Rapid simultaneous multielemental speciation by capillary electrophoresis coupled to inductively coupled plasma time-of-flight mass spectrometry

Rapid simultaneous multielemental speciation was carried out by combining c apillary electrophoresis (CE) with inductively coupled plasma time-of-fligh t mass spectrometry (ICP-TOFMS). Fast electrophoretic separation of a mixtu re of several anionic species and negative-charged metal-cyanide complexes was achieved by using a linear polyacrylamide-coated capillary. The separat ion of three arsenic species and two cobalt-cyanide complexes required less than 70 s in the presence of other anions and metal cyanides of Cu-II, Cr- VI, Ni-II and V-V. Simultaneous element-selective detection was provided by ICP-TOFMS. This method can acquire spectra at 20 kHz, a rate fast enough f or even the narrow transient peaks generated by CE. In this case, because t he CE peaks exhibited a 1-3 s full width at half maximum (FWHM), an integra tion time of 250 ms was employed. Thus, each single point in a transient pe ak results from the average of 5000 mass spectra. Furthermore, the multiele mental capability of the ICP-TOFMS enabled mass spectral separation of seve ral metal species that were not electrophoretically resolved. The effect of electric field strength, buffer concentration and applied hydrodynamic pre ssure at the head of the capillary on migration times and resolution has be en examined. Absolute detection limits for the different metal species were 1-20 pg for 20 nL injected sample volumes. Peak-area and elution-time repr oducibility were typically better than 4% RSD and 1% RSD, respectively, for 10 successive injections.