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.