Selection of filter membrane for syringe filters to first consider is chemical compatibility, that is, whether the filter membrane is resistant to acids, alkalis, organic solvents, etc. For details, please refer to (attachment sheet) chemical compatibility table.
1. The pore size of the filter membrane for syringe filters:
* Pore size 0.45μm filter membrane: used for the mobile phase filtration of general samples, which can meet the general chromatographic requirements. For example: Chromatographic system for 3μm or larger particle size packing.
* Pore size 0.22μm membrane: it can remove the requirements of ultrafine particles in the sample and mobile phase. Such as: for chromatography systems with <3μm packing.
* Pore size 1-5μm filter membrane: commonly used in difficult to handle turbid solution, can be pre-filtered with 1-5μm filter membrane, and then use the corresponding filter membrane and then filter.
2. Characteristics of filtered samples for syringe filters:
A: Hydrophilic samples: Suitable for use with hydrophilic membranes, suitable for filtering water-based solutions. Such as: tap water, surface water, available filter membranes: water-based membrane (mixed cellulose ester), nylon membrane (polyamide).
B: For organic and inorganic compounds (alcohols, esters, oils), nylon films (polyamides) are suitable.
C: Protein solution sample: filter membrane suitable for low protein adsorption. That is, PVDF film.
D: Strong acid and alkali samples are suitable for hydrophobic PTFE (polytetrafluoroethylene membrane).
Selection of syringe filters:* Case: High-pressure polypropylene (PP) is resistant to high temperatures, does not leak, does not require membrane replacement and cleaning, and saves complicated and time-consuming preparation work. It is the first choice for filtering HPLC and GC small samples.
Characteristics and applications of several commonly used membranes:
1. Water-based membrane of syringe filters (mixed cellulose ester CA)Features: uniform pore size, high porosity, no medium shedding, thin texture, small resistance, fast filtration speed, low cost, but not resistant to organic solutions and strong acids and alkalis.
Applications: drinking water, surface water, well water, etc., sterilization filtration, analysis of particles and oil insolubles in solution, determination of water pollution index, filtration of particles and bacteria such as gas, oil, beverage, wine, etc. It is one of the most widely used filters in sample pretreatment filtration.
2. Nylon film (polyamide NYLON)Features: Good temperature resistance, can withstand 121 ° C, saturated steam autoclaving for 30 minutes, maximum working temperature of 60 ° C, good chemical stability, resistance to many organic and inorganic compounds and solvents such as dilute acid and alkali.
3. PVDF film (polyvinylidene fluoride)Features: The membrane has high mechanical strength, good tensile strength, good heat resistance and chemical stability, extremely low protein adsorption, and strong hydrophobicity.
4. PTFE (polytetrafluoroethylene)Features: Has a wide range of chemical compatibility, good temperature resistance, strong acid and alkali resistance, strong chemically corrosive solvents and oxidants.