Ultrahigh Performance Liquid Chromatography U-HPLC

High performance 3-pm particles gained popularity in the early 1990s. For example, a fast ( 50 s) IPC determination of nitrite and nitrate on a short 3.0 cm x 0.46 cm 

3-pm reversed phase column was validated against conventional ion chromatography 

The following section demonstrates that short colunms packed with sub-2-/an particles and run at high flow rates provide fast (several minutes) and ultrafast (seconds to a few minutes) separations while maintaining or improving resolution. 

Band broadening within the chromatographic column is described as a function of mobile phase linear velocity ( ) by the well known van Deemter equation [5] that relates the height equivalent to the theoretical plate (HETP) to u the lower the HETP, the higher the plate number per unit length of a column. It follows that the highest efficiency is obtained for the shortest HETP. The van Deemter equation is  

The A term is related to multipath effects (eddy diffusion) that are independent of mobile phase flow rate. Analyte molecules can follow multiple pathways of differing lengths that spread the analyte molecules apart and cause peak broadening. Since the smaller the particles, the lower the difference among molecule walks along the column, the A term is linearly dependent on particle diameter, d, according to X, a structure factor  

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