
 Posts: 8
 Joined: Mon Aug 11, 2014 7:13 am
I'm trying to repeat the latest version of European Pharmacopoeia analytical method (:1317), Ethanol (96%) / Volatile impurities (GC).
Link to previous version:
http://www.drugfuture.com/Pharmacopoeia ... /1317E.PDF
In newest method version only acetaldehyde + acetal calculation formula was changed:
[(10 x Ae)/(At  Ae)] + [(30 x Ce)/(Ct  Ce)] x (44.05/118.2)
For analysis I'm using DB624 30m x 0.32 mm x 1.8 µm
As result I'm getting following areas of the peaks:
 4methylpentan2ol (Test s. B)  157
 Methanol (Ref. s. A)  35
 Acetaldehyde (Ref. s. B)  2.6
 Methanol (Ref. s. B)  1.8
 Acetal (Ref. s. C)  9.1
 Benzene (Ref. s. D)  1.2
In method is written that I supposed to used disregard limit that is "0.03 times the area of the peak corresponding to 4methylpentan2ol (Test s. B)". So if I understood correctly disregard limit supposed to be 4.7.
So the first question is, do I need to apply calculated disregard limit to both Test solutions (A and B), or it's only for Test s. B?
The second question related to Acetaldehyde + Acetal calculation formula. In case in Test s. A Acetaldehyde or Acetal peak area is bigger then correcponding peak area it Ref. s., then calculation result will be negative.
How such cases supposed to be handle?
I checked all topics on the forum that related to this method, but unfortunately I can't find answers.
Thank you in advance,
Dmitrij