Analysis for endogenous and recombinant porcine somatotropine in serum Original Research Article

The use of somatotropine for food/milk producing animals is allowed in several countries. The European Union however, has banned its use for these purposes. Consequently effective analytical methods are needed for residue control, which, until now, were not available. This paper describes studies into the use of liquid chromatography–mass spectrometry (LC–MS) for the detection and identification of somatotropine at residue levels in biological materials. It is demonstrated that it is possible to discriminate between endogenous and recombinant somatotropine, based on the difference in molecular mass caused by a difference in amino acid composition, at levels of 10 ng ml−1. Based on this principle two methods for the isolation of endogenous and recombinant porcine somatotropine from samples of serum were developed. One is based on diafiltration of serum and gel permeation chromatography (GPC), the second on a combination of immunoaffinity chromatography (IAC) and diafiltration. Analysis is performed with micro-LC–MS. The detection limit for both methods is approximately 10 ng ml−1 recombinant and endogenous porcine somatotropine in serum.