The effect of column end structure and bed heterogeneity of six commercially available reversed-phase chromatographic columns for fast liquid chromatography with different column packing materials - such as fully porous (Waters XBridge C18 with 1.7 μm particles) and superficially porous (Waters CORTECS C18 with 1.6 μm particles), with column dimension of 2.1 × 50, 100 or 150 mm were tested with flow-reversal method. The method includes arresting the flow when a non-retained marker (thiourea) has penetrated to a given distance into the column and then reversing the column. Hence, when the flow has been restarted, the sample is eluted at the same end of the column where it entered. The experiments showed that all columns are axially heterogeneous, and some differences could be observed between the two respective column ends. Furthermore, we can conclude that the shorter columns are axially more homogeneous than the longer ones, thus the column length is an influencing factor on the column packing procedure.
Keywords: Column packing; Flow-reversal; Packed bed heterogeneity; Sub-2-μm particles; UHPLC.
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