Development of a diphasic dialysis method for the extraction/purification of residues of ethinylestradiol in hair of cattle, and determination by gas chromatography–tandem mass spectrometry

A confirmatory method for the analysis of ethinylestradiol extracted from cattle hair was developed. After the extraction of the xenobiotic from the hair, by using alkaline digestion, the purification of the extract was carried out by employing diphasic dialysis. For the optimization of the technique several parameters was evaluated such as pH, extraction solvents, temperatures, times and agitation speeds. The detection and confirmation of the steroid was accomplished by using a GC–MS2 ion trap system after trimethylsilylation. The calibration curve was linear over the range of 4–20 ng/g. The detection and quantification limit were 0.52 and 0.80 ng/g respectively; with recoveries up to 94%.