Immunoaffinity column cleanup with liquid chromatography for determinationof aflatoxin M-1 in liquid milk: Collaborative study

A collaborative study was conducted to evaluate the effectiveness of an imm unoaffinity column cleanup liquid chromatographic method for determination of aflatoxin M-1 in milk at proposed European regulatory limits. The test p ortion of liquid milk was centrifuged, filtered, and applied to an immunoaf finity column. The column was washed with water, and aflatoxin was eluted w ith pure acetonitrile. Aflatoxin M-1 was separated by reversed-phase liquid chromatography (LC) with fluorescence detection. Frozen liquid milk sample s both naturally contaminated with aflatoxin M-1 and blank samples for spik ing, were sent to 12 collaborators in 12 different European countries. Test portions of samples were spiked at 0.05 ng aflatoxin M1 per mt. After remo val of 2 noncompliant sets of results, the mean recovery of aflatoxin M-1 w as 74%. Based on results for spiked samples (blind pairs at 1 level) and na turally contaminated samples (blind pairs at 3 levels) the relative standar d deviation for repeatability (RSDr) ranged from 8 to 18%. The relative sta ndard deviation for reproducibility (RSDR) ranged from 21 to 31%, The metho d showed acceptable within- and between-laboratory precision data for liqui d milk, as evidenced by HORRAT values at the low level of aflatoxin M-1 con tamination.