On-line hyphenation of flow injection, miniaturized capillary electrophoresis and atomic fluorescence spectrometry for high-throughput speciation analysis

A hyphenated technique was developed for high-throughput speciation analysis by on-line coupling of flow injection (FI), miniaturized capillary electrophoresis (CE) and atomic fluorescence spectrometry (AFS). Two interfaces were used to couple all three systems: the first to couple FI and CE and the second to couple miniaturized CE and AFS. The first interface was a modified flow through chamber, connected to the FI valve with a piece of PTFE tube (0.1 mm i.d. × 20 cm long). The capillary outlet was coupled to the AFS by using the second concentric “tube-in-tube” interface. Split sampling was achieved in the electrokinetic mode. Inorganic mercury (Hg(II)) and methylmercury (MeHg(I)) were taken as model analytes to demonstrate the performance of the developed hyphenated technique. A volatile species generation (VSG) technique was employed to convert the analytes from the CE effluent into their respective volatile species. Baseline separation of Hg(II) and MeHg(I) was achieved by CE in a 50 μm i.d. × 8 cm long capillary at 3.0 kV within 60 s. The precisions (RSD, n = 12) were in the range of 0.7–0.9% for migration time, 3.8–4.2% for peak area, and 2.1–3.5% for peak height. The detection limits were 0.1 and 0.2 μg mL−1 (as Hg) for Hg(II) and MeHg(I) with a sample throughput of 60 samples h−1. The recoveries of both mercury species in the water samples studied were in the range of 93–106%.