By lee kelly on Thursday, September 19, 2002 - 09:59 am:
hi can anyone explaind to me why 1-heptanesulfonate is used in the mobile phase of the USP assay for aspirin. I understand it is an ion pairing reagent but dont unserstand why it is included in this method. the only peaks expected would be salycylic acid and aspirin.
column C18
molbile phase 2g 1-heptanesufonate 850ml water, 150ml acetonitrile
thanks
By Anonymous on Thursday, September 19, 2002 - 01:10 pm:
It is a USP method. THey do not have to make sense.
By Benjamin on Friday, September 20, 2002 - 04:53 am:
Dear Anonymus;
Your answer is the best one I have heard in years. I feel scared that such seemingly poor methods and conditions are used for control of pharmaceuticals.
Benjamin
By Anonymous on Saturday, September 21, 2002 - 06:41 am:
this is absolutely correct , both can even sperate even with methanol water and phosphoric acid mobile phase with ph 2 to 3
such a stupid things they consider in that method
By Anonymous on Wednesday, September 25, 2002 - 01:24 pm:
Indeed, I always thought USP en EP methods are very robust methods, and I expected that was the reason why they are so complicated. But when you try some methods you get poor peak shape, unseperated peaks, ....
Even manufacturers of HPLC columns don't know what colum is the best for some separations.
Pharmacopea? Only money does make sense!!
By Anonymous on Thursday, September 26, 2002 - 04:43 am:
Once I have used octanesulfonate in MP and diluant to analyse impurity profiles of a neutral drug. The purpose was to have higher solubility.
By Anonymous on Wednesday, October 9, 2002 - 02:48 pm:
Complicated methods are not likely to be reproducible.
If a column manufacturer "does not know which column to use", it means that he does not have the right column in his product line. The best thing to do then is to call another manufacturer.
By A. Buske on Thursday, October 10, 2002 - 02:29 am:
To anon 2002-10-09: They might not have the "right column in his product line". They might also have different columns that can do the separation. They might not have tried your problem on any of their columns. While most manufacturers have applications for tricyclic antidepressants, cough syrup, aspirin etc. , they usually do not have applications to separate one specific drug substance from its degradation products or from specific excipients.
By Anonymous on Thursday, October 10, 2002 - 02:44 pm:
A knowledgeable column supplier should know, which columns have been used to create the method published in the USP. This is not a question of running applications, but simply a question of knowing which columns have been used to run the application in the first place.