Some analysts may think that selection of a syringe filter
for their sample preparation step is of trivial importance. However, there is
more to the syringe filter than just membrane material (e.g. nylon vs. PTFE).
For instance, lower quality syringe filters may have extractable compounds that
can end up in your filtrate. These extractables then show up as unknown peaks
in your chromatograms, potentially interfering with peaks of interest. In a
study comparing AQ™ Brand NDX filters to those of market leaders, the AQ™ Brand
was shown to produce a lower peak area of the extractable and even more so
after an initial wash step.
Another
aspect to consider is the hold-up volume. Suppose you have a sample that is available
in limited supply. It could be expensive or simply rare. In this case, you
don’t want to waste any of the sample and that is exactly what happens in a low
quality filter. After the filtration, the amount of liquid remaining in the
filter membrane is called the hold-up volume. It is best to minimize this
volume and the MicroSolv AQ™ Brand NDX™ Depth Filters outperform competitive
filters in this respect.
If you
have to filter a large amount of liquid with a single syringe filter, then
lifetime becomes significant. The AQ™ Brand was shown to have a comparable
lifetime to competitive filters. These three aspects of the syringe filter
should not be overlooked as they can all cause unnecessary problems for the
analyst.
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