Speciation of mercury compounds by capillary electrophoresis coupled on-line with quadrupole and double-focusing inductively coupled plasma mass spectrometry

The development and analytical characterization of capillary electrophoresi s (CE) coupled on-line with both quadrupole (Q) and double focusing (DF) in ductively coupled plasma mass spectrometry (ICP-MS) for the separation and determination of three chemical species of Hg (CH3CH2Hg+, CH3Hg+ and Hg2+) are described. The Hg compounds are separated as mercury-cysteine complexes by capillary zone electrophoresis in a 100 cm x 75 mu m id fused silica ca pillary at 20 kV and using a 20 mM sodium tetraborate decahydrate buffer (p H = 9.3). At relatively high concentrations (parts per million level), the determination of these compounds can be carried out by means of UV detectio n. However, the determination of low mercury concentrations (parts per bill ion level) can be achieved only by coupling to ICP-MS detection. To accompl ish this coupling a conventional concentric nebulizer has been used. The op timization of the CE-ICP-MS interface operation parameters as well as sampl e stacking conditions of the analytes are discussed. The analytical perform ance characteristics of the developed CE-ICP-MS methodology have been evalu ated and limits of detection were 4 and 7 mu g l(-1) (as Hg) for inorganic mercury and methylmercury, respectively. Such low levels for this CE techni que are achieved via sample stacking and the use of DF-ICP-MS at low resolu tion for specific mercury detection.