What Are Steps to Choose a Syringe Filter?

In general, there are two steps to choose a suitable syringe filter, step 1 to choose the filter membranes and step 2 to choose the syringe filter. Several key parameters of filter membrane and syringe filter:

1. Material: such as nylon, polyethersulfone, polytetrafluoroethylene
2. Aperture: such as 0.22μm, 0.45μm
3. Diameter: such as 13mm, 25mm

(1) The choice of filter membrane

First of all, chemical compatibility should be considered, that is, whether the filter membrane is resistant to acids, alkalis, organic solvents, etc.

1. Characteristics of filtered samples

A: Hydrophilic sample: It is suitable to use a hydrophilic membrane, which is suitable for filtering water-based solutions, such as tap water and surface water, the available filter membranes are water-based membranes (mixed cellulose esters), nylon membranes (polyamides).
B: Nylon membrane (polyamide) is suitable for samples of organic and inorganic compounds (alcohols, esters, oils).
C: Protein solution sample: filter membrane suitable for low protein adsorption, namely PVDF membrane.
D:Strong acid and strong base samples are suitable for hydrophobic PTFE (polytetrafluoroethylene membrane).

2. The pore size of the filter membrane

Pore size 0.45μm filter membrane: it can meet general requirements, such as chromatography system for 3μm or larger particle size packing.
Pore size 0.22μm filter membrane: It can remove extremely fine particles in the sample and mobile phase. Such as: chromatography systems for <3μm particles.

Pore size 1-5μm filter membrane: commonly used for difficult to handle turbid solutions, it can be pre-filtered with a 1-5μm filter membrane, and then filtered with the corresponding filter membrane.

3. Diameter of filter membrane

The commonly used microporous filter membrane is generally a disc filter membrane, such as a 25mm disc microporous filter membrane, which can be used with a syringe filter connected to a syringe. 47mm disc microporous membrane, can use membrane filter, Buchner funnel, pressure vessel, etc. with vacuum pump and pressure pump. There are also larger diameter microporous membranes, which also require corresponding clamps and pressure fits. Other microporous membranes can be selected according to needs.

(2) The choice of syringe filter

1. Shell

High-pressure polypropylene (PP) is resistant to high temperature, does not leak, does not require membrane replacement and cleaning, saves complicated and time-consuming preparations, and is a small sample product for filtration of HPLC and GC.

2. Specification

Two types of Φ13μm and Φ25μm are commonly used, that is, Φ13μm is selected for the sample volume of 2-10ml, and Φ25μm is selected for the sample volume of 10-100ml.

3. Characteristics and applications of several commonly used syringe filters

A: mixed cellulose ester syringe filter Features: uniform pore size, high porosity, no media shedding, thin texture, low resistance, fast filtration, low cost, but not resistant to organic solutions and strong acids and alkalis.
Application: drinking, surface water and well water, etc., sterilization filtration, analysis of particles and oil insolubles in solution, filtration of particles and bacteria such as gas, oil, beverage, wine, etc.
B: Nylon syringe filter
Features: good temperature resistance, good chemical stability, can withstand a variety of organic and inorganic compounds and solvents.
Application: Suitable for water filtration in electronics, semiconductor industry, filtration of tissue culture medium, liquid medicine, beverage, high-purity chemicals, and mobile phase of organic solution.
C. PVDF syringe filter
Features: The membrane has high mechanical strength, good tensile strength, good heat resistance and chemical stability, very low protein adsorption, and strong hydrophobicity.
Application: Gas and steam filtration, high temperature liquid filtration, sterilization filtration of tissue culture medium, solvent and chemical raw material purification filtration.
D. PTFE syringe filter
Features: It has a wide range of chemical compatibility, good temperature resistance, strong acid and alkali resistance, strong chemical corrosive solvents and oxidants.
Application: It can filter almost all organic solutions in the fields of chemical industry, medicine, environmental protection, electronics, food, energy and so on.