A syringe filter is a wheel shaped filter. It contains a plastic body with a membrane used for purification of contaminants. There is a universal Luer lock present for versatility. These are mainly used in removal of microorganisms and particles from liquid or gases. They contain a syringe coupled with filter membrane. They are available in various pore sizes and with many hydrophilic or hydrophobic membrane materials. Syringe filters are used in HPLC Sample preparation, Routine QC analysis, food analysis, environmental sample analysis, bio fuel analysis and removal of protein precipitation.
They have applications in many industries like Pharmaceutical, Food and Beverage, Environment and general laboratory. In HPLC they remove the particles from the sample before it enters the column. This increases the accuracy of results and life span of the column.
These filters can have a membrane of Polypropylene, Nylon, Mixed cellulose, PTFE and PES. Filter selection depends on the nature of the sample used. Aqueous samples are purified with hydrophilic membranes like nylon syringe filters or mixed cellulose syringe filters. The mixed cellulose ester membrane is ideal for sensitive biological samples. They mainly constitute cellulose nitrate and cellulose acetate.
For non polar solvents hydrophobic membranes are used such as Polytetrafluoroethylene (PTFE). It is a chemically resistant polymer and can be used for highly corrosive and aggressive solvents. Acids and bases are purified through them because of their high stability. They also have high thermal stability. PTFE membranes can also be used to prevent moisture in air vents.
Protein samples are purified using low protein binding filters polyvinylidene difluoride (PVDF) or Polyethersulfone (PES) membranes. They are hydrophilic in nature. For inorganic samples used in ion chromatography PES membranes are preferable. Maximum sample can be recovered by them. They are available in both forms, sterile and non sterile. PVDF membranes bind very low protein in comparison to other membranes and have a broad chemical compatibility.
Propylene membranes are hydrophobic and can be used with aqueous and organic solvents. Pore size and diameter should be considered while choosing membrane of these filters.
Glass fiber syringe filters are used for samples which are hard to purify such as media used in tissue culture or samples with large particles. They can easily sieve viscous substances. They are also used in monitoring of air pollution and the presence of oil and smoke in the air. They have high flow rates and high dirt holding capacity.