Membrane Filter Discs — Screen Filtration Membranes

Primary uses

• Retains particulate at a rated pore size at the membrane surface
• Provides a defined cut-off for methods that require one
• Supports gridded surface counting workflows in water microbiology programmes

Applications

• Water and effluent membrane filtration procedures
• Mobile phase and solution filtration in chromatography laboratories
• Particulate contamination testing in fluids and industrial cleanliness work
• Filtration steps inside standard food, feed and environmental methods

Advantages

• Gives a rated pore size, which is what methods requiring a defined cut-off are written around
• Surface retention makes gridded counting workflows possible in water testing programmes
• Available in several polymers, so the membrane can be matched to the solvent rather than the other way round

Limitations to consider

• Blinds quickly on heavily loaded samples, which usually means a pre-filter is needed rather than a different membrane
• Polymer choice affects adsorption, extractables and wetting behaviour, and the wrong choice can bias a trace-level result
• Rated pore size, chemical compatibility and any cleanliness declaration are manufacturer statements for the exact item
• Every numeric property — assay, purity, residual content, pore size, retention behaviour, ash content, extractables, thickness, capacity and dimensional tolerance — is a property of one manufactured item from one production line. Values are read from the manufacturer's own technical documentation for the exact item offered and confirmed at quotation, never quoted from a category page.
• A manufacturer declaration and a verified result are not the same thing. Declarations state what the manufacturer controls to; suitability inside your own method, matrix and instrument is established by your own verification. Where a result must stand up inside an accredited scope, plan that verification before the item enters routine use.

How to choose the right grade

• Take pore size from the method, then choose polymer from the solvent and analyte rather than from availability
• Match the diameter to the holder or funnel already in use, since changing the holder is the expensive part
• Where a gridded surface is needed for counting, confirm that explicitly rather than assuming it comes with the pore size
• Once a consumable is inside a validated method, changing it has a cost: the change has to be justified, trialled and documented. Continuity of the identical item usually matters more than unit price, so state the incumbent item and the property that must be matched when a second source is being qualified.
• Buyers frequently search using the catalogue name of a manufacturer they already use. Those are third-party trademarks belonging to their owners and are never used as an Allzone product identity. Where an equivalent is being considered, equivalence is assessed against the two sets of documentation and confirmed by the laboratory's own verification.
• Exact specification is confirmed against supplier documentation at quotation.

Typical grades

• Variant selection is made on the instrument, apparatus and test method rather than on a grade ladder
• Where a manufacturer operates distinct quality or cleanliness lines for the same item, the line is identified per offer
• Any declared property is read from the manufacturer documentation for the exact item offered, never assumed from a family name
• Regulatory listing, certification, food-contact status and any scheme approval belong to a specific item, facility and jurisdiction, and they change scope over time. State what your programme or customer requires at the enquiry stage so it is checked against current documentation for the offered item rather than assumed from a product name.
• These items are offered for industrial, food, feed, water, environmental and materials-testing work. Nothing here is offered, positioned or documented for medical, clinical, diagnostic or human-specimen use, and no such suitability is implied.