Studies on elution conditions for the determination of anions by suppressed ion-interaction chromatography using a graphitized carbon column

A new method has been developed for ion-interaction chromatography with suppressed conductivity detection and a new graphitized carbon packing, which is sintered from carbonic material at a high temperature. Combinations of various eluting agents, tetrabutylammonium hydroxide (TEA) and acetonitrile have been investigated to optimize the separation of eight common anions (F-, Cl-, NO2-, Br-, NO3-, SO42-, HPO42- and I-). Calibration curves were linear from 0.5 to 10 mu g/ml for F-, from 1.0 to 20 mu g/ml for Cl-, NO2- and NO3-, from 2.5 to 50 mu g/ml for Br- and SO42- and from 5.0 to 100 mu g/ml for HPO42- and I- with a correlation coefficient (r) of 0.999 or better. The relative standard deviations (R.S.D.s) of peak areas were between 0.2 and 0.9% for 10 repeated measurements. The application of this newly developed method was demonstrated by the determination of chloride, bromide and sulfate in pharmaceutical compounds using the direct injection method. The analytical results were within +/-2% (relative) of the theoretical value, and thus in good agreement with the theoretical value for each sample. (C) 1998 Elsevier Science B.V.