Identification of ractopamine residues in tissue and urine samples at ultra-trace level using liquid chromatography-positive electrospray tandem mass spectrometry.

Beta-agonist compounds are widely used in human therapeutics because of bronchodilator or heart tonic properties; they are also used as growth promoters in food-producing animals. Ractopamine is a forbidden molecule in the EU, but is registered as an additive in other countries such as in the USA for pigs. Consequently, efficient analytical methods were developed to survey residues in edible tissue and urine samples. This paper describes a protocol based on a powerful extraction and purification process and a liquid chromatography-positive electrospray mass spectrometry identification method. A validation was performed according to the "DG SANCO 1805/2000" European decision. The obtained decision limit (CCalpha) and detection capability (CCbeta) were as low as 10 and 30 ng/kg (ppt), respectively. This method appeared very efficient on incurred samples, including porcine edible tissues (meat, liver, kidney), tissues enriched in beta-agonist receptors (lung, retina), and finally bovine urine samples.