DETERMINATION OF AMMONIUM, SODIUM, POTASSIUM, MAGNESIUM, AND CALCIUM CATIONS IN RAIN WATER BY COLUMN-COUPLING CAPILLARY ISOTACHOPHORESIS

Separation conditions suitable to the isotachophoretic determination o f K+, Na+, NH4(+), Ca2+, and Mg2+ cations in rain water are described. The use of column-coupling ITP instrument with the electrolyte system enabling a complete resolution of the studied cations provided the li mits of detection in the range of 0.4-2.1 mu mol dm(-3) for a 30 mm(3) sample injection volume when the detection was carried out with the a id of a conductivity detector. Rapid (ca. 10 min analysis time) and re producible determinations (typically 5 % relative standard deviations) were achieved. Recoveries of the analytes in rain water samples on mu mol dm(-3) concentration levels ranged from 94 to 120 % with the extr eme values being typical for the analyte concentrations close to the l imits of detection.