Ideal Filter Size Retention
Estimate weighted size-exclusion fractions in an ideal rigid-pore model; actual membrane retention requires validation.
Description
Calculate weighted passing and retained fractions under a rigid-pore size cutoff, retaining particles exactly equal to the pore diameter.
Size exclusion describes a geometric idea: a particle larger than an opening cannot pass through it as a rigid object. Actual virus filtration depends on membrane pore distributions and the measurement conditions, so a single nominal diameter is an idealization rather than a verified retention specification.1
A size distribution can be represented by diameter classes with nonnegative weights. Here weights represent relative particle abundance; they need not already sum to one. The model counts a class as passing only when its diameter is strictly smaller than the supplied pore diameter.
Ideal Filter Size Retention normalizes the passing weight by total weight and returns its complement as retained fraction. It is a deterministic size-screening model without a membrane-performance or viral-clearance calculation.
When to explore an ideal size-exclusion scenario
Use the tool for a transparent geometric comparison with a supplied particle-size distribution. Keep the meaning of the weights explicit, especially if the original instrument reports intensity or mass rather than particle abundance.
- Compare ideal fractions at different pore diameters.
- Check how particle-class weights affect the result.
- Demonstrate the exact-diameter boundary in a simple model.
How to enter diameter classes and weight the cutoff
- Enter nonempty positive Virion diameters nm and aligned nonnegative Particle weights.
- Ensure at least one weight is positive. Enter positive Pore diameter nm in nanometers.
- Run the model and read Ideal passing fraction and Ideal retained fraction.
- Interpret the outputs under this strict geometric rule before considering measured filter performance.
passing = sum(weights_i where diameter_i < poreDiameter)/sum(weights_i); retained = 1 − passing The implementation sums weights directly. Equal-size particles belong to the retained category, and zero-weight classes do not affect either fraction.
{
"input": {
"virionDiametersNm": [
20,
50,
100
],
"particleWeights": [
1,
2,
1
],
"poreDiameterNm": 50
},
"output": {
"idealPassingFraction": 0.25,
"idealRetainedFraction": 0.75
}
}All classes smaller than the pore give passing fraction 1; none smaller gives 0. Diameter order is irrelevant. Empty/misaligned lists, all-zero weights, negative weights, nonpositive diameters, or nonfinite values produce errors.
Limitations and interpretation
- No pore-size distribution, adsorption, particle deformation, aggregation, fouling, pressure, or membrane-defect model is included.
- The fractions are weighted model outputs, not demonstrated log-reduction values or evidence of sterilization.
- The input weights determine the represented population. Intensity or mass weights do not automatically yield particle-number fractions.
- No uncertainty estimate or measured filter validation is performed.
Alternative or Complementary methods
A sphere-volume calculation helps illustrate how size and volume differ but does not validate retention. Infectious-to-physical ratios summarize another property of particles and require independent measurements rather than a size cutoff.
References
-
Measurement of pore size distribution and prediction of membrane filter virus retention using liquid–liquid porometry — Journal of Membrane Science
Similar or alternative tools
- Sphere Volume Calculator
Calculate the volume of an ideal sphere from a radius in a consistent length unit.
- Infectious Physical Particle Ratio
Compare measured PFU and particle abundance without predicting filtration.