During the early 1990s the marine dinoflagellate Alexandrium ostenfeldii was found to be producing a novel group of toxins called spirolides. Toxicity studies on mice showed that they are the causatives of PSP-symptoms like cramps and paralysis, presumably by blocking the excitation current in muscle and nerve cells. Structurally, spirolides are macrocyclic compounds particularly characterised by a tricyclic ether system and a seven-membered cyclic imine moiety. In recent LC-MS/MS investigations of the AOSH2 strain originating from Ship Harbour (Canada) we found structurally yet unknown spirolides. Precursor scans of characteristic fragment-ions revealed molecular ion masses not corresponding to already known structures or exhibiting different fragment ion spectra than spirolides of equal molecular weight. Since the unambiguous structural elucidation of these compounds requires nuclear magnetic resonance (NMR) spectroscopy, high sample amount in the upper microgram range and high purity of the isolates from raw cell extracts is needed. We used low pressure column chromatography and solid phase extraction (SPE) to remove major matrix compounds from the raw cell extracts. Finally we developed a LC-MS/MS method for the baseline separation of the complex spirolide mixture.