VARIABLES INFLUENCING THE DIRECT DETERMINATION OF HALOACETIC ACIDS INWATER BY REVERSED-PHASE ION-PAIR CHROMATOGRAPHY WITH INDIRECT UV DETECTION

A reversed-phase ion-pair chromatographic system for the direct determ ination of haloacetic acids in water has been optimized utilizing indi rect photometric detection. Acetic, chloroacetic, bromoacetic, iodoace tic, dichloroacetic and dibromoacetic acids were used to characterize the chromatographic system. The effect of temperature on retention tim e shows a non linear van't Hoff behavior indicating a change in the me chanism of retention at about 30 degrees C. Above 30 degrees C, retent ion times decreased proportionally to increases in the temperature of the column. Separations are achieved in the pH range of 3.5 to 6.3 wit h an optimum at ca. pH 5.4. Increases in the concentrations of KH2PO4, 1-hexanesulfonate (competing ion) and acetonitrile result in proporti onal decreases in capacity factors with some selectivity variations de pending on the analyte. Increases in the concentration of benzyltribut ylammonium ion (ion interaction reagent) resulted in increases in capa city factors with a usable range from 8 to 12 mM. Of the reversed phas es studied, Spherisorb C-18 yielded the optimal results for the acids studied. Linear calibration curves for these acids were obtained utili zing indirect UV detection with detection limits as low as 2 parts per million.