Separation and stacking of iodine species from seafood using surfactant-coated multiwalled carbon nanotubes as a pseudo-stationary phase in capillary electrophoresis

This article describes an on-line technique for hydrodynamic injections of long sample plugs with simultaneous stacking of iodine species in capillary electrophoresis (CE) with diode array detection. Surfactant-coated multi-walled carbon nanotubes (SC-MWNTs) were used as a pseudo stationary phase for the separation of iodate, tetraiodothyronine,triiodothyronine, diiodothyronine, and diiodotyrosine. The effects of MWNTs, concentration of SC-MWNTs and salt, of buffer pH value, injection times were examined. Under the optimized conditions, i.e. detection at 230 nm, a separation voltage 25 kV, a borate running buffer of pH 7.5 and a SC-MWNT concentration of 9 μg · mL⁻¹, the method gave relative standard deviations of the retention times and peak areas in intra-day assays (for n = 6) and for inter-day assays (for n = 3) of less than 4.49 and 5.80 %, respectively. The CE method was then applied to the analysis of the above iodine species in (spiked) kelp (kunbu) and porphyra, and recoveries ranged from 81.6 to 98.4 % with RSDs (n = 3) for extraction repeatability of <3.39 % in all cases. (author)