Materials and methods
2.1. Farm selection and sampling
The study was carried out from September 2012 to August 2013.Unit for the statistical analysis was the raw bovine milk samples collected from cooling tanks from different dairy farms (n ¼ 40) located in the Argentina's central dairy region (Santa Fe Province). This area has heterogeneous soils generally suitable for agriculture with medium and high productive capacity. The principal activity is the livestock, mainly dairy based on alfalfa pastures. This area produces 37% of the country's total milk. In this region there are 2894 dairy farms (Ministerio de la Produccion, 2010). Sampling took place during four climatic seasons: spring-summer (2012) and autumn-winter (2013); and milk samples were immediately frozen (18 C) for further analysis. Milk from one specific farm was employed as blank sample for method development experiments, after checking the absence of AFM1 through IAC-UHPLC-MS/MS analysis.