Retention in high-performance liquid chromatography at −196 °C

- Retention model in HPLC at −196 °C is proposed by adsorption exchange and pseudo partition.
- The proposed equation agrees well with the experimental results.
- Adsorptive retention is reduced effectively using highly adsorptive additives.
- Pseudo partitive retention is reduced effectively using high solubility mobile phases.
- Combination of stationary and mobile phases will control the k of various analytes.

Recently, we have developed ultralow-temperature high-performance liquid chromatography (HPLC) at −196 °C using liquid nitrogen-based mobile phases. In this study, a retention model for ultralow-temperature HPLC, in which adsorption exchange and “pseudo partition” modes are combined, is proposed to describe the effect of the mobile phase composition on the retention of analytes. The experimental results agreed well with the equation of the proposed model. It was revealed that, in the low and high additive concentration regions, adsorption exchange and pseudo partition retention, respectively, dominate the analyte retention. The difference in the retention behavior between bare-silica and octadecylsilyl-modified silica (ODS) columns was also studied. Retention of alkanes in the ODS column was greater than that in the bare-silica one. Addition of both ethane and ethylene to the mobile phase in the ODS column afforded the elution of propylene, which was not eluted with the bare-silica column at −196 °C.