recovery factor

hi guys…

i’m a newbie…
i want to know the formula for % recovery
%recovery = conc collect after swab / conc initial

but actually how we can calculate the concentration collect after swab?

other is… we will dip the cotton in the solution after collect the sample, does the concentration change? because we dip as like we dilute it, is it?

sorry, if the question is like dummy…but really i need help…


Dear safni,

the % recovery is not calculated as concentrations. The procedure is simply to spike a known amount of the analyte on a piece of the same material to be sampled (“coupon”), swab it, throw the swab in a known amount of an appropriate solvent, determine the concentration of the analyte in that solution (by HPLC, TOC or whichever analytical method) and, knowing the amount of solvent used, calculate the absolute quantity of the analyte in the solution and hence in the swab. The % recovery is the :

% recovery = 100 * (quantity of analyte in the swab/quantity of analyte spiked on the coupon).

The concentration of the analyte in the solvent after dipping the swab in it (actually, the swab is not dipped because it remains in the solvent) does not change because the amount of solvent is known and does not change.

Best regards


An important consideration is the volume of solvent soaked onto swab tips. The solvent contained on tip might increase the actual volume of extraction solution to more than your target volume, So…in a step of Swabing Method Development you are follow this Step

  1. weight data of solvent soaked on the tip
  2. Convert Weight Data to Volume of soaked solvent by weight per ml
  3. Used Actual Volume(Dilute volume + Soaked volume) for Calculate

See more information at " Method development of swab sampling for cleaning validation of a residual Active Pharmaceutical Ingredient" ,Pei Yang

tq guys…

i try to consider it…maybe with some trial n error.
i’ll come back later, if i stucksomewhere

again…tq a lot:)