- The back pressure increase can be due to clogging of a column or clogging of the equipment. First of all, identify the clogging site.
- Disconnect the system components one by one to identify the clogged component(s). Start by disconnecting the column from the system and measuring the flowing mobile phase's pressure. The pressure should be close to zero. If the flow pressure without a column is normal, then the pressure increase is due to the clogged column.
- The cause of clogging needs to be determined and preventative measures implemented. The column may need to be replaced.
|
Cause |
Solution |
|
Salt deposit in the tubing. |
Disconnect the column and any other equipment
before pumping water through the tubing. Washing in a
reversing direction is also an effective way. If the situation does not
improve, replace the tubing with a new one. |
|
Cause |
Solution |
|
The
line filter of pump is clogged. |
Take
apart the line filter, and soak it in the solvent, then clean in an
ultrasonic cleaner. If the situation does not improve, replace the line filter with a new one. |
|
Cause |
Solution |
|
Manual
injector is clogged. |
Inject
with 20ml of contaminant dissolving solvent (e.g., methanol) by syringe. Wash
both lines in LOAD and INJECT position. Cleaning the injector in an ultrasonic bath is
also effective. If solids caused the clogging, wash the injector in a reversing direction. If the situation does not improve, replace the
injector with a new one. |
|
Cause |
Solution |
|
Salt
deposit in a column. |
Wash
columns for 30 minutes at half the normal flow rate using 10% organic solvent
(methanol or acetonitrile) in water to dissolve the salt deposits. If the situation does
not improve, wash the column with 100% water under the same condition. |
|
Cause |
Solution |
|
Column
frit is clogged by insoluble samples or impurities. |
Connect the column in
the reverse direction and disconnect it from the detector, and then wash the
column for 30 minutes at half of the usual flow rate with the same
mobile phase used for analysis. If the situation does not
improve, change the frit in the front end of the column (We can replace
end fittings with a paid service fee). |
|
Cause |
Solution |
|
Samples have adsorbed
to packing material or deposited in a column. |
Wash the column for 30 minutes with half of the normal flow rate using a solvent that can dissolve the adsorbed substances. Here are washing procedures for each column type. Reversed-phase columns a. When absorbed
substances are not proteins, wash with methanol or tetrahydrofuran. b. When absorbed substances are proteins, wash with 50-70% of acetonitrile/water (containing 0.1% of trifluoroacetic acid). However, proteins may precipitate in a high concentration of organic solvent. COSMOSIL SL-II Wash with methanol, tetrahydrofuran or ethanol. Fullerene columns Wash with o-dichlorobenzene, 1,2,4-trichlorobenzene. COSMOSIL Sugar-D/NH2/HILIC columns Wash with 50/50 (v/v) acetonitrile/water for
NH2-MS and 100% water for Sugar-D and HILIC columns. |
- Choose appropriate pretreatment for each sample.
- use guard columns.
- When wash columns, do not connect the column outflow end to the detector. Let the solvent flow into waste.
- Excessive washing may deteriorate the performance of columns.
- Do not use strongly alkaline solution (more than pH 7.5) or a strongly acidic solution (less than pH 1.5) for silica-based packing material.
- Store columns in manufacturer recommended storage solvent after washing.
- If the column performance does not improve after washing, replace the column.
|
Cause |
Prevention |
|
Contamination of
column due to normal long-term use. |
Wash the
column. |
|
Column damage due to
normal long-term use. |
Replace
the columns. |
0 Comments