Waters XSelect CSH HPLC Columns - Manual (Page 3)

[ CARE AND USE MANUAL ]
3 XSelect CSH HPLC Columns
II. COLUMN USE
To ensure the continued high performance of XSelect CSH columns, follow these guidelines:
a. Guard Columns
Use a Waters guard column of matching chemistry and particle size between the injector and main column. It is important to use a high-
performance matching guard column to protect the main column while not compromising or changing the analytical resolution.
Guard columns need to be replaced at regular intervals as determined by sample contamination. When system backpressure steadily
increases above a set pressure limit, it is usually an indication that the guard column should be replaced. A sudden appearance of split
peaks is also indicative of a need to replace the guard column.
b. Sample Preparation
1. Sample impurities often contribute to column contamination. One option to avoid this is to use Waters Oasis ® solid-phase extraction cartridges/columns
or Sep-Pak ® cartridges of the appropriate chemistry to clean up the sample before analysis.
2. It is preferable to prepare the sample in the operating mobile phase or a mobile phase that is weaker (less organic modifier) than the mobile phase for the
best peak shape and sensitivity.
3. If the sample is not dissolved in the mobile phase, ensure that the sample, solvent and mobile phases are miscible in order to avoid sample and/or buffer
precipitation.
4. Filter sample with 0.2 µm filters to remove particulates. If the sample is dissolved in a solvent that contains an organic modifier (e.g.,
acetonitrile, methanol, etc.) ensure that the filter material does not dissolve in the solvent. Contact the filter manufacturer with solvent
compatibility questions. Alternatively, centrifugation for 20 minutes at 8,000 rpm, followed by the transfer of the supernatant liquid to an
appropriate vial, could be considered.
c. Operating pH Limits
The recommended operating pH limits for XSelect CSH columns are listed in Table 2. A listing of commonly used buffers and additives is given
in Table 3. Additionally, the column lifetime will vary depending upon the operating temperature, type and concentration of buffer used.
Table 2: Recommended pH and Temperature Limits for XSelect CSH columns
Columnn Name Particle Size (µm) Pore Diameter (Å) Surface Area (m 2 ) pH Limits
Temperature Limits (°C) Ligand Density
(µmol/m 2 )
% Carbon
Low pH High pH
XSelect CSH C
18
2.5, 3.5, 5, 10 135 185 1-11 80 45 2.3 15
XSelect CSH Phenyl-Hexyl 2.5, 3.5, 5 135 185 1-11 80 45 2.3 14
XSelect CSH Fluoro-Phenyl 2.5, 3.5, 5 135 185 1-8 80 45 2.3 10
Note: Working at the extremes of pH, temperature and/or pressure will result in shorter column lifetimes.