COMBINED LIQUID-LIQUID ELECTROEXTRACTION-ISOTACHOPHORESIS FOR LOADABILITY ENHANCEMENT IN CAPILLARY ZONE ELECTROPHORESIS MASS-SPECTROMETRY

Combined liquid-liquid electroextraction (EE) and isotachophoresis (ITP) as a fast on-line focusing step in capillary zone eIectrophoresis (CZE) prior to electrospray mass spectrometric (ESP-MS) detection is described. Very high electric field strengths can be applied owing to the low conductivity of the organic phase, which results in high migration rates. Liquid-liquid electroextraction enables the fast extraction of analyte ions into a small buffer volume, whereas ITP is used to focus the analytes away from the liquid-liquid interface. As a result, ITP starts with a small sample volume containing the extracted ions. After reaching the steady state within several minutes, CZE separation follows. Clenbuterol, salbutamol, terbutaline and fenoterol were used as model compounds. Concentration detection limits of pure solutions down to 2.10(-9) mol/l for clenbuterol, salbutamol and terbutaline,and 5.10(-9) mol/l for fenoterol have been achieved using on-line EE-ITP-CZE-ESP-MS.