Determination of aflatoxin B-1 in baby food (infant formula) by immunoaffinity column cleanup liquid chromatography with postcolumn bromination: Collaborative study

A collaborative study was conducted to evaluate the effectiveness of an imm unoaffinity column cleanup liquid chromatography (LC) method for determinat ion of aflatoxin B-1 in a milk powder based infant formula at a possible fu ture European regulatory limit (0.1 ng/g). The test portion was extracted w ith methanol-water (8 + 2 [v + v]), filtered, diluted with water, and appli ed to an immunoaffinity column. The column was washed with water to remove interfering compounds, and the purified aflatoxin B-1 was eluted with metha nol. The separation and determination of the aflatoxin B-1 was performed by reversed-phase LC and detected by fluorescence after postcolumn derivatiza tion (PCD) involving bromination. PCD was achieved with either pyridinum hy drobromide perbromide (PBPB) or an electrochemical (Kobra) cell by addition of bromide to the mobile phase. The baby food (infant formula) test sample s, both spiked and naturally contaminated with aflatoxin B-1, were sent to 14 laboratories in 13 different European countries. Test portions were spik ed at levels of 0.1 and 0.2 ng/g for aflatoxin B-1. Recoveries ranged from 101 to 92%. Based on results for spiked test samples (blind pairs at 2 leve ls) and naturally contaminated test samples (blind pairs at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 3.5 to 14% . The relative standard deviation for reproducibility (RSDR) ranged from 9 to 23%. Nine participants used PBPB derivatization, and 5 particpants used the Kobra cell. There was no evidence of method performance depending on th e derivatization method used. The method showed acceptable within- and betw een-laboratory precision for baby food matrix, as evidenced by HORRAT value s, at the target levels of determination for aflatoxin B-1.