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What You Should Know About Filtration
An HPLC system is a sophisticated pumping system consisting of many expensive
precision components. Foreign particles introduced at any point can block
and/or seriously damage one or more of these components. But by following
a few simple procedures, you can protect your delicate system.
An HPLC filtration system can be looked at
in five parts:
| Solvent Filtration |
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| Pre-filter and store solvents in
a vessel that allows solvent to be pumped out and sparging gas to
be allowed in. An inlet solvent filter (or "sinker") on
the end of the pump inlet tube will filter the solvent again and hold
the tube at the bottom of the reservoir. |
| Inline Solvent
Filter |
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| Since pump-seal particles can break
off and block the injection valve or the column frit, use an inline
solvent filter with a 2µm filter disc immediately after the
pump to help prevent this. |
| Sample Filtration |
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| Before injection, samples should
be filtered. One option is to use a disposable sample filter attached
directly to your injection syringe; however, the choice of filtration
devices depends upon the volume of the sample. |
| Precolumn Filter |
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| A 2µm or 0.5µm filter
between the injector and the column will insure no particles suspended
in the mobile phase reach the guard or analytical columns. The internal
volume of a precolumn filter will generally be lower than that of
an inline filter, due to concern about volume after the injector.
The precolumn filter traps any material that would otherwise end up
on the frit at the entrance to the column. So why have a precolumn
filter with a column frit already there? Because changing the main
column frit risks disturbing the column packing, which can ruin your
column. The precolumn filter is therefore a risk-free, inexpensive
"insurance policy" to protect your expensive column. |
| Guard Column |
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| Guard columns also protect the analytical
column. They are typically packed with the same material as the analytical
column of the same inner diameter. It acts as a chemical filter, removing
strongly retained materials that would otherwise foul the main column. |
| Check to make sure your tubing is
seated properly |
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| When using universal Fingertight fittings, the tubing
must bottom out in the fitting before the nut and ferrule are tightened.
If, after tightening the fitting a gentle tug disengages your tubing,
remove fitting and try again. |
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