A filter needle is a membrane-based product used to remove specific impurities from fluid samples, such as bacterial contamination. In many laboratories, filter needles are used for effective and quick filtering, sterilization, and material purification.
Why is it important to choose the right Filter Needle?
All analytical processes that require test sample filtration are critical. Even minor errors can have a significant impact on the entire process and, ultimately, the results. Using the correct filter needle allows you to obtain accurate results while also expediting the discovery or diagnosis process.
In all analytical tests, selecting the correct filter needle is critical. When choosing a filter needle, several factors must be considered. We’ve discussed some of the most important factors to consider when making a decision.
Body of the Filter
The filter body is chosen based on the sample to be filtered. The filter body can be disposable and is typically made of polypropylene. It is also reusable and is typically made of polycarbonate and stainless steel.
Select a Pore Size That Is Appropriate
The pore size of the filter needle is chosen based on the size of the particles to be filtered out of the aqueous solution. Most of the time, filter needles are available in 05 µm, 0.10 µm, 0.22 µm, 0.45 µm, 0.70 µm, 0.80 µm, 1 µm, 3 µm, 5 µm, and 10 µm sizes. In laboratories, 0.2 um and 0.45um pore size filters are most commonly used. The greater the pressure required to pass the sample through the syringe membrane filter, the smaller the pore size.
Diameter of the Filter
The diameter of a filter needle is determined by the volume of the sample to be filtered. If the aqueous sample volume is larger, the filter should have a larger diameter. filter needles come in a range of sizes, including 4mm, 13mm, 17mm, 20mm, 25mm, 30mm, and 33mm. Filters with a diameter of 4mm are used for smaller volume samples (approximately 1 ml), while filters with a diameter of 30mm are used for larger volumes (approximately 100 ml).
Material of the Membrane
The following key aspects should be considered when selecting membrane material. The commercially available membrane materials are listed below.
- Cellulose Nitrate(CN)
- Cellulose Acetate (CA)
- Nylon Membrane
- Glass Microfiber (GMF)
- Polyethersulfone (PES)
- Polypropylene (PP)
- Polytetrafluoroethylene (PTFE)
- Polyvinylidene Difluoride (PVDF)
- Regenerated Cellulose (RC)
Compatibility with Chemicals
When selecting a syringe membrane filter, consider whether the filter’s material can withstand the chemical nature (Acidic or Basic) of the aqueous solution.
The Flow Rate
Membrane flow rate is also an important consideration when choosing a membrane material.
The membrane’s natural hydrophilicity or hydrophobicity must be considered. Hydrophilic filters keep out other molecules while allowing water to pass through the membrane. Hydrophilic filters include polyethersulfone (PES), Nylon, Cellulose Acetate (CA), Regenerated Cellulose (RC), Anopore, Glass Fibre, and polypropylene.
Occasionally, naturally hydrophilic filters are insufficient to filter more acidic samples. Hydrophobic filters are pre-wetted during the manufacturing process to become hydrophilic. Hydrophilic Polytetrafluoroethylene and Hydrophilic PVDF (Polyvinylidene Fluoride) are hydrophobic filters that have been converted to hydrophilic filters.
Filters can be Sterile or Non-Sterile.
Sterile filter needles are preferred if a sterilized aqueous solution is required. Non-sterile filters can be used for samples that will be filtered again.
Type of Connection
filter needles typically have female luer lock inlets and male luer slip outlets. Filters can, however, be designed with double luer lock connections, a female luer lock inlet and a male luer lock outlet, to achieve secure and tight sealing.