Separation of ions in acidic solution by capillary electrophoresis
Capillary electrophoresis (CE) is an effective method for separating ionic species according to differences in their electrophoretic mobilities. Separations of anions are usually achieved by adding a quaternary ammonium salt to the electrolyte solution to reverse the electroosmotic flow (EOF). It is now shown that excellent separations of inorganic anions such as the anionic chloro complexes of the platinum group elements (PGEs) and anionic metal oxides are obtained using an acidic aqueous electrolyte carrier. The EOF is minimized at an acidic pH which eliminates the need to reverse it. The acidic solution also helps to stabilize some analytes such as metal ions.;CE separations of amino acids by direct detection are difficult due to their similar electrophoretic mobilities and low absorbances. However, native amino acids can be separated by CE as cations at a low pH by adding an alkanesulfonic acid to the electrolyte carrier which imparts selectivity to the system. Derivatization is unnecessary when direct UV detection is used at 185 nm.;Capillary electrophoresis can be used under more acidic conditions than previously used for the detection of metal cations. CE can be used to detect UV absorbing metal cations directly in an aqueous electrolyte carrier near pH 2 with a detection wavelength of 185 nm or 214 nm. Simultaneous speciation of metal cations such as vanadium (IV) and vanadium (V) can easily be performed without complexation prior to analysis. An indirect UV detection scheme for acidic conditions was also developed using guanidine as the background carrier electrolyte (BCE) for the indirect detection of metal cations.