SOP for Preparation of Disinfectant Solution (Example)

In short: This is an illustrative example SOP for preparing and using disinfectant solutions in a manufacturing area. All concentrations, quantities, rotation periods and expiry times shown are example in-house criteria; your own validated values and the manufacturer’s label must replace them. It is meant for production, QA and microbiology staff.

What regulators expect

Neither the regulations nor the guidelines fix a “standard” concentration or contact time. They expect a written, validated programme. EU GMP Annex 1 (2022 revision) says, in the section on disinfection of cleanrooms (clauses 4.33 to 4.36):

• cleaning and disinfection should follow a written programme, surfaces should be cleaned before disinfection so the disinfectant can work, and cleaning should remove disinfectant residues (clause 4.33);
• more than one type of disinfectant with different modes of action should be used, and a sporicidal agent should be used periodically (4.33);
• monitoring should show whether the programme works and whether resistant organisms are appearing (4.33);
• the disinfection process should be validated on the surface materials concerned, and the validation should support the in-use expiry period of prepared solutions (4.34);
• disinfectants and detergents used in grade A and B areas should be sterile before use (grade C and D too, where the contamination control strategy requires it); diluted solutions should be prepared so as to prevent contamination, monitored for microbial contamination, stored in previously cleaned (and, where applicable, sterilised) containers and kept only for the defined period (4.35);
• where fumigation or vapour disinfection is used, its effectiveness should be understood and validated (4.36).

USP general chapter <1072> Disinfectants and Antiseptics gives background on selecting and using disinfectants in controlled environments and notes that disinfectant residues themselves are a contamination risk.

Where a plant is non-sterile, the same ideas apply in a risk-based way, but the Annex 1 sterility requirement for grade A/B is specific to sterile manufacture.

Objective

To describe how disinfectant solutions are prepared, labelled, used and discarded at the manufacturing facility.

Scope

Applies to disinfectant solutions prepared and used for surfaces (floors, walls, furniture, drains) and for hand antisepsis in the production area.

Responsibility

• Officer / Executive (Production): prepare the solutions as per this SOP and record them.
• Head of Production (or designee): ensure correct use and training.
• QA / Microbiology: approve the disinfectant list, validation data and rotation plan.

Procedure (example)

Use quantities and concentrations from your own disinfectant validation; the figures below are an example in-house criterion.

1st and 2nd disinfectant solutions (floors, walls, furniture)

1. Take about 9.90 kg of purified water in a clean stainless steel container.
2. Add 100 ml of the disinfectant (1% v/w example).
3. Make up to 10 kg with purified water and mix well.
4. Label the container with name, concentration, date and time of preparation, expiry and preparer’s initials.

Prepare the 1st and 2nd disinfectants in the same way, each with its own container. Add the disinfectant to the water, not the reverse.

Hand antiseptic (3rd solution)

Use as supplied, undiluted (follow the manufacturer’s label). Dispense enough to wet the hands and fingernails and rub until dry. Keep away from flames, heat sources and open electrical wiring, and avoid contact with eyes and ears.

Drain sanitisation

Example in-house criterion: prepare 15 kg of solution for 7 drains in the production area. Adjust to your own drain count and validated dose.

Notes (example in-house criteria)

1. Scale the quantity up or down in the same proportion when a different volume is needed.
2. Prepare solutions fresh. Example: use within 24 hours of preparation and discard any remainder at the end of the day’s work by flushing to drain with plenty of water. The actual in-use expiry must come from your disinfectant validation (Annex 1, clause 4.34).
3. Rotation example: 1st disinfectant for the first 15 days of the month, 2nd disinfectant for the rest. Rotation interval and choice of agents should be justified by your monitoring data, and a sporicidal agent should be included periodically.
4. Do not mix different disinfectants or antiseptics.
5. Do not use a disinfectant after its expiry date.
6. For composition, shelf life and other details of each disinfectant, refer to the disinfectant specification SOP.
7. In grade A and B areas, use sterile disinfectants, and prepare and store dilutions so that they are not contaminated (Annex 1, clause 4.35).
8. Clean surfaces first; disinfection works poorly on visible soil.

Records

Record each preparation (disinfectant, batch number and expiry, volumes, time, preparer, checker) in a logbook or Annexure I format. Retain these records at least 1 year after the expiry date of the respective product batch(es) produced in the area (EU GMP Part I Chapter 4 clause 4.11, or 5 years after QP certification if longer; 21 CFR 211.180(a)), longer if local law or the marketing authorisation requires.

Training and distribution

• Training: Head of Production or designee trains production staff.
• Distribution: as required, under document control.

Annexure

• Annexure I: Record of preparation and usage of disinfectant solutions (1st / 2nd).

Abbreviations

SOP: standard operating procedure; v/w: volume per weight; QA: quality assurance; CCS: contamination control strategy.

Frequently asked questions

Is 1% the correct concentration? No concentration is universally correct. Use the manufacturer’s label and your own validation.

Why rotate disinfectants? Annex 1 expects more than one agent with different modes of action plus periodic sporicidal use, supported by monitoring for resistant flora.

How long can a prepared solution be kept? Only as long as your validation supports (Annex 1, clause 4.34).

See also

• SOP for equipment cleaning in the production department
• Production of sterile pharmaceutical products
• SOP on microbial testing of drain water

References

1. European Commission, EudraLex Volume 4, Annex 1: Manufacture of Sterile Medicinal Products (2022 revision), clauses 4.33 to 4.36.
2. USP-NF, General Chapter <1072> Disinfectants and Antiseptics (USP-NF, 2017 online listing).
3. European Commission, EudraLex Volume 4, Part I Chapter 4 Documentation, clause 4.11.
4. US FDA, 21 CFR 211.180(a), General requirements (records retention).