Final Step Before Analyzing the Sample(Filtration): The Right Method
After a complex pre-treatment process,
many lab technicians might feel uncertain before analysis:
With so many filter membranes available,
which one should be chosen for filtration before proceeding with the analysis?
Nylon
Nylon Syringe Filters: These are widely used in various analytical processes. The hydrophilic nylon membrane is suitable for filtering both aqueous and organic solvents, such as in HPLC and GC sample preparation. Key features include high throughput, low extractables, and good mechanical strength. The excellent physical properties of nylon can meet the stringent requirements of various experimental conditions.
PES
PES Syringe Filters: These filters are specifically designed for laboratory filtration of cell culture media, serum, nutrient solutions, growth hormones, and other solutions requiring special treatment. PES syringe filters have been certified for particle retention, bacterial challenge, low extractable, and protein recovery.
Mixed Cellulose Ester （MCE）
Mixed Cellulose Ester (MCE) Syringe Filters: These filters have natural hydrophilicity and low protein binding, making them ideal for filtering aqueous solutions and biochemical analyses. They are particularly suitable for the preparation and filtration of biological samples and solutions.
PVDF
Polyvinylidene Fluoride (PVDF) Syringe Filters: These filters have a low protein binding rate, significantly lower than that of cellulose nitrate (CN), nylon, and polytetrafluoroethylene (PTFE) filters. They are compatible with a wide range of organic solvents, making them highly versatile. PVDF filters also exhibit excellent oxidation resistance and heat resistance, making them suitable for HPLC/GC and the preparation and filtration of biological samples.
PP
Polypropylene (PP) Syringe Filters: The PP membrane is a naturally hydrophobic filtration medium characterized by high throughput and high dirt-holding capacity. These filters are suitable for routine filtration of organic solvents with high particulate content.
PTFE
Polytetrafluoroethylene (PTFE) Syringe Filters: These filters are used for filtering highly chemically corrosive organic solvents, aqueous solutions, and gases. They have exceptional chemical compatibility and can withstand most strong acid and alkali solutions.
GF
Glass Fiber (GF) Syringe Filters: These filters are characterized by high throughput and high dirt-holding capacity. They are suitable for routine filtration of solutions with high particulate content and viscosity. Additionally, they can be used as pre-filters for difficult-to-filter solutions.
CA
Cellulose Acetate (CA) Syringe Filters: These filters are suitable for filtering aqueous solutions. Cellulose acetate combines features such as high flow rates, thermal stability, and low adsorption. The 0.22μm pore size cellulose acetate membrane is perfectly suited for clarification or sterilization filtration of aqueous solutions and other liquids.
The impurities present in samples and solvents not only cause damage to injectors, chromatographic columns, and pumps but also have a significant impact on analytical results. Therefore, pre-filtering of samples before injection can not only prevent pump damage and blockages in injectors and chromatographic columns but also greatly improve analytical results, thereby enhancing sensitivity and accuracy.
How to Choose the Right Filter Membrane
The selection of an appropriate filter membrane primarily depends on the chemical compatibility between the membrane and the liquid being filtered (aqueous solution, organic solvent, or amphiprotic solution).
• Nylon membranes and hydrophilic PTFE membranes: Due to their broad chemical compatibility, they are mainly used in HPLC-related filtration. They can be used for filtering both aqueous and organic solutions.
• Hydrophilic PVDF and PES membranes: Due to their low protein adsorption characteristics, they are primarily used for filtering protein solutions and can also be used for gentle organic solvent filtration.
• Hydrophobic PTFE membranes: Due to their extensive chemical compatibility, they are mainly used for filtering organic solvents. MCE membranes are mainly used for filtering and analyzing aqueous solutions.
Today's Interactive Topics
Please list specific situations in daily experiments where you're unsure which filter to use! Feel free to ask questions!
Share instances you've discovered where syringe filters are particularly picky in experiments.