"Limit test" vs. "Titration" in a pharmaceutical guide From the "Technical guide for the elaboration of monographs" by EDQM, edition 7, 2015, page 35:


  Where the introduction of tests for foreign anions in organic substances is considered then a single one, either for chlorides, sulfates or − less commonly − nitrates, will usually suffice even when several could theoretically be present. The test is then to be carried out on the most abundant anion. When a test for chlorides is considered, up to 1000 ppm (0.10 %), a limit test should be used rather than titration.


I don't understand this. Isn't titration one of the possible ways to perform a limit test (to check whether the chloride content is within the specified limits)? 

Maybe my understanding of "limit test" is flawed?
From what I know, rules for making a monograph are not about giving an exhaustive list of all the analyses possible. Guides describe international agreements about what is recommended and sufficient to identify a substance and its impurities.

A titration is considerably more tedious to perform and validate (see ICH Guideline). If you use titration in a monograph, people referring to it will also have to use this method. Unless you also included a limit test but, if you did so, why bothering carrying out titration? Overall, you would waste your time and, most importantly, others' time.

So the sentence "limit test should be used..." should be read "we agreed that a limit test gives enough information in this context and we prefer it over titration".

HTH