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High-Load Columns
When the objective is to isolate milligram quantities of material,
larger diameter columns are packed with the same high-performance packings as their
analytical counterparts, making method transfer simple. When scaling up from a 4.6 mm ID
column to a 10 mm ID column, flow rate should be increased by a factor of 4.7 to maintain
an equivalent linear velocity and hence an equivalent separation time.
High-Sensitivity Columns
Narrowbore HPLC has made some routine high-sensitivity separations
possible. High-sensitivity HPLC is especially useful in applications where sample sizes
are limited, when the cost of mobile phase additions is very high or when solvent disposal
is concern.
For highest sensitivity, use Beckman Coulter 5 micron Ultrasphere
narrowbore columns, available in 2mm ID and 150 mm or 250 mm lengths.
High-Speed Columns
One of the primary reasons for using fast HPLC is to improve sample
throughput. Most separations, particularly simple ones, can be speeded up by more than two
times without adversely affecting resolution. Fast HPLC performs best when the selectivity
ratio Q is greater than 1.08 and the separation is isocratic.
For high-speed separations, start with a 75 x 4.6 mm Ultrasphere column
packed with 3 micron media (the same chemistry as the 5 micron media)
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