As part of sampling suitability testing, process residues of the new product are evaluated for recoverability by rinse and
swab sampling methods. In this study (also known as recovering organic carbon by rinse and swab) total organic carbon (TOC)
is analyzed to determine the sampling method that is appropriate for cleaning validation testing.
Soils from fermentation, initial purification, and final formulated bulk are used in this study. Testing is performed on each
surface type (e.g., stainless steel and glass). Before spiking, soils are adequately mixed before use (by gentle inverting
of the sample tube for fermentation soils or by vortexing for recovery soils). Coupons are prepared (cleaned and dried) and
are spiked with protein soils at TOC concentrations similar to those in the cleaning validation acceptance criteria limit.
The soiled coupons are dried for at least 24 hours, or for the specified dirty hold time, and are sampled using the rinse
or the swab method. Positive and negative controls are generated, and swab and rinse water recoveries are calculated.
For highly soluble proteins, the average results of rinse and swab sampling recovery studies for fermentation, initial purification,
and final bulk soils usually vary between 80% and 120%. If average recovery results for rinse or swab sampling methods is
outside the acceptable range, an investigation is undertaken and a correction factor is applied for less-than-minimum recovery
when reporting the equipment validation TOC results. WHO has set the following recovery levels: greater than 80% is good;
greater than 50% is reasonable; and less than 50% is questionable.7 However, the key to recovery is consistency between samples, not just total recovery.
The overall study challenges the ability of the standard cleaning procedure to remove the new product soil from representative
The cleaning process is challenged by including the maximum dirty equipment hold time.
The cleaning process may also be challenged by reducing one or more cleaning process variables—such as cleaning time, flow
rate, or volume—during each run.
Sampling for residues includes rinse sampling, swab sampling, and visual inspection. An evaluation is performed to determine
suitability of swab and rinse methods for validation sampling.
The product residue acceptance criteria in a cleanability study are calculated using the same principles and calculations
as for a validation protocol for equipment used to make marketed products. Acceptable results in the cleanability study allow
a new product to be introduced and validated in equipment for marketed products; acceptable results also increase confidence
in successful validation runs. Cleaning validation of the major multi-use product-contacting equipment is executed concurrent
with manufacturing. Acceptable results in triplicate runs of a cleanability study in one facility constitute an acceptable
basis for introducing the product into the same combination of equipment configurations and product-contact surface types
in any other facility, after equivalence of equipment, cleaning methods, sampling, and acceptance criteria has been established.
This equivalency should be documented in the validation protocol or in a technical report. Currently, data from full-scale
cleaning validation and new product introduction methods are being generated at Genentech to determine worst-case situations
and to justify reduced testing.
Cleaning validation is driven by regulatory requirements to ensure that residues from one product will not carry over and
cross contaminate the next product. Appropriate design of cleaning equipment and cycle development increases success rate
and reduces validation execution time. At Genentech, the cleaning program consists of equipment design and qualification,
cleanability study, sampling evaluation, and meeting predetermined validation protocol acceptance criteria. Dirty and clean
hold times are established during cleaning validation. Cleaning validation is supported by approved procedures and by training
programs for personnel who perform the cleaning operations in the production areas and who collect validation samples. Part
2 will discuss implementation of the cleaning validation program—grouping strategy, various types of sampling and their acceptance
criteria, training, change control, and revalidation.
The author is thankful to corporate quality management at Genentech, Inc., for support, and to Jenna Carlson and Ahmed Bassyouni
for reviewing the manuscript and providing comments.
A. Hamid Mollah, PhD, is a senior technical manager for corporate quality and validation at Genentech, Inc., South San Francisco, CA, 650.467.1095,