A QuEChERS/LC-MS method for the analysis of ractopamine in pork

The development of rapid, high sample throughput methods is constantly demanded by food analytical laboratories. Several current methods for the analysis of ractopamine deal with time-consuming procedures or complicated sample pretreatment steps. Thus, this study aimed to validate and to optimize a simple method for the extraction of ractopamine from pork using a “Quick, Easy, Cheap, Effective, Rugged and Safe” (QuEChERS) approach. Extraction was carried out with an acetonitrile acidic solution and then sodium chloride was used to promote salting out, increasing the solubility of ractopamine. Anhydrous magnesium sulfate was added to remove water and the clean-up was carried out with C18 and primary/secondary amine. Ractopamine was then determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) within 4.5 min only, before a single extraction procedure. Full validation was performed in accordance to Commission Decision 2002/657/EC. Additionally, matrix effect, limit of detection (LoD), limit of quantitation (LoQ) and measurement uncertainty were also determined. Linear range was among 2.5-20 μg/kg. LoD and LoQ were set to 1.5 μg/kg and 2.5 μg/kg, respectively, being below the maximum residue limit established by most countries. A high throughput screening and confirmatory tool, combined with a cheap and fast sample pretreatment method was developed. The method proved to be reproducible and sensitive and its applicability was checked on several samples of pork and pork products, with results that ranged from below LoQ to 6.54 μg/kg.