Descrizione
At 0.45 Microns, the World Separates. Bacteria cannot pass. Suspended solids are arrested. Dissolved salts flow through. This is the threshold where laboratory filtration ceases to be a procedural step and becomes a chemical statement — and it all depends on the membrane. JOANLAB's microporous filtration membrane is not filter paper. It is a precision-engineered polymer barrier with a controlled pore distribution that passes what must pass and retains what must not.
Manufactured from mixed cellulose esters (MCE) with a nominal pore size of 0.45μm, this membrane is the workhorse specification for water quality analysis, microbiological testing, particulate counting, and general laboratory clarification. The 47mm and 50mm diameter formats fit standard vacuum filtration manifolds and stainless steel filter holders without trimming. Bubble point and flow rate specifications are batch-tested, not estimated — each lot ships with a certificate of conformance, not a generic datasheet that may or may not apply to the membranes in your hand.
What separates a laboratory-grade membrane from "filter paper sold by a general supplier" is pore-size uniformity. MCE membranes produced via controlled phase-inversion casting achieve a coefficient of variation under 8% across the active surface — meaning your 0.45μm specification is a guarantee, not an average. This matters when you are validating a water-purification protocol, enumerating coliform bacteria, or preparing samples for HPLC injection. A single oversized pore in a budget membrane can pass a contaminant that invalidates your entire batch result, and you will never know which data point it ruined.
Filtration is not about what you can see. It is about what you can prove was removed.
Key Features
- ✦ 0.45μm Nominal Pore Size — The standard specification for water microbiology, particulate analysis, and general lab clarification
- ✦ Mixed Cellulose Ester (MCE) Composition — Low protein binding, high flow rate, and uniform pore distribution via phase-inversion casting
- ✦ Batch-Tested Quality Control — Each lot is tested for bubble point, flow rate, and extractable contaminants; ships with batch-specific conformance data
- ✦ Standard Diameters (47mm/50mm) — Fits all common vacuum filtration manifolds, stainless steel holders, and syringe filter housings
- ✦ COV ≤8% Pore Uniformity — Tight pore-size distribution eliminates the oversized-pore outliers that compromise budget membranes
- ✦ JOANLAB Brand Quality — A recognized laboratory consumables manufacturer with full documentation traceability
Technical Specifications
- Brand: JOANLAB
- Membrane Material: Mixed Cellulose Esters (MCE)
- Pore Size: 0.45μm (nominal)
- Diameter: Available in 47mm and 50mm
- Thickness: 120–160μm (typical for MCE)
- Pore Uniformity: COV ≤8% (batch-validated)
- Sterilization: Autoclavable at 121°C (non-sterile packaging)
- Wettability: Hydrophilic — no pre-wetting required for aqueous solutions
- Packaging: Individually interleaved with separator paper, boxed
Application Scenarios
Water quality laboratories use these membranes for total coliform and E. coli enumeration via membrane filtration (MF) technique per Standard Methods 9222. Pharmaceutical QC departments employ them for particulate matter analysis in injectable solutions. Environmental monitoring stations rely on 0.45μm MCE for suspended solids determination in surface water and wastewater effluent. University teaching labs stock them for microbiology practicals. Food and beverage microbiology labs use them for spoilage organism detection in liquid products. The membranes are also suitable for HPLC mobile phase preparation, protein solution clarification, and air monitoring via cassette sampling.
Frequently Asked Questions
Q: Are these membranes pre-sterilized?
A: No, they are shipped non-sterile. For microbiological work requiring sterility, autoclave at 121°C for 15 minutes. MCE membranes withstand autoclaving without pore-size alteration when properly supported and not over-pressurized. Some labs prefer ethylene oxide sterilization for high-throughput workflows.
Q: What is the difference between 0.45μm and 0.22μm membranes?
A: 0.45μm is sufficient for total coliform testing and general clarification — it retains most bacteria. 0.22μm is required for sterilization-grade filtration (retains all bacteria including small species like Brevundimonas diminuta). If you are preparing sterile solutions for cell culture or injectables, use 0.22μm. For water quality analysis per EPA methods, 0.45μm is the specified pore size.
Q: Do these membranes require a specific filter holder?
A: They fit any standard 47mm or 50mm vacuum filtration assembly — glass microanalysis holders, stainless steel pressure holders, and polysulfone filter funnels all accept these diameters. Ensure the fritted support is flat and undamaged to prevent membrane rupture under vacuum.
Q: Why does pore uniformity (COV ≤8%) matter?
A: A membrane with a "0.45μm nominal" rating but poor uniformity can have individual pores exceeding 1μm. During filtration, bacteria or particulates pass through these oversized pores, yielding false-negative results. In water quality testing, this means declaring water safe when it is not. JOANLAB's phase-inversion process controls this variation to under 8%, which is considered research-grade.
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