High-performance liquid chromatographic/ion-trap mass spectrometric speciation of aquatic mercury as its pyrrolidinedithiocarbamate complexes

Mercury-pyrrolidinedithiocarbamate complexes are first time used for speciation of aquatic mercury with high-performance liquid chromatographic/ion trap-mass spectrometric method utilizing atmospheric pressure chemical ionization (APCI). The separation of the four mercury species was achieved in less than 5 min with a linear gradient profile of aqueous methanol from 70 up to 100% (v/v) in 4th min, isocratic elution at 100% up to 5th min and followed by a negative gradient to 70% in 6th min. The best separation was achieved on a reverse phase Zorbax Eclipse XDB C18 column (50 mm × 2.1 mm i.d., 1.8 μm particle size). The on-column limits of detection (injection volume 1 μL) were 370 pg for methylmercury (MeHg⁺), 280 pg for ethylmercury (EtHg⁺), 250 pg for phenylmercury (PhHg⁺) and 90 pg for inorganic mercury (Hg²⁺) when the data were collected in selective ion monitoring (SIM) mode. A method of isolation and preconcentration of the mercury species using a “home-made” C18 solid phase extraction (SPE) microcolumns was developed to enhance sensitivity of the method. The preconcentration factor as much as 2500 was achieved with on-column complex formation of mercury-pyrrolidinedithiocarbamate. Methanol (100%) was chosen for elution of preconcentrated mercury species. The method was applied for the determination of mercury species in river water samples.