Small particle liquid chromatography dispersion

The small peak volumes typical of samples eluted from small bore columns and short small diameter particle columns used in high-speed liquid chromatography place severe demands on the dispersion characteristics of all components of the liquid chromatograph. The standard deviation of a peak eluting from a column is given by... 

In the first approximation, the column packed with small particles can be considered an array of capillaries. Hydrodynamic processes augment the exclusion based separation (see section 11.7.2, Retention Mechanisms and Accompanying Processes in SEC) and form the ground of a liquid chromatography-like method called hydrodynamic chromatography, HDC. HDC found application in separation of veiy large macromolecules, particles and dispersions. Its separation selectivity is rather low and it was partially substituted by the group of methods termed fieldflow fractionation (see seetion 11.3.3, Molar Mass Dispersity). 

In MSPD, sample is completely disrupted and dispersed into particles of very small size, which enhances a surface area required for subsequent extraction of the compounds, whereas in solid-liquid (SL)-SPE, sample disruption must be carried out separately and several compounds must be discarded before an extractive solution is found suitable for application on SPE column. While in SPE the extracted compounds are usually absorbed onto the top of the column packing material, in MSPD they are absorbed throughout the column. Physical and chemical interactions among the components of the system are greater in MSPD than those occurring in classical SPE or other forms of liquid chromatography (LC). 

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