Posted: Wed Oct 14, 2009 11:02 am
trying= varying pH, temperture and organic compostion.............this was mostly performed on the other columns as well
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Separation of 2 peaks elutaing at approimately the same RT
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Posted: Wed Oct 14, 2009 11:07 am
ok, good, do you see in any of your experiments two peaks instead of one, some sign of resolution?
Posted: Wed Oct 14, 2009 11:59 am
How about SymmetryShield?
Posted: Wed Oct 14, 2009 11:59 am
yes........but the problem is the pencilloic acid has 2 peaks, one broad small peak at approx 8mins and the other at 12mins( narrow peak..good peak shape)......so they kinda stretch out over a 5 minute retention. the sodium benzoate is in and around this retention time...so if you separate it from one peak it usually runs into the other!!
Posted: Wed Oct 14, 2009 12:12 pm
we have no SymmetryShield in house...thanks Uwe for sending those papers on solvent and stationary phase selection
Posted: Wed Oct 14, 2009 12:12 pm
that's kinda interesting 
is this the acid?
http://en.wikipedia.org/wiki/Penicillic_acid
is it included in pharmacopoeia as impurity? does the Ph states that there shoul be two peaks?
Anyone knows if existence of two forms is pH dependent?
is this the acid?
http://en.wikipedia.org/wiki/Penicillic_acid
is it included in pharmacopoeia as impurity? does the Ph states that there shoul be two peaks?
Anyone knows if existence of two forms is pH dependent?
Posted: Wed Oct 14, 2009 12:31 pm
no...its Penicilloic acid of phenoxymethylpenicillin...and yes is an EP impurity. the reason it has 2 peaks ..i think due to its isomer number 1,2 and 3 penicilloic acid.
Posted: Wed Oct 14, 2009 12:44 pm
could you post structures of these isomers?
Posted: Wed Oct 14, 2009 1:00 pm
What is the injection solvent ?
Peter
Peter
Posted: Wed Oct 14, 2009 1:02 pm
Phenoxymethylpenicillin Potassium Imp. E (EP): (4S)-2-[Carboxy[(phenoxyacetyl)amino]methyl]-5,5-dimethylthiazolidine-4-carboxylic Acid (Penicilloic Acids of Phenoxymethylpenicillin)
Hope this helps
Hope this helps
Posted: Wed Oct 14, 2009 1:11 pm
I meant the pictures or link to the pictures 
Posted: Wed Oct 14, 2009 1:12 pm
injection solvent/Diluent= 6.81g KH2PO4 in 1000ml DH20 with adjusted pH with 0.2m NaOH to pH6.5
Posted: Wed Oct 14, 2009 1:49 pm
Now, why would the pH of the sample solvent be 6.5 whilst the mobile phase’ pH is intended to be 3.5?
I write “intendedâ€
I write “intendedâ€
Posted: Wed Oct 14, 2009 2:11 pm
Sorry...i spent the last 30mins trying to transfer the structure to the post..i couldnt do it. I can give you link
http://www.lgcstandards.com/media/559600807.pdf
you will have to download the catalogue...go to page 312 to see its structure.
About the difference of pHs of moblie phase and diluent...well thats the way they have it in the EP!...i thought it was a bit strange as well!
http://www.lgcstandards.com/media/559600807.pdf
you will have to download the catalogue...go to page 312 to see its structure.
About the difference of pHs of moblie phase and diluent...well thats the way they have it in the EP!...i thought it was a bit strange as well!
Posted: Wed Oct 14, 2009 2:13 pm
injection volume 20uL