Determination of cations in water and biological fluids by capillary zone electrophoresis

The parameters of greatest importance in the process of Capillary Electrophoresis (CE)-buffer pH, voltage, temperature, and buffer concentration-were studied in respect of their influence upon the migration times (t(m)) of the following cations: Na+, K+ Ca+2, Mg+2, Ni+2, Zn+2, Fe+2, and Mn+2. With the figures obtained from this research it proved possible to understand, in greater depth, the behaviour of these cations in this modern analytic technique. The data obtained permitted the design of an analytical procedure using CE with the optimal combination of values for each variable. This was thereafter applied to the analysis of these cations in samples of water, milk, blood plasma, and urine. The conditions seen as the most suitable were the following: the electrolyte was an aqueous solution of imidazole 15 mM, pH = 4.0, voltage V = 15 kV, and temperature T = 30 degrees C. The procedure proved to have good precision, linearity, a coefficient of correlation CC = 0.999, and detection limits for the cations involved of between 0.01 and 5.00 ppm.