||Capillary isotachophoresis is an electrophoretic technique related to capillary zone electrophoresis. The primary advantage of isotachophoresis is the ability to greatly increase the on-column concentration of the analytes by choice of appropriate electrolyte systems. Such a system enhances the detection of low level impurities in a sample. Identification and quantitation of such impurities is of particular interest in pharmaceutical analysis. A closely related technique is transient capillary isotachophoresis/capillary zone electrophoresis (CITP/CZE). This technique employs only a short isotachophoretic concentration step followed by a normal zone electrophoresis separation. The CITP/CZE technique offers more practical applications than classical isotachophoresis and permits direct quantitation of the analytes. Applications described in the thesis include: (1) optimization and use of the transient capillary isotachophoresis/capillary zone electrophoresis technique for the simultaneous determination of inorganic anionic impurities and acetate salt counter-ion in a pharmaceutical drug substance, (2) direct quantitation of heavy metals in a pharmaceutical drug substance.