ELISA determination of Aflatoxin M ₁ in milk and dairy products in Pakistan

A highly sensitive competitive ELISA was standardized to determine aflatoxin M1 (AFM1) in milk and dairy samples randomly collected from Faisalabad city, using Riedel-de-Haen, Aflatoxin M1 ELISA Systems, (Art–No. 45169). Standards of 5, 10, 25, 50, and 100 ng L−1 AFM1 in sample/standard buffer were used in optimizing anti-AFM1 antibodies and peroxidase–AFM1 conjugate. Linear standard curve showed increase in concentration (log C) accompanied by decrease in maximal absorbance (%B/B0) values (%B/B0 = 124.3 − 45.0 log C) with highly significant negative correlation (−0.973). The middle of the test (50% B/B0) was at 30 ng L−1 with 6.7 ng L−1 the lowest detection limit (90% B/B0). Duplicate analysis of 41 samples showed AFM1 levels below EC permissible limits (50 ng L−1) with maximums of 40, 13, and 7.4 ng L−1 in milk, yogurt and butter, respectively. However, possibility of exceeding limits cannot be excluded, and demands regular monitoring.