Flow and Backpressure

The particle size of packing materials in conventional columns is typically 3 or 5 pm, while the ultrahigh-pressure systems utilize 1.7-1.9 pm particles, with 2.5 pm 

The backpressure resulting from pumping the mobile phase through the column 

the backpressure is doubled by doubling the column length. When the particle size is reduced from 5 to 3 pm, the pressure increases almost three times with the same column length. 

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A flow rate of 1.0 mL/min is adequate. Faster flows may be used to speed up the process if these higher flows (and backpressures) are compatible with your instrument. 

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