Micro, capillary and chip HPLC

Most columns used for HPLC separations nowadays have an internal diameter of 

although they use double the amount of solvent and the performance is not better than with the 3.2 mm i.d. columns. There are many good reasons why the diameter should, in fact, be reduced even further  

Columns fall into three different categories  

Practical High-Performance Liquid Chromatography, Fifth edition Veronika R. Meyer 

Open capillaries of Spin i.d. and with 10 theoretical plates are rather easy to prepare. Theory shows that a capillary of i.d. 10 pm scores over a packed column as regards peak capacity, resolution and analysis time. The equipment poses a problem that is not insoluble (injection volume 50 pi, flow rate 2nlmin ). 

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