STUDY OF THE FLOW DEVELOPMENT DURING THE SLURRY PACKING OF MICROCOLUMNS FOR LIQUID-CHROMATOGRAPHY

Gross flow development patterns have been monitored during slurry pack ing and compared for PEEK and stainless-steel liquid chromatographic m icrobore 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 cha nges in the flow, has been found to have four characteristic stages, t he development of which correlates with the final degree of compaction of the porous bed and with column efficiency. The parameters characte rising porous structure - specific permeability, K-o, and specific col umn resistance, phi' - have been compared for different groups of pack ed columns. It has been found that they correlate weakly with the colu mn efficiency and the packing pressure for the same group of sorbents and packing slurry chemical composition. However, packings performed u nder the same pressure regime but using differing slurry media produce d different flow patterns and have shown vast variation both in the co lumn efficiency and in the specific column resistance. The range of sp ecific 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 caus ed by changes of the slurry chemistry or other packing parameters to b e observed and thus, the packing procedure for new stationary phases t o be effectively adjusted. The expected column efficiency (and particu larly packing failure) can be estimated during packing, prior to chrom atographic assessment of the column.