Improved selectivity of anions with methanol as additive determination of Cl-, NO3- and SO42- in river water by capillary electrophoresis

A method for separation and determination of Cl-, NO3-, and SO42- in river water by capillary electrophoresis with indirect UV detection was described . A background electrolyte consisting of sodium berate, chromate and cetylt rimethylammonium bromide (CTAB) was employed for the separation. Methanol a s additive was added to the system for improving separation selectivity of NO3- and SO42- through adjusting the elution order of anions. High concentr ations of SO42- did not interfere with the determination of NO3- because SO 42- was eluted later than NO3-. The effects of the concentration of sodium berate and CTAB on separation were also examined. The detection limits of C l-, NO3- and SO42- were 1.10(-7) mol/l. The concentration of Cl-, NO3- and SO42- in river water was determined quantitatively using NO2- as an interna l standard. Standard addition recoveries of the Cl-, NO3- and SO42- in the river water sample were between 89 similar to 105%. The results were consis tent with those obtained by ion chromatography. (C) 1999 Elsevier Science B .V. All rights reserved.