A novel functional form for describing the binary K-p data obtained with concentration pulse chromatography has been developed. The application of the novel function set was evaluated by studying the binary CO2-CH4 and CO2-N-2 systems using H-ZSM-5 as the adsorbent with SiO2/Al2O3 ratios of 30 and 280. Pure isotherms at 40 degreesC, up to 100 kPa pressure and binary isotherms at 40 degreesC and 100 kPa total pressure have been determined using the concentration pulse method. The results from the use of the novel function set show that a small deviation of the regression curve from the experimental data will result with differences in the binary isotherms.