Cleaning Validation – Rinsate and Swab Sample; Test Method Development and Validation
Introduction
The guidance describes recommended approaches to develop and validate sampling and test methods for cleaning verification using rinse and swab samples.
Recommendation & Rationale
Training Colleagues that perform sampling and testing activities (e.g. development or routine testing activities) in support of validation need to be qualified to perform those tasks.
Laboratory Analysis
A description of the laboratory method selected and the rationale for its selection should be included in the method validation report. Analytical techniques such as HPLC, UV, TLC (thin layer chromatography), TOC (total organic carbon) and GC are commonly used at GMP sites for this analysis.
Protocol Contents
Contents of Equipment Cleaning Analytical Method Validation Protocols should include or reference the following:
- Approval signatures and dates of approvals
- Sampling Method
- Analytical Method
- Experiments to be executed; and
- Acceptance criteria including the Residue Acceptance Limit (RAL)
Method Validation
Method validation should encompass the residual limits for each product and/or equipment item.
Method validation shall be performed in accordance with guidelines “Analytical methods for Equipment Cleaning”.
Method Specificity
The cleaning evaluation for a given product, intermediate or drug product excipient provides the basis for the rationale of which material(s) should be tested for during the analysis. The analytical method selected shall be able to detect residual product at the acceptance level specified. Specific test methods are not required. Specificity experiments should be based on the type and purpose of the method being considered.
If a specific method is being validated, then specificity studies need to be performed for the analyte of interest. The potential for interference from the following should be considered:
- Swab extractables
- Cleaning agents
- Sample containers and lids
- Excipients and other compounds potential present
If a specific method is being validated for a cleaning agent, the only specificity experiment typically executed is specificity from swab extractables.
Range
The equipment cleaning analytical method should be validated around the calculated RAL for the material. The method is considered valid for any RAL within the validated recovery range. If the RAL falls outside the validated recovery range, the method should be revalidated with respect to the affected elements (e.g. range, linearity).
Linearity
Linearity should at a minimum cover the expected analyte RAL and encompass the levels included in repeatability and recovery studies. The lower end of the linearity study shall take into consideration the correction factor for sampling recovery, if applicable (e.g. if the RALs have a range of 4-6 ug/cm2 and the recovery is 50 percent, the linearity study should include levels of 2-6 ug/cm2 ).
Intermediate Precision
Intermediate precision is the study of the effects of random events (e.g. days, analysts, equipment etc.) on the precision of the analytical procedure. A method intermediate precision experiment should be conducted unless there is a documented rationale otherwise (e.g. a reliable and robust swabbing verification program is implemented). Method intermediate precision should include use of a second Lab Analyst, on a different day, using different solutions and different analytical equipment, if possible.
System Suitability
System suitability should be conducted for systems such as HPLC and TOC. Although non-specific methods like UV, pH etc. may be used; the ability of the selected method to detect the residue shall be demonstrated (for example UV absorbance at the residue maximum wavelength and non-interference of the rinse solution).
Recovery Studies
Analyte residue recovery shall be challenged as part of the analytical method validation. The recoveries of each material (product or cleaning agent) from the different process-contact surfaces that constitute the major portions of equipment’s surface area are typically demonstrated. Alternatively, the recovery value of a worst case material could be substituted for all the materials sampled with the same rinse solvent.
Typical surfaces may include hastelloy, stainless steel, glass/glass lined carbon steel and PTFE (polytetrafluoroethylene).
The solvent used in the recovery study should be the same as is used for routine sampling.
Recovery studies should include replicate or repeatability studies to confirm reproducibility of results.
An acceptance limit should be specified for the allowable variation in results of these replicate studies (e.g., 15%) to ensure recovery is equivalent within the range.
The minimum rinse time and rinse volume should be fixed based on the recovery studies.
Site procedures may combine recovery from the surface and recovery from the swab in a single recovery study.
Site procedures should specify a minimum percentage recovery from the surface. If recovery values are less than 70%, the recovery value must be used as a correction factor in the calculation of results or limits. For recoveries greater than 100%, no recovery values are to be used as correction factors.
Stability
The stability of the product or cleaning agent standard and sample, as well as the stability of the residue on the swab (if applicable) should be established. This study provides a valid hold time for the samples prior to testing to ensure accurate results.
Qualification and Training of Swabbing Personnel
Personnel should be qualified to swab samples through comparison of the trainee’s recovery results from a coupon containing a predetermined amount of material at one concentration (approximately 100% of RAL) using the substrate from which it is most difficult to recover the analyte. The results of the trainee’s recovery should meet the acceptance criteria described in the site SOP (for example, within 15% of the known amount) to qualify them.
Solvent Selection for Rinsate
Solvent selection for rinsate should be based mainly on product solubility in the rinsate solvent. However, a solvent that reduces the sample prep for the analytical method (e.g. one that is compatible or the same as the sample diluent) may be desirable. Solvent handling practices, safety and environmental requirements should be considered when selecting the rinsate solvent.
Swab Selection
The type(s) of swab to be used must be defined for consistency. The type of swabs used to collect samples from the equipment in the plant should be the same as those used in the recovery studies.
If a special swab is required for a particular product it should be documented. The rationale to use the same swab for all products and/or specific types should also be defined.
There are several swab types and sizes to choose from in the marketplace, and while there is no standard swab type that is required, the following short list of swabs has been recommended for use by site subject matter experts:
- Texwipe Alpha Swabs TX761
- Texwipe, Large Alpha Swab. #TWTX714A
- Alphawipes
- Non Woven Swabs NT2300
Swab Pre-treatment
If it is determined that special pre-treatment is required for the swabs, the Standard Test Procedure should define what is required. It should include the type of pre-treatment to be performed prior to use of the swabs, storage conditions and/or shelf life of treated or untreated swabs. Special requirements related to the swab or product may also be included.
Area Swabbed
The area to be swabbed must be defined, typical areas range from 5cm x 5cm to 4” x 4”. It shall include special requirements and/or calculations for specific areas or equipment. It should be constant and well defined at each site to ensure consistency.
This may be a standard area, as defined by site procedure (and executed using a template), or may be a specific area for that piece of equipment. The actual area to be swabbed may be defined in the validation protocol.
Swabbing the defined area called for by the test procedure can sometimes be difficult on the shop floor. For example a mill screen or sieve might have been identified for swabbing; however, the irregular surface might make it difficult to accurately swab an accurate surface area. The following is guidance on this problem:
- Choose solid, flat or semi-flat surfaces when selecting swab locations, if possible. Swab locations should be chosen based upon their difficulty to clean not the difficulty to swab sample.
- If a porous or irregular surface must be swabbed some consideration should be given regarding how much the swab surface area should be adjusted to correct for the change in availability of surface area when sampling a mesh or irregular surface. The typical swabbing instruction of “swab a “25cm X 25cm” area can be modified to fit the specific case. In any event, if the surface area to be swabbed is changed in the geometric plane of primary interest to accommodate an irregular shape, the rationale should be documented.
- A template of a non-porous material can be fabricated and used as a guide to ensure the individual performing the swab sample swabs the specified area. A flexible material would be preferred to allow for the template swabbing of curved surfaces.
- Individuals who perform swab sampling can demonstrate their proficiency at swabbing an accurate area without templates by comparison of their “free hand” recovered values to a recovery value obtained using a measured area.
Swab Standard Test Procedure Content
The intent of this section is to provide guidance on the development and content of Standard Test Procedures (STP) with the possibility of transfer of the STP to another gmp site with limited or no revalidation resource required by the receiving site. To facilitate the transfer of swab methods between sites and to achieve a greater uniformity of test methods at all gmp sites STPs or SOPs should include:
- Swab type
- Number of swabs per zone, and whether wet (stating solution moistened with) or dry.
- Swab technique
- Swab area
- Surface types that the recovery is applicable to
- Extraction technique
- The Limit Of Quantitation (LOQ) of the method
The range (in µ g/swab) over which the method is validated; Different criteria may be applied to generate this according to site procedures.
Examples of this could be:
1. a) proving linearity of results from swabbing spiked coupons at a range of concentrations and compared to linearity of the test method, or
1. b) by performing the recovery at 50%, 100% and 150% of the RAL, and thus proving the recovery is applicable to this range of concentrations.
If a recovery is performed at 50%, 100% and 150% of the RAL and all three recovery values are within the criteria set at the originating site; the originating site should report the mean of the three values expressed as a percentage. As the individual recovery values are within set criteria, this mean should be “similar” to all 3 values obtained.
If the values for the recoveries performed individually at 50%, 100% and 150% are within acceptance criteria but are significantly different from the mean, then the method would probably not be transferable and the STP should document this fact. Because the range over which the recovery applies could not be reported with certainty; the changing recovery values with concentration could not be assumed to be the same at the receiving site, even if equivalence was shown at one concentration. In this case, another method may need to be developed and validated at the receiving site.
Equivalence of Methods Transferred Between Sites
Adherence to the principles described above by the developing site will allow another site interested in receiving a test method to focus on what is required in order to establish equivalence (i.e. to confirm the method is suitable for use at the receiving site).
The following should be considered when transferring a method to another site with different swabbing practices; equivalence should be demonstrated as follows:
- Ensure the validated range is adequate for the receiving site. If the validated range needs to be extended, then a separate swab linearity study should be performed by the receiving site over the required range.
- Perform a recovery on 6 coupons using the receiving site’s procedure. This should be performed at the lowest RAL for that product at the receiving site.
- Calculate the mean of the 6 recovery results. If the absolute % difference between the mean recovery and that stated in the originating site’s STP is not greater than 15%, then the recovery value stated in the STP will remain unchanged (e.g., if the STP states a recovery of 85%, then the receiving site would target to obtain a recovery of 70% to 100%).
- Calculate the RSD of the 6 recovery results. If the RSD is not greater than 15%, then the new technique is considered acceptable (providing the mean result meets the criteria above).
- An STP, stating the new conditions/technique/extraction should be written, referencing the equivalence proven to the originating STP
- If the mean and RSD criteria are not met, then equivalence in not proven, and the following could be performed:
Use an alternative sampling technique, and try to prove equivalence.
Perform a full validation using the new technique.