How to Use Syringe Filter?

In many laboratories such as modern life sciences, drug analysis, environmental monitoring, sample filtration is a basic and crucial link. Syringe filters, as an efficient and convenient filtration consumable, are widely used in the pretreatment process of various liquid samples to ensure sample purity, protect precision instruments, and improve experimental accuracy, the most widely used filtering tools are 0.22µm and 0.45 um syringe filter. This article will give a comprehensive introduction to the definition, structure, material, usage, selection recommendations and application scenarios of syringe filters to help researchers and purchasers better understand and use this key consumable.

What is a syringe filter？

A needle filter is a small disposable filtration device, usually used with syringes, liquid chromatography systems (HPLC) and other equipment. Its outer shell is mostly made of polypropylene (PP) or polycarbonate (PC), and a microporous membrane is integrated inside to intercept particulate impurities, microorganisms or colloidal contaminants in the sample. The typical structure of a needle filter includes:

Upper cover: used to connect the syringe
Filter membrane assembly: the core part of the actual filtration
Housing: encapsulates the entire structure
Liquid outlet: usually a Luer interface (Luer Slip or Luer Lock)

Filtered syringes have the advantages of easy operation, small size, high filtration efficiency, and avoidance of cross contamination. They play an important role in laboratory sample processing, instrument injection protection, and solvent purification.

What is a syringe filter used for？

1. Sample Clarification Before Analysis One of the most common uses of filter for syringe is clarifying solutions by removing particulates. Before injecting samples into high-performance liquid chromatography (HPLC), gas chromatography (GC), or other analytical instruments, filtration helps prevent clogging, protect the instrument, and ensure reliable data.

2. Sterile Filtration Syringe filters with 0.22 μm or 0.45 μm pore sizes are often used to sterilize aqueous solutions, cell culture media, or biological reagents by removing bacteria and other microbes. This is especially important in microbiology, molecular biology, and cell culture applications.

3. Protein and DNA Purification Some specialty syringe filters are used in the preparation and cleanup of nucleic acids and proteins. Filtration helps remove cell debris or aggregates prior to analysis or storage.

4. Solvent Filtration In chemistry and pharmaceutical labs, syringe filters are used to remove undissolved particles or precipitates from organic solvents, ensuring the purity of the solvent and the accuracy of the experiment.

5. Environmental Sample Processing In environmental testing, syringe filters are used to filter groundwater, wastewater, or other environmental samples prior to testing for contaminants or pollutants.

6. Pharmaceutical and Vaccine Preparation Syringe filters are used during the formulation or preparation of sterile injectable drugs or vaccines, ensuring that no particulate contaminants are introduced into the final product.

How to use syringe filter?

Choose a filter of appropriate specifications to ensure that the material and pore size are compatible with the sample.
Use a syringe to draw the sample to be processed and ensure that there are no bubbles in the liquid.
Connect the needle filter to the syringe interface to keep the interface well sealed.
Slowly push the syringe plunger to filter the sample at a constant speed to prevent excessive pressure from causing the membrane to rupture.
After filtration, the filtrate can be used directly for analytical instrument injection or subsequent experiments.

What substances can syringe filter 0.22 μm and syringe filter 0.45 micron？

Substances that can be filtered by 0.22 filter syringe

1. Bacteria
It can effectively remove most bacteria, including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, etc.

It is often used for sterile filtration or sterilization-grade filtration.

2. Particles and suspended matter
It can filter insoluble particles larger than 0.22 microns, such as tiny dust particles and cell fragments.

Substances that can be filtered by 0.45 μm syringe filter

1. Large particle impurities
It can effectively remove suspended particles, cell debris, pollutants and some large bacteria.

2. Weak bacterial filtration ability
It cannot completely remove all bacteria and cannot be used for strict sterile filtration.

Can 0.22 μm syringe filters and 0.45 um syringe filter millipores be reused?

Because the structural design of the micron filter syringe makes it difficult to clean, there is a risk of cross-contamination, and the filtration efficiency and integrity are reduced, so reuse is not recommended.

How to choose syringe filter?

1. Choose based on the filter membrane material
The filter membrane material of the needle filter determines its chemical compatibility, hydrophilic/hydrophobic properties, and applicable solution types. Common filter membranes include:

MCE filter syringe: naturally hydrophilic, easy to wet, low protein adsorption, good compatibility with aqueous solutions, suitable for filtering samples sensitive to biomolecules.
PES syringe filter: low protein adsorption, hydrophilic, suitable for tissue culture fluid, biological sample filtration, especially for applications requiring high flow rates.
Nylon syringe filters: wide chemical compatibility, hydrophilic, suitable for filtering most organic solvents and aqueous solutions. But not suitable for strong acids and alkalis.
PTFE sterile syringe filter : It is extremely hydrophobic and suitable for filtering highly corrosive solvents, such as strong acids, strong bases, and organic solvents. It can also be used for gas filtration. It can also filter aqueous solutions after pre-wetting.
PVDF syringe filters: It has good chemical compatibility and low protein adsorption, and is often used for filtering biopharmaceutical samples.
CA sterile filter: It is hydrophilic and has low protein adsorption. It is suitable for filtering biological samples and water-based solutions, but it is intolerant to organic solvents.

2. Choose according to pore size
The pore size of the filter membrane determines the filtration accuracy. The most common pore sizes are:

Syringe filters 0.45 micron: used for pre-filtration of conventional solutions and removal of particulate impurities, suitable for chromatographic pretreatment.
Syringe filter 0.22 micron (or 0.20 μm): used for sterile filtration with higher requirements, which can remove bacteria and other microorganisms.
Smaller pore size (such as 0.1 μm): mainly used for virus filtration or extremely high purity requirements.

If there are many particulate impurities in the sample, you can first filter with 0.45 μm, and then use 0.22 micron syringe filter for secondary fine filtration to prevent clogging of the filter membrane.

3. Choose according to the filter size

The diameter of the needle filter affects its filtration volume and flow rate. Common specifications are:

13 mm: Suitable for small volume samples (<10 mL), routine laboratory use.
25 mm: Can handle medium volume samples (<100 mL), faster flow rate, and more widely used.
30 mm and above: Suitable for larger volume filtration, suitable for batch processing or industrial applications.

4. Hydrophilic or hydrophobic selection

Hydrophilic syringe filter: Can directly filter aqueous samples or polar solvents without pre-wetting. Commonly used for buffer solutions and biological samples.
Hydrophobic membrane: More suitable for organic solvent, air and gas filtration. If it is used for aqueous solutions, it must be pre-wetted with ethanol or isopropanol.

Summary

Syringe filters are indispensable tools in modern laboratories. Whether you’re preparing samples for analysis, sterilizing solutions, or purifying biological macromolecules, these small devices offer speed, precision, and protection for both samples and equipment.

At SDLABIO, we are committed to providing high-quality, sustainable, and efficient laboratory plastic consumables, including syringe filters designed to enhance your filtration experience. Explore our website to discover our product range, and feel free to contact us for expert advice or tailored solutions to meet your needs.