Determination of aqueous methylmercury species using electrospray mass spectrometry

,4 new method for the determination of methylmercury using liquid chromatography coupled to electrospray ionization mass spectrometry (ESI/MS) was developed. Individual ESI parameters were optimized yielding a limit of detection for methylmercury of 39 ng/mL. ESI/MS-active methylmercury species in solution were identified and compared with species predicted by equilibrium distribution modeling. The ESI/MS technique was applied to determine the distribution of methylmercury species in aqueous solution as a function of pH. For the first time, we report on the mass spectrometric identification of polynuclear methylmercury species such as [(CH3Hg)(2)OH](+) and [(CH3Hg)(3)O](+).