Cation exchange chromatography with both unsuppressed conductivity detection and indirect photometric (IPD) modes were used for the separation and detection of inorganic cations. Salt of weak base diphenylamine has been used as an eluent for several cations both with unsuppressed conductivity detection and IPD. Diphenylammonium chloride possess ion exchange capability, chromatographic selectivity and large molar absorptivity.Diphenylammonium chloride has shown a good chromatographic performance toward the analysis of some cations such as (Lithium, Sodium, Potassium, Magnesium and Calcium) using conventional HPLC equipment with either conductivity or indirect UV detectors. The analysis of these cations using (1×10-7 M) diphenylammonium chloride at pH 4.90 in 6% methanol, with Dionex Ion Pac CS3 Column, and 1ml/min flow rate was achieved with unsuppressed column conductivity and IPD at 297.5 nm detection. Chromatogram of a separation mixtures containing five cations (Li+, Na+, K+, Mg+2 and Ca+2) and other mixture have given well separated peaks.The capacity factor k' for the analyzed cations were ranged from (1.80-6.71), peak asymmetries was ranged from (1.10-1.83) and resolution with an average value of (1.665) was obtained.The RSD in tR averaged 0.435 %. The average recovery was 92.856 % and the relative error percentage was averaged 7.144 % with unsuppressed conductivity etection.However, using IPD, the peak symmetry was ranged from (1.30-1.95), and an average value of resolution of 2.2025 which indicate a good chromatographic performance. The RSD in tR averaged 0.351%. The average value of recovery was 94.942 %.Calibration curve for all analyzed cations were linear from their detection limits to at least 25 ppm. The correlation coefficients for the linear calibration curve were ranged from (0.9991-0.9999) with both detection techniques. The detection limit was ranged from (0.15-0.35) ppm using unsuppressed conductivity detection compared to (0.10-0.25) ppm with IPD.
