Determination of the neuropeptides arginine vasotocin and isotocin in brains of three-spined sticklebacks (Gasterosteus aculeatus) by off-line solid phase extraction-liquid chromatography–electrospray tandem mass spectrometry

A method based on solid phase extraction (SPE) followed by liquid chromatography–electrospray ionisation tandem mass spectrometry for the determination of the nonapeptides arginine vasotocin (AVT) and isotocin (IT) in brains of three-spined sticklebacks (Gasterosteus aculeatus) is described. Separation and detection were optimized using synthetic standards. Limits of detection (LOD) for standard solutions were 160 pg mL−1 for AVT and 250 pg mL−1 for IT. The SPE procedure hardly affected the LODs for standard solutions. Mainly because of ion suppression, LODs for AVT and IT in brains were approximately 5 and 25 pg mg−1, respectively. The concentrations determined in the brain of several fishes ranged from 10 to 500 pg mg−1 for AVT and from 400 to 4000 pg mg−1 for IT.