Determination of Thiomersal by Flow Injection coupled with Microwave-Assisted Photochemical Online Oxidative Decomposition of Organic Mercury and Cold Vapor Atomic Fluorescence Spectroscopy

We developed a flow injection (FI) method for the determination of thiomersal (sodium ethylmercurithiosalicylate, C9H9HgNaO2S) based on the UV/microwave (MW) photochemical, online oxidation of organic mercury, followed by cold vapor generation atomic fluorescence spectrometry (CVG-AFS) detection. Thiomersal was quantitatively converted in the MW/UV process to Hg(II), with a yield of 97 ± 3%. This reaction was followed by the reduction of Hg(II) to Hg(0) performed in a knitted reaction coil with NaBH4 solution, and AFS detection in an Ar/H2 miniaturized flame. The method was linear in the 0.01 - 2 ?g mL-1 range , with a LOD of 0.003 ?g mL-130 . This method has been applied to the determination of thiomersal in ophthalmic solutions, with recoveries ranging between 97 and 101 %. We found a mercury concentration in commercial ophthalmic solutions ranging between 7.5 and 59.0 ?g mL-1 .