2.2.3. Preparation of samples
The frozen samples were placed in a fridge overnight to thaw and prior to centrifugation they were warmed for a few minutes in a water bath at 37 C and homogenized by occasionally gently inverting the containers by hand. Homogenized milk was transferred to suitable tubes and centrifuged for 15 min at 3500 rpm. Skimmed milk was carefully taken from the middle part of the tubes with a syringe and needle, and then filtered through filter paper under vacuum. For recovery studies defatted milk was spiked with AFM1 working standard solution to yield analyte concentrations 0.05 and 0.1 mg L1. The spiked milk was gently stirred for 2 h to allow appropriate contact between the added aflatoxin and the matrix.