A chromatograph with on-line gamma-detector compatible with corrosive eluants is described. The interplay among chromatographic resolution, speed of analysis, and precision of a radio-activity detector is reviewed. The precision of the peak area measurement of a radio-chromatographic peak can be improved by incorporating a multiscaler in the counting circuit. The void volume and cation exchange capacity of a column packed with experimental monodisperse 9.8 μm, highly (>40%) crosslinked porous resin particles have been measured by different methods. Measured cation exchange capacity by isotopic exchange between (23Na)r+ (22Na)sand the titration method are identical. The variation of overall height equivalent to a theoretical plate for the isotopic exchange with flow rate is reported. The extrapolated value of plate height at zero flow rate is about 3.2 times particle diameter.