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Filtration of Contaminants
Frits, also referred to as filters, remove contaminants. Within HPLC in order to achieve
ultra sensitive results, it is vital to start with a clean mobile phase. There are a
number of methods required to obtain a clean mobile phase.
As you know, only very pure solvents should be used for the HPLC. Solvent impurities
can result in baseline shifts and detector noise. Impurities will contaminate collected
fractions and, if present in the weak eluent of a gradient separation, can cause ghost
peaks in the chromatogram.
External Filtration
Considering the time and effort required producing pure solvents, the cost of
commercial HPLC grade solvents is usually justified. However, all eluents, even those made
from HPLC grade solvents, require further preparation. Preparation steps include:
- drying
- degassing
- filtering
Both the eluent and the sample must be filtered for several reasons:
- particles can prevent a check valve from sealing properly
- particles can scratch piston seals causing them to leak
- particles will accumulate on the column frit and plug it
There are two methods for external filtration:
- Solvent filter/degassers
- Disposable syringe filters
Solvent Filter/Degassers
Because of the glass
construction, Agilent degassers assure you of minimum contamination from contact with plastics.
Additional benefits of using the degassers include:
- degas eluents as particulates are removed
- eliminate spurious peaks caused by outgassing in detectors
- eliminate pump downtime caused by air locks and particulates in check valve
- decrease piston wear; increase column life
- filter safely into plastic-coated or heavy-walled solvent reservoirs
- take all standard 47 mm filter membranes.
Disposable Syringe Filters
Syringe filters are convenient for filtering the sample. Agilent offers a
variety of different membrane types and pore sizes. The filters are all based on cellulose
materials that because of carefully controlled pore sizes offer good flow rates with
minimal flow resistance.
In-line Filtration
For in-line method filtration, the Agilent HPLC instrument provides intake and
outlet filters installed within the system to trap wear particles. The three types of
filters within the Agilent 1100 HPLC system are the inlet filter, the inlet valve and the
outlet filter.
It is important to change all filters on a regular basis to prevent instrument
malfunctions.
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