How to Choose the Syringe Filters and Membranes?
In many experiments, many samples and solvents need to be filtered in advance to remove particulate contaminants and protect the instrument. Syringe filters and filter membranes can be used in HPLC analysis and IC analysis. It is a very important step to filter sample solutions in the sample pretreatment process.
(1) Composition of syringe filter
The syringe filter consists of a graduated needle tube and a filter head. The filter head contains filter membranes with different characteristics. Filter membranes with different performances can be selected according to experimental requirements.
(2) Factors to consider when choosing a syringe filter
1. Consider the effective filtration area (EFA)
Particles in the fluid affect the life of the filter. When the particles are removed by the filter, they also block the voids and reduce the usable part of the filter. Compared with "clean" fluids, fluids loaded with particles are more likely to clog the filter, and increasing the EFA (effective filter area) can extend the life of the filter.
2. Consider the aperture size
The pore size of the syringe filter membrane has two kinds of 0.22μm and 0.45μm, of which 0.22μm can remove very fine particles in samples and mobile phases, which can meet the requirements of 99.99% sterilization stipulated by GMP or Pharmacopoeia; 0.45μm can filter. In addition to most bacteria and microorganisms, it can meet the general chromatographic requirements and filtration requirements of conventional samples and mobile phase.
3μm or larger particles syringe filters or membranes can be used in chromatographic column systems; 0.22μm membranes are suggested for chromatographic systems involving microbial growth or using less than 3μm fillers.
Also, choose the appropriate pore size according to the analytical instrument. UV/V spectrophotometer may only need 1um filter; HPLC analysis may need 0.45um filter, UHPLC will need 0.2um filter, due to the volume, filler and gap size, the pore size of the filter material depends on the smallest particle diameter. These particles will be effectively intercepted by the filter of rated pore size.
(3) Several common filter membrane characteristics and applications
1. Water-based membrane (mixed cellulose ester CN-CA)
Features: cost effective, low resistance, fast speed, uniform pore size
Applications: water sterilization filtration, solution particles and oil insolubles analysis, particles and bacteria filtration and water pollution index determination and so on. It is one of the most widely used membranes in sample pretreatment filtration.
2. Nylon membrane
Features: Nylon membrane syringe filter
has good temperature resistance, 121°C resistance, saturated steam autoclave sterilization for 30 minutes, maximum working temperature 60°C, good chemical stability, resistance to various organic and inorganic compounds, solvents such as dilute acids and alkalis.
Application: water filtration, high-purity chemicals filtration.
3. PVDF membrane
Features: Membrane of PVDF syringe filter
have Great tensile strength, very low protein adsorption, high mechanical strength, excellent chemical stability and good heat resistance.
Application: Sterilization filtration, purification filtration for chemical raw material, steam/gas filtration and so on.
4. PTFE membrane
Features: Membrane of PTFE syringe filter
have strong chemical corrosion and resistant to strong acid, strong base,and oxidant, great temperature resistance.
Application: Chemical, pharmaceutical, environmental protection, electronics, food, energy and other fields, can filter almost all organic solutions.