Selectivity and efficiency measurements in high-performance liquid chromatography using micellar hexadecyltrimethylammonium bromide in the mobile phase
Good chromatographic efficiency in high-performance liquid chromatography (HPLC) was obtained using micellar hexadecyltrimethylammonium bromide (CTAB) in the mobile phase. Dithiocarbamate salts of varying hydrophobicity were used as test solutes. The efficiency measurements obtained for the hydrophobic solutes (phenol and benzene) were compared with those obtained for the ionic dithiocarbamate salts. The influence of CTAB concentration above the critical micellar concentration on retention, efficiency and selectivity and the effects of varying the concentration of organic modifier on the efficiency and retention with a micellar CTAB mobile phase were investigated.The chromatographic efficiency remained high when methanol was used as the mobile phase modifier. When acetonitrile was used as the modifier, the efficiency obtained was poor. Conductance measurements present a possible explanation for the difference in efficiencies obtained for these widely used mobile phase modifiers. The measurements obtained with a micellar mobile phase were compared with those obtained with a non-micelle forming quaternary ammonium salt, tetrabutylammonium bromide.