FACTORS INFLUENCING TRACE ION ANALYSIS WITH PRECONCENTRATION BY ELECTROSTACKING

Capillary electrophoresis with indirect UV detection and electrostacking achieves low mu g/l detection limits for inorganic anions and cations in various low conductivity matrices. Since this technique requires electromigration injection, parameters such as analyte electrophoretic mobility, electroosmotic flow, and sample and operating buffer ionic strength influence the amount of material that is actually injected into the capillary. These parameters are not easily controlled and are affected by such factors as injection voltage and duration, operating buffer, and operating buffer pH. The effects of these factors on sensitivity and resolution are demonstrated. The use of a novel carrier ion, dimethyldiphenylphosphonium ion, improves sensitivity for cations. Techniques for optimizing trace level determinations are also discussed.