ELISA determination of Aflatoxin M1 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.