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Mobile Phase Filtration Assembly: Example SOP for HPLC Labs

Last reviewed 29 Oct 2026 · 3 min read

Contents
  1. 1. Objective
  2. 2. Scope
  3. 3. Responsibility
  4. 4. Procedure
  5. 4.1 Preliminary checks
  6. 4.2 Filtering a mobile phase
  7. 4.3 After use
  8. 4.4 Maintenance
  9. 5. Records
  10. 6. Training and distribution
  11. Related reading
  12. Frequently asked questions
  13. Abbreviations
  14. References

In short: A vacuum filtration assembly removes particles from HPLC mobile phases and buffers so that columns and pumps are protected. This example SOP shows the checks, filtering steps, cleaning and records. Adapt it to your equipment and quality system.

1. Objective

This example SOP describes how to use the mobile phase filtration assembly in the Quality Control laboratory.

2. Scope

It applies to the vacuum-pump-driven glass filtration assembly used to filter mobile phases, buffers and diluents in the Quality Control laboratory.

3. Responsibility

  • Analyst: follows the SOP and records use in the equipment logbook.
  • Head of Quality Control (or designee): ensures implementation.

4. Procedure

4.1 Preliminary checks

  1. Check the assembly (funnel, receiver flask, clamp, membrane support) is clean, dry and free of cracks or chips.
  2. Check the vacuum pump is connected to the correct mains supply (per the equipment label) and the tubing is intact.
  3. Confirm the solvent or buffer to be filtered is labelled and within its preparation validity.

4.2 Filtering a mobile phase

  1. Rinse the funnel and receiver with purified water, followed by a small amount of the solvent to be filtered, to remove residues. Check there is no leakage at the joints.
  2. Fit a membrane filter that is chemically compatible with the liquid (for example nylon or PVDF for aqueous or mixed phases, PTFE for strongly organic or aggressive solvents), with the pore size required by the test method. A 0.45 µm membrane is commonly used (example in-house criterion; use the pore size in the method).
  3. Clamp the funnel, pour in the liquid and switch on the vacuum pump.
  4. Filter the whole volume. Switch off the pump when filtration is complete and release the vacuum before removing the funnel.
  5. Transfer the filtered mobile phase to a labelled, clean reservoir. Degas as the analytical method requires (sonication, vacuum or online degasser).
  6. Discard the used membrane. Never reuse membranes between different solutions.

4.3 After use

  1. Flush the assembly with purified water, then rinse with a suitable solvent if buffers or organic solvents were used.
  2. Switch off the vacuum pump and the mains, and do not leave the equipment switched on after use.
  3. Dry and store the assembly protected from dust.
  4. Record the use in the equipment logbook.

4.4 Maintenance

Unplug the equipment when not in use. Inspect glassware and tubing regularly, and replace damaged parts. Include the pump in the laboratory’s preventive maintenance schedule; written procedures for cleaning and maintaining equipment are expected under US FDA 21 CFR 211.67, and records of use under 21 CFR 211.182.

5. Records

Keep logbook entries with other laboratory records. Retain GMP records for at least 1 year after the expiry date of the respective product batch (EU GMP Part I, Chapter 4, §4.11; 21 CFR 211.180(a)), or longer if local law or the marketing authorisation requires.

6. Training and distribution

  • Trainer: Head of Quality Control. Trainees: QC chemists and section heads.
  • Controlled copies: Quality Assurance and Quality Control; a display copy may be kept in the wet laboratory area; original with Quality Assurance.

Frequently asked questions

Why filter the mobile phase? Particles can block frits, damage pump seals and shorten column life, and can cause baseline noise.

Do I need to filter HPLC-grade solvents? Buffers and aqueous phases should be filtered. Whether pure HPLC-grade organic solvents need filtering depends on the method and site practice.

Which membrane should I use? One compatible with the solvent and with the pore size stated in the method.

Abbreviations

HPLC: High Performance Liquid Chromatography; QC: Quality Control; SOP: Standard Operating Procedure.

References

  • US FDA, 21 CFR 211.67 (equipment cleaning and maintenance), 211.182 (equipment cleaning and use log), 211.180(a) (record retention).
  • European Commission, EudraLex Volume 4, Part I, Chapter 4 (Documentation), §4.11.
  • Equipment and membrane manufacturer’s instructions.

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