Filter Material Compatibility and Non-Specific Adsorption Risk Assessment

Document type	Risk Assessment
Topic area	Drug Product
Level	Advanced
Updated	September 2026

This is a ready-to-use risk assessment for deciding whether a sterilizing-grade filter’s membrane chemistry is likely to adsorb a meaningful amount of protein, polysorbate, or another formulation component out of the product, and whether a validated pre-flush or a different membrane material is warranted. Replace every <<FILL: ...>> placeholder with your own specifics and route it through your normal document control, review, and approval. A worked filled specimen follows. Verify each cited reference against the current source before you rely on it.

Document control header

Field	Entry
Document title	Filter Compatibility and Adsorption Risk Assessment for `<<FILL: product / process step>>`
Document number	`<<FILL: e.g. RA-FLT-014>>`
Version	`<<FILL>>`
Effective date	`<<FILL>>`
Filter / membrane material / manufacturer / part number	`<<FILL>>`
Document owner	`<<FILL: e.g. Filter Validation Lead>>`

1. Purpose

This assessment evaluates the risk of non-specific adsorption of active ingredient or a critical excipient to the sterilizing filter membrane during final filtration, and documents whether the manufacturer’s stated flux and retention performance alone are sufficient or whether a compatibility study and a validated pre-flush are required.

2. Scope

Dimension	Decision
Product / process step assessed	`<<FILL>>`
Formulation concentration at this step	`<<FILL>>`
Surfactant present, type and target concentration	`<<FILL: e.g. polysorbate 80, 0.02% w/v, or none>>`
Membrane material under assessment	`<<FILL: PES, PVDF, nylon, other>>`
Out of scope	`<<FILL: e.g. bacterial retention and integrity testing, covered under separate protocols>>`

3. Responsibilities

Role	Responsibility
Filter validation lead	Facilitates the assessment, owns the conclusion and any pre-flush validation
Formulation / process development	Supplies concentration, surfactant, and excipient data, and confirms which components carry the highest adsorption concern
Analytical lead	Runs or oversees the concentration and potency comparison between pre-flush and steady-state filtrate
Quality Assurance	Approves the conclusion and, where a pre-flush is required, the validated volume and the batch record language implementing it

4. Method and risk factors

Score each factor below as present or absent for the specific formulation and process step. More than one factor present shifts the assessment from “monitor” toward “test,” and any factor present at a protein concentration below roughly 10 mg/mL, or for a surfactant controlled to a narrow specification range, is enough on its own to warrant a small-scale compatibility study before the membrane material is locked in.

Risk factor	Present?	Notes
Active ingredient concentration below approximately 10 mg/mL	`<<FILL: Yes/No>>`	`<<FILL>>`
Polysorbate or another surfactant present at a tightly controlled specification	`<<FILL: Yes/No>>`	`<<FILL>>`
Membrane material is nylon or another material without published low-adsorption data for this formulation class	`<<FILL: Yes/No>>`	`<<FILL>>`
No prior compatibility data exists for this exact membrane and formulation combination	`<<FILL: Yes/No>>`	`<<FILL>>`
Product is high-value or supply-constrained, making an undetected loss costly beyond the immediate batch	`<<FILL: Yes/No>>`	`<<FILL>>`

5. Small-scale compatibility study summary

Field	Entry
Study design	`<<FILL: e.g. filtrate sampled at increasing L/m2 throughput, compared to a steady-state sample>>`
Concentration / potency method used	`<<FILL>>`
Result: point at which filtrate concentration returns to within specification	`<<FILL: X L/m2>>`
Result: protein or active ingredient loss observed	`<<FILL: Yes/No, with data>>`
Result: surfactant loss observed	`<<FILL: Yes/No, with data>>`

6. Conclusion and pre-flush basis

Field	Entry
Adsorption risk to active ingredient or excipient	`<<FILL: Low / Moderate / Significant>>`
Pre-flush required?	`<<FILL: Yes/No>>`
Validated pre-flush volume, if required	`<<FILL: X L/m2, with margin above the study result>>`
Pre-flush fluid	`<<FILL: representative placebo, buffer, or other qualified fluid>>`
Point in the batch sequence where in-process sampling begins	`<<FILL>>`
Basis for decision	`<<FILL>>`

7. References

ASTM F838, Standard Test Method for Determining Bacterial Retention of Membrane Filters Utilized for Liquid Filtration. PDA Technical Report No. 26, Sterilizing Filtration of Liquids. BioPhorum Extractables Protocol (current edition), for the related but distinct extractables and leachables assessment.

Confirm the current version of each reference before issue.

8. Revision history

Version	Date	Author	Summary of change
`<<FILL: 1.0>>`	`<<FILL>>`	`<<FILL>>`	Initial issue.

9. Approvals

Role	Name	Signature	Date
Author (Filter Validation Lead)	`<<FILL>>`
Reviewer (Formulation / Process Dev)	`<<FILL>>`
Reviewer (Analytical)	`<<FILL>>`
Approver (QA)	`<<FILL>>`

Filled specimen

Extract for an example monoclonal antibody drug product formulated at 5 mg/mL with polysorbate 80 at 0.02% w/v, filtered through a 0.2 micron hydrophilic PVDF sterilizing filter before fill. Company and product are illustrative.

Risk factor	Present?
Active ingredient concentration below approximately 10 mg/mL	Yes, 5 mg/mL
Polysorbate or another surfactant present at a tightly controlled specification	Yes, polysorbate 80 at 0.02% w/v, specification plus or minus 0.005%
Membrane material without published low-adsorption data for this formulation class	No, PVDF has published data, but shows measurable adsorption at this concentration range
No prior compatibility data for this exact membrane/formulation combination	Yes
Product high-value or supply-constrained	Yes

Small-scale study: filtrate sampled at 5, 15, 30, and 60 L/m2 throughput, compared to a steady-state sample at 150 L/m2. Polysorbate concentration in the first 5 L/m2 sample measured 78% of target, recovering to within specification (95 to 105% of target) by 20 L/m2. Protein concentration and potency showed no significant deviation from target at any sampling point. Conclusion: moderate adsorption risk specific to polysorbate, low risk to protein. Validated pre-flush volume set at 30 L/m2 with margin above the 20 L/m2 recovery point, run with a placebo formulation matching the product’s buffer and polysorbate composition without active ingredient. Batch record specifies the 30 L/m2 pre-flush, discarded to waste, before in-process product sampling begins at the filter outlet.

Common inspection findings this risk assessment prevents

A filter selected on flux and pressure-drop performance alone, with no documented check of adsorption behavior against the actual formulation.
A pre-flush performed inconsistently or by informal practice, with no validated volume or batch record language specifying it.
Polysorbate loss discovered only as an out-of-specification result on a finished batch, with no upstream compatibility data to explain it.
A low-concentration presentation of an existing product filtered through the same membrane validated at a higher concentration, with no reassessment of adsorption risk at the new concentration.

How to adapt this risk assessment

Set your document number, product, and membrane identifiers in the header.
Score every factor in section 4 honestly; a single “Yes” at low concentration or a tightly controlled surfactant specification is enough to warrant the study in section 5.
Size the pre-flush volume in section 6 with real margin above the point where the study shows recovery, not at the exact recovery point.
Route the validated pre-flush volume and fluid into the actual batch record language, not just this assessment, so manufacturing executes it consistently.
Confirm every reference in section 7 against the current published version before issue.