. Using the procedure validated in laboratory 1, 25 samples from farms in Slovenia were analysed. In none of the analysed samples, aflatoxin B-1 was detected.