Comparison of three- and five-micrometer column packings for reversed-phase liquid chromatography

Temperature as a Variable in Pharmaceutical Applications

“…However, even early studies including those by Cooke et al [35] and by Poppe and Kraak [36] demonstrated that using a mobile phase slightly cooler than the column temperature can improve column efficiency. Usually, differences of 10-20°C gave the highest efficiency.…”

“…Some selectivity changes with temperature were noted. The low viscosity at 100°C also enabled very small 1-μm particles to be used for the separation of benzdiazepines (Figure 18 theobromine, theophylline, and caffeine when separation on a PBD zirconia column at 150°C took place in less than 1 minute compared to 7 minutes at 40°C on a Hypercarb column (Figure 18-7) [35].…”

Fundamental Relationships of Chromatography

“…From equation (1.16) it can be seen that the operating pressure required to maintain a constant mobile phase velocity is proportional to the ratio L/d 2 . Thus, the principal virtue of the use of small-diameter particle columns is that they permit a reduction in separation time for those separations that do not require an unusually large number of theoretical plates [217][218][219][220]. The theoretical efficiency (calculated assuming that the plate height equals twice the particle diameter) and relative column operating pressure referenced to a 25 cm column packed with 10-micrometer diameter particles for some typical packed column types are summarized in Table 1.14.…”

“…For long columns operated at high pressures and short, small particle columns operated at high flow rates a considerable amount of heat is generated due to frictional heating of the mobile phase during its passage through the column [217,218,[232][233][234][235][236]. Heat is generated at a constant rate over the whole length of the column.…”

High-Performance Liquid Chromatography for Determination of Trace Organic Compounds in Aqueous Environmental Samples

“…Eq 3 is derivable from an equation that expresses extracolumn solute band broadening by using component variances (26). Table IV also shows the maximum injection volumes allowed on the various columns by assuming a solute capacity factor of 4, k' = 4, and Β = 2.45 (25,27).…”