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

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Abstract
Rapid simultaneous multielemental speciation was carried out by combining capillary electrophoresis (CE) with inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS). Fast electrophoretic separation of a mixture of several anionic species and negative-charged metal–cyanide complexes was achieved by using a linear polyacrylamide-coated capillary. The separation of three arsenic species and two cobalt–cyanide complexes required less than 70 s in the presence of other anions and metal cyanides of CuII, CrVI, NiII and VV. Simultaneous element-selective detection was provided by ICP-TOFMS. This method can acquire spectra at 20 kHz, a rate fast enough for even the narrow transient peaks generated by CE. In this case, because the CE peaks exhibited a 1–3 s full width at half maximum (FWHM), an integration time of 250 ms was employed. Thus, each single point in a transient peak results from the average of 5000 mass spectra. Furthermore, the multielemental capability of the ICP-TOFMS enabled mass spectral separation of several metal species that were not electrophoretically resolved. The effect of electric field strength, buffer concentration and applied hydrodynamic pressure at the head of the capillary on migration times and resolution has been examined. Absolute detection limits for the different metal species were 1–20 pg for 20 nL injected sample volumes. Peak-area and elution-time reproducibility were typically better than 4% RSD and 1% RSD, respectively, for 10 successive injections.