CAPILLARY ELECTROPHORESIS OF CATIONIC AND ANIONIC SURFACTANTS WITH INDIRECT CONDUCTIVITY DETECTION

Anions such as F-,Cl-, Br- and SCN- and cations such as Li+ and Na+ ha ve been investigated as electrolytes for the capillary electrophoresis (CE) separation of aliphatic surfactants with indirect conductivity d etection (ICD). The ICD results have shown that the signal-to-noise or der is F- > SCN- = Br- = Cl- for the anion electrolytes and Na+ > Lifor the cation electrolytes. A mixture of C12-, C10-, C8- and C6-SO3- can be separated in less than 5 min using 10 mM F- and 1 mM triethanol amine (TEA) prepared in triply distilled water. A mixture of cationic quaternary ammonium surfactants can be separated in less than 3 min us ing 10 mM Na+ and 1 mM TEA prepared in triply distilled water. Detecti on limits (about 6 mg/l) for the surfactants by ICD are presently not as favorable as those previously obtained by indirect photometric dete ction. Use of NaF as the electrolyte did permit the simultaneous CE se paration of anionic and cationic surfactants with ICD in the presence of an aromatic non-ionic surfactant. (C) 1997 Elsevier Science B.V.