Application of electrospray ionisation mass spectrometry to the study of dilute aqueous oligomeric anions and their reactions

For the first time, electrospray ionisation mass spectrometry has been carried out on purely aqueous solutions of anions, specifically dilute (10(-3) mol dm(-3) isopolytungstates, peroxotungstates and heteropolymolybdates and tungstates. Many new species have been detected that have not previously been reported in water, including [W6O19](2-) and [W2O7](2-). To demonstrate its investigative potential, the method was used to identify the complex and previously uncharacterised reaction products from the reaction of H2O2 on powdered tungsten metal, where hexametalates form with up to four peroxo ligands, and also to track kinetic processes such as the course of metal-ion exchange between phosphododecametalates, and the attack of H2O2 on paratungstate B.