The measurement methods used here and their respective recovery rates are summarized in Table V. When using the rinse- and swab-sampling methods, some of the water-insoluble substances had high recovery rates while others
had low recovery rates. It is thought that this may be due to differences in the affinity with which the substances adhere
to the stainless steel pot. Accordingly, it is possible that residue evaluation using these methods would be difficult for
substances with low recovery rates.
Table V: Summary of measurement results.
In contrast, high recovery rates were obtained for all the substances when using the swab sampling with direct-combustion
method, regardless of whether the substances were water soluble or water insoluble. Therefore, this method is considered to
be the most versatile measurement method for conducting cleaning validation, especially when multiple compounds are being
manufactured in the same vat, if the compounds are unknown, or if there is a possibility the known compounds will decompose
into other compounds.
Robert Clifford*, PhD, is industrial business unit manager at Shimadzu Scientific Instruments, 7102 Riverwood Drive, Columbia, MD 21046, tel. 800.447.1227,
. Minako Tanaka is a scientist at Shimadzu Applications Development Center, Kyoto, Japan, firstname.lastname@example.org
*To whom all correspondence should be addressed.
Submitted: Nov. 17, 2011. Accepted: March 12, 2012.
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