The main purpose of needle filters is to filter liquids and remove particles, sediments, microorganisms, etc. They are widely used in biology, chemistry, environmental science, medicine and pharmaceuticals. This filter is widely welcomed for its excellent filtering effect, convenience and efficiency. However, it is not easy to choose the right needle filter. It is necessary to understand the characteristics of various filter membranes and other related factors. This article will discuss the uses of needle filters, the characteristics of filter membranes of different materials, and how to make a suitable choice.
Aperture of filter membrane
Aperture 0.45μm filter membrane: used for conventional sample mobile phase filtration, can meet general chromatographic requirements.
Aperture 0.22μm filter membrane: can remove extremely fine particles in samples and mobile phases and remove microorganisms.
Diameter of filter membrane
Generally, the commonly used filter membrane diameters are Φ13μm and Φ25μm. Φ13μm is used for sample volume 0-10ml, and Φ25μm is used for sample volume 10-100ml.
Characteristics and applications of several commonly used filter membranes
01
Polyethersulfone (PES)
Features: hydrophilic filter membrane with high flow rate, low dissolution, good strength, no adsorption of proteins and extracts, no pollution to samples.
Application: designed for biochemistry, testing, pharmaceutical and sterilization filtration.
02
Mixed cellulose ester (MCE)
Features: uniform pore size, high porosity, no medium shedding, thin texture, low resistance, fast filtration rate, minimal adsorption, low price cost, but not resistant to organic solutions and strong acid and alkali solutions.
Application: Filtration of aqueous solutions or sterilization of heat-sensitive preparations.
03
Nylon membrane (Nylon)
Features: good temperature resistance, can withstand 121℃ saturated steam autoclave sterilization for 30 minutes, good chemical stability, can withstand dilute acids, dilute alkalis, alcohols, esters, oils, hydrocarbons, halogenated hydrocarbons and organic oxides and other organic and inorganic compounds.
Application: Filtration of aqueous solutions and organic mobile phases.
04
Polytetrafluoroethylene (PTFE)
Features: The widest chemical compatibility, can tolerate organic solvents such as DMSO, THF, DMF, dichloromethane, chloroform, etc.
Application: Filtration of all organic solutions and strong acids and alkalis, especially strong solvents that other filter membranes cannot tolerate.
05
Polyvinylidene fluoride membrane (PVDF)
Features: The membrane has high mechanical strength, good heat resistance and chemical stability, low protein adsorption rate; it has strong negative electrostatic properties and hydrophobicity; but it cannot tolerate acetone, dichloromethane, chloroform, DMSO, etc.
Application: Hydrophobic PVDF membrane is mainly used for gas and steam filtration, and high-temperature liquid filtration. Hydrophilic PVDF membrane is mainly used for tissue culture medium, aseptic treatment of solutions, high-temperature liquid filtration, etc.
Summary
A: Hydrophilic samples: It is suitable to use hydrophilic membranes, which are suitable for filtering solutions with water as the matrix. For example, tap water and surface water, the filter membranes can be water system membranes (MCE) and nylon membranes (Nylon).
B: Samples of organic and inorganic compounds (alcohols, esters, oils): Nylon membrane is suitable.
C: Samples of protein solutions: PVDF membrane is suitable for low protein adsorption.
D: Samples of strong organic solvents: Hydrophobic PTFE is suitable.
E: Ion chromatography: PES membrane is generally considered to be more suitable for filtering solutions with low inorganic ions.
Post time: Jul-09-2024