Affinity Column Cleanup and Direct Fluorescence Measurement of Aflatoxin M₁ in Raw Milk

Aflatoxin M₁ is a carcinogen secreted in the milk of cows which ingest feed contaminated with aflatoxin B₁ Surveillance of aflatoxin residues requires a simple, rapid, sensitive, and quantitative test. A test has been developed which uses an antibody affinity column to isolate aflatoxin M₁ from raw milk. The skim portion is passed directly through the column. The column is then washed and the aflatoxin M₁ eluted into a test tube. The affinity column provides sufficient sample cleanup to measure the aflatoxin level directly using a fluorometer. Using raw milk samples spiked with known amounts of aflatoxin M₁, the method provides 97% recovery over the range 0.05ppb to 0.5ppb. The detection limit is 0.05ppb. Values obtained on the fluorometer agree with those obtained by HPLC. The time required to quantitate a prepared sample is about 8 minutes.