It is necessary to use recovery factor for accurate results in cleaning validation of pharmaceutical manufacturing equipments. Recovery factor is the recovery of swabbed material from the equipment to the solution.
When we take sample from the equipment with the cotton swab the entire API associated with the equipment is not removed by the swab and this error of recovery is managed by the recovery factor during the calculations in cleaning validation.
Solution of know concentration of API is applied on the stainless steel plate of 10 cm2 and allow the plate to air dry. Swab the plate by the cotton swab and dissolve in appropriate diluents. Diluents should be prepared on the basis of the solubility of the active ingredient. Sonicate the cotton swab and diluents for 5 minutes to dissolve the content properly. Makeup the solution with the diluents to get the desired concentration as standard solution is prepared.
Mix the solution properly and analyze as per the method of analysis using HPLC, Ultra Violet spectrophotometer or titration. Calculate recovery factor by the following recovery factor formula:
% Recovery = Area of swab sample solution x Standard dilution x 100
Area of the standard solution used x Sample dilution
Recovery Factor = 100/ % Recovery
Suppose % recovery of any swab is 80% then recovery factor of that swab shall be 100/80=1.25. Results are multiplied by 1.25 to increase the results by 1.25 times that was lost during the swabbing. Recovery calculation should be done for both chemical and microbiological sampling in same manner.
FDA has suggested determining the % recovery of contaminants from the equipment surface in cleaning validation guidelines but the limit of recovery is not written clearly.
WHO guidelines also say that there should be evidence of the proper recovery of the samples. According to WHO TRS 937 (page 133) a recovery of >80% is considered good.
Also see: Cleaning Validation Protocol
Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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