FAQ
Syringe filters are single-use filtration devices that are made up of a membrane, or combination of membranes, placed inside molded housing. The connections on the device are commonly Luer lock or Luer slip and enable a quick connection to syringes, that are used to pass the liquid sample through the filter.
There are multiple membrane types, pore sizes, and housing material variants.
Syringe filters are chosen based upon suitability to a user's application. Syringe filters are typically split in five categories, based upon the user applications:
- Analytical sample preparation filters
- General clarification and sterile filtration filters
- CE mark Medical Device filters
- Specialty filters, such as those with activated carbon and
- Venting filters for air and gases
Syringe filters are typically single-use and should not be reused as syringe filter performance is based upon the first filtration. Reuse may negatively impact performance and sample results, due to causing cross-contamination, loss of sample, or blockage due to membrane fouling. However, reusable syringe filter holders are available that utilize replaceable membranes.
There are several methods of sterilization, such as gamma irradiation, e-beam, ethylene oxide gas exposure, and autoclaving. It is recommended to use devices pre-sterilized by the manufacturer if sterilization is required, to ensure performance and certified sterilization. Alternatively, some devices may be autoclaved in the lab, but this should be checked for each device.
Primary uses of syringe filters are the general clarification of particles from a liquid or air/gas samples, the sterile filtration of a sample to remove bacteria, the removal of particles and suspended solids prior to analytics such as HPLC. Syringe filters may also be used for gas venting, allowing clean, sterile air to pass through in vessels such as bioreactors.
Glass Microfiber Filters (without binder) are made of 100 % borosilicate and have a temperature resistance up to 500 °C or max. 550 °C; with binder, they have a lower temperature resistance up to 180°C.
Quartz microfiber filters manufactured with 100 % quartz (silica, SiO2) have the highest temperature resistance up to 900°C.
In terms of purity, you will get the highest purity with filters made 100 % of quartz, followed glass microfiber filters without binders. Binders increase the mechanical stability of the filter but reduce its purity.
All are depth filters - they do not have pores, as they are made of fibres with an irregular structure. Therefore, the particle retention properties are only a rough information. Different sizes of particles are retained on the surface of the filter as well as in its depth structure. They are therefore ideal for the filtration of high loaded solutions, but they cannot be used as sterile filter for which you need a defined pore size.
Glass microfiber filters have a higher loading capacity than filter papers and are therefore better suitable as prefilters; they will not clog easily.
One side of the filter is smoother than the other one, due to manufacturing processes. Because of the irregular fiber structure of depth filters, you can use any side for filtration and obtain the same results.
