The Impact of Column Hardware on Efficiency in Liquid Chromatography (LC)

Column hardware in liquid chromatography-that is, the tubing, the frits, and fitting-has a strong influence on separation performance or the reproducibility of chromatographic data. Flow distributors and frits can introduce serious band broadening when separation is performed in short, narrow-bore columns. The kinetic performances of packed and monolithic columns are usually similar for well-retained analytes. However, monolithic columns may show significantly better performance for early-eluting compounds, which can be attributed to the moderate mobile phase dispersion caused by the simpler column hardware because no frits are required. Packed columns are axially heterogeneous, and some differences can be observed between the two respective column ends as a result of the packing procedure. The sample band broadening in the immediate vicinity of the column ends can be characterized with flow-reversal experiments. Although flow-reversal has a peak compression effect, and the peaks observed with reversed flow are always narrower and more symmetrical than the peaks obtained without reversing the flow, flow-reversal can be a useful tool to show the differences between the intrinsic plate heights of the packed or monolithic bed and for showing the differences between the two respective column ends. Shorter columns are axially more homogeneous than longer ones, thus the column length is an influencing factor on the column packing procedure.