SOP for Swab and Rinse Sampling After Equipment Cleaning

In short: This example SOP describes how IPQA staff collect swab and rinse samples from cleaned manufacturing equipment so that QC can check for product, cleaning-agent or microbial residue. It is a template: adapt the volumes, areas, solvents and limits to your own validated cleaning and analytical methods.

Swab and rinse samples are the two usual ways to prove that equipment is clean enough for the next product. Swabbing tests a defined, hard-to-clean spot directly; rinsing tests a large or inaccessible surface in one go. Both only mean something if the way you sample is controlled and the recovery of residue from the surface has been shown.

What the regulators expect

• EU GMP Annex 15 (2015), section 10, says sampling is done by swabbing and/or rinsing or by other means suited to the equipment, that the sampling materials and method must not influence the result, and that recovery must be shown for every product-contact material sampled with every sampling method used (10.12). The protocol must name the locations to be sampled and why they were chosen (10.11).
• Annex 15 also says a visual check for cleanliness is an important criterion but is not normally acceptable on its own, and that repeated cleaning and retesting until a result passes is not an acceptable approach (10.2).
• The US FDA Guide to Inspections of Validation of Cleaning Processes (July 1993) calls direct surface (swab) sampling the most desirable method, notes that rinse sampling suits large areas and equipment that cannot be routinely dismantled, and expects the firm to challenge the sampling method by showing how much residue can actually be recovered.

Example SOP

This example SOP is an illustration. Values marked “example in-house criterion” are site choices, not regulatory requirements.

1. Objective

To lay down a procedure for collecting swab and rinse samples from cleaned equipment and product-contact surfaces during manufacturing.

2. Scope

Applies to swab and rinse sampling of equipment at the manufacturing facility, for cleaning validation, cleaning verification and routine monitoring.

3. Responsibility

• IPQA officer (or designee): receives the sampling request, collects the sample at the specified location, labels it and sends it to QC or Microbiology.
• Production: raises the request, completes cleaning and visual inspection before calling IPQA.
• QC / Microbiology officer: receives the request, analyses the sample and reports the result to QA.
• Head QA: approves the SOP, decides on investigations and on release of the equipment.

4. Procedure

4.1 Before sampling

1. Production completes cleaning as per the equipment cleaning SOP and checks the equipment visually.
2. Production fills in the rinse/swab analysis request slip (Annexure I) and gives it to IPQA.
3. IPQA collects the sampling kit and confirms the sampling locations against the approved cleaning validation protocol or sampling plan. Locations are fixed in advance and not chosen at the time of sampling.
4. IPQA wears clean gloves and changes them between sampling points.

4.2 Rinse sampling

1. Rinse sampling is done only after the equipment has passed visual inspection.
2. Use the final rinse solvent defined in the cleaning procedure. Example in-house criterion: purified water.
3. Rinse the surface in the defined way and collect the rinse from each identified sampling point in a clean, labelled container. Example in-house criterion: 100 mL per sampling point.
4. Rinse sampling covers large surface areas and systems that cannot be dismantled routinely. Its limit is that a localised residue can be averaged out, so use it together with swabs where the risk justifies it.

4.3 Swab sampling

1. Use the swab type and the solvent defined in the validated method. Example in-house criterion: nylon swab moistened with 10 mL purified water.
2. Mark out the surface to be swabbed, using a template where possible. Example in-house criterion: 25.8064 cm² (4 square inches).
3. Wipe the whole marked area with firm, even strokes in a zig-zag pattern in one direction, turn the swab and repeat at right angles, then wipe the edges. Use the same technique each time, because the recovery study only supports the technique that was validated.
4. Place the swab in the extraction solvent or transport tube, label it with the equipment ID, location, date, time and sampler, and close it.
5. Send the samples with the request slip to QC (chemical residue) or Microbiology (bioburden), within the time allowed by the validated method.

4.4 Analysis and result

1. QC or Microbiology analyses the sample and reports the result to IPQA and QA.
2. Results are calculated against the surface area or rinse volume sampled, and corrected for the recovery factor established during method validation.
3. If a result fails, an investigation (OOS) is started to find the root cause.
4. If the cause is inadequate cleaning, the equipment is cleaned again and re-sampled. The equipment is released only after QA has evaluated the re-cleaning. Do not simply repeat sampling until a passing result appears.
5. Raw data, request slips and reports are kept with the batch or validation 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.

5. Recovery studies (why they matter)

A swab or rinse result is a minimum value: some residue always stays behind on the surface or on the swab. Spike the surface with a known amount of residue, sample it exactly as in this SOP, and calculate the percentage recovered. Do this for each product-contact material (for example stainless steel, glass, silicone, PTFE) and each sampling method. A low or inconsistent recovery means the swab, solvent or technique needs to change before the method can be used for validation.

6. Training

• Trainer: Head QA or designee.
• Trainees: IPQA, production, packaging, QC, Microbiology and stores staff who handle or request cleaning samples.

7. Distribution

Controlled copies to QA, Production, QC, Microbiology, Warehouse/Stores and Packing; the original stays with QA.

8. Annexure

Annexure I: Rinse and swab analysis request slip.

9. Abbreviations

IPQA: in-process quality assurance. OOS: out of specification. QC: quality control. QA: quality assurance.

10. Revision history

Frequently asked questions

Is a rinse sample or a swab better?

Neither is better in every case. Swabs target worst-case spots and can remove dried residue. Rinse samples reach inaccessible parts. Many sites use both, as the FDA inspection guide suggests.

Can I judge cleaning by looking at the equipment?

Visual cleanliness is a necessary first check, but Annex 15 says it is generally not acceptable as the only criterion for cleaning validation.

Why must the sampling points be fixed in advance?

So the result represents the hardest-to-clean locations and not conveniently clean ones. Annex 15 (10.11) expects the protocol to give the locations and the reason for choosing them.

What if recovery is poor?

Change the swab material, solvent or technique and repeat the recovery study. Do not apply a low recovery figure as a correction unless your protocol justifies it.

See also: SOP on cleaning validation, Principles of cleaning validation and Cleaning validation protocol format.

References

• European Commission, EudraLex Volume 4, EU GMP Annex 15: Qualification and Validation (2015), section 10 Cleaning Validation, 10.2, 10.11 and 10.12 (Commission text dated 30 March 2015, in operation from 1 October 2015, health.ec.europa.eu).
• US FDA, Guide to Inspections of Validation of Cleaning Processes (July 1993), fda.gov.
• European Commission, EudraLex Volume 4, EU GMP Part I Chapter 4: Documentation, 4.11 (record retention).
• 21 CFR 211.180(a), General requirements for records, ecfr.gov.