Choosing a welded filter suitable for special chromatographic analysis needs to comprehensively consider multiple factors such as membrane material, pore size, filter diameter, welding process, etc. The following are specific selection points:
Filter membrane material
According to the properties of the sample, if the sample is an aqueous solution and is neutral or acidic, nylon material is more economical and versatile, with hydrophilicity and alkali resistance; If it is a strong acidic or strong alkaline solution, polytetrafluoroethylene (PTFE) is more suitable as it has excellent chemical stability and can withstand strong acids and bases. For organic solvents such as methanol, acetonitrile, etc., polypropylene (PP) or polyvinylidene fluoride (PVDF) materials can be selected, which will not swell or precipitate impurities due to contact with organic solvents. If it is a protein or biological sample, PVDF or polyethersulfone (PES) material is a better choice to reduce protein adsorption and ensure sterility, and it is best to choose sterilized products.
Aperture size
Based on the selection of chromatographic column packing particle size: In high-performance liquid chromatography (HPLC) analysis, if the particle size of the chromatographic column packing is 3 μ m or less, in order to effectively filter out particles that may clog the chromatographic column, it is recommended to use a 0.22 μ m filtration product; If the particle size of the chromatographic column packing is above 3 μ m, a filtration product of 0.45 μ m can be used.
Filter diameter
According to the sample processing capacity, if the sample volume is between 2-10mL, a 13mm diameter filter head is usually selected; When the sample volume is greater than 10mL, a 25mm diameter filter head is more suitable. For larger volume samples, a 33mm diameter filter can also be considered.
welding process
Consider the pressure resistance and sealing performance: The welding process of the welded filter directly affects its pressure resistance and sealing performance. For example, the ultrasonic welding filter adopts a new type of ultrasonic welding technology, with a pressure resistance of over 0.6MPa. At the same time, it adopts a new double-layer membrane design, which is particularly suitable for filtering large particles, high viscosity, and multi impurity materials. The edge wrapped filter adopts a double injection molding edge wrapping and ultrasonic welding double safety production process, which has a high pressure resistant structural design and can also ensure good sealing.
Other special requirements
Low adsorption design: For some trace analysis or high-sensitivity detection, such as mass spectrometry (MS) analysis, it is necessary to choose additive free filter membranes to avoid the precipitation of plasticizers and other substances, which may affect the analysis results.
Aseptic requirements: In some biological chromatography analyses or experiments that require sterile conditions, it is necessary to choose sterilized welded filters, such as products sterilized by gamma rays or ethylene oxide (EO), which are usually labeled as "sterile" on their packaging.
Compatibility with chromatographic system: Ensure that the interface of the welded filter matches well with the injection port, pipeline, etc. of the chromatographic system to avoid problems such as liquid leakage and poor connection.