Study of the flow development during the slurry packing of microcolumns for liquid chromatography

Gross flow development patterns have been monitored during slurry packing and compared for PEEK and stainless-steel liquid chromatographic microbore columns for different sorbents and slurry compositions. Flow-rate, pressure and apparent permeability data were collected with the help of a computer-aided monitoring technique. The development of the packing process under constant-pressure conditions, as detected by changes in the flow, has been found to have four characteristic stages, the development of which correlates with the final degree of compaction of the porous bed and with column efficiency. The parameters characterising porous structure - specific permeability, K-o, and specific column resistance, phi' - have been compared for different groups of packed columns. It has been found that they correlate weakly with the column efficiency and the packing pressure for the same group of sorbents and packing slurry chemical composition. However, packings performed under the same pressure regime but using differing slurry media produced different flow patterns and have shown vast variation both in the column efficiency and in the specific column resistance. The range of specific column resistance values observed in this study for 0.5-mm I.D. microcolumns was 250<phi'<900. A correlation of phi' with the column tubing material has been observed and attributed to wall effects. The proposed method for the assessment of the effectiveness of the packing procedure enables changes in the dynamics of the packing process caused by changes of the slurry chemistry or other packing parameters to be observed and thus, the packing procedure for new stationary phases to be effectively adjusted. The expected column efficiency (and particularly packing failure) can be estimated during packing, prior to chromatographic assessment of the column.