Hi
Not really, ICH Q2 generaly states:
for the determination of an impurity: from the reporting level of an impurity to 120% of the specification; with a reference to ICH Q3A and B for normal impurities (not PGIs etc) and their expected minimum LOQ/reporting limit.
ICH Q3C do not add to this, however Eu (EMA) has defined what is required to call a residual solvent (mainly class 2 solvents) "not likely to be present" and conseqently be left out of specification. This may have impact on your validation strategy, if you have class 2 solvents earlier in the process and want to omit them from specification you need to go for 10% of the respective ICH Q3C limit i.e 89µg/g for toluene.
If not of interest, 50% of ICH Q3C specification is usually good enough.
Link to EMA annex to ICH Q3C with data requirements:
http://www.ema.europa.eu/docs/en_GB/doc ... 002979.pdf
I like this guidelines because you build your case on the manufacturing process (what goes in where), science (where is redues removed/evaporated) and actual data (confirming the theoretical stuff).