[becchino]

Dear.. as indicated in paragraph 4.2.2 of the European Pharmacopoeia, it is necessary that the replications relating to the correction factor respect a max rsd of 0.2 it is really difficult to obtain this repeatability. especially for low concentrations.. do you have any ideas?

[marquis]

Yes, it is difficult.  It's best to read all the related paragraphs, because sometimes there's a bit of an out.  But that value is not too strange for either the EP or the USP.  It can make titration quite interesting.  There are some tricks played.  Some of the techs would make sure their weights were always as close to identical as possible ( before dissolving a reference standard, if done by weight). Then the titration volumes should be nearly the same, as well.  And trying to get by with the minimum amount of indicator and using white surfaces, as well as good volume reading, helps a lot.  The automated equipment was only helpful if doing many identical standardizations.  It was usually more of a pain than it was worth to us.  Good luck.