Comparison of HPLC and micellar electrokinetic chromatography in determination of sulfonated azo dyes in waste water

Capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) are compared for the analytical separation of eight environmentally significant azo dyes, mono-, and di-sulfonated compounds. Optimum separation of these dyes by MEKC was achieved using a buffer of ammonium acetate 9.5 mM, Brij 35 0.1%, pH 9 and by applying electromigration injection at 12 kV for 30 s. Identification was made by the absorbance spectra of each peak. High-performance liquid chromatography separations were performed on a Discovery RP Amide C16 5 mum with a gradient from 25% to 50% acetonitrile and a buffer, made of 1 mug/L tetrabutylammonium bromide, 0.02% acetic acid and of 50 mg/L potassium hydroxide solution. The dyes were detected by absorbance at the wavelength of 214 nm. The linear range of the proposed methods varied from 63 to 7600 mug/L with a limit of detection ranging from 19230 mug/L by CE and varied from 73 to 5700 mug/L with a limit of detection ranging from 22-280 mug/L by HPLC regarding the assay of 500 mL of preconcentrated water sample.