Separation of 2 peaks elutaing at approimately the same RT

[seamoro]

trying= varying pH, temperture and organic compostion.............this was mostly performed on the other columns as well

[grzesiek]

ok, good, do you see in any of your experiments two peaks instead of one, some sign of resolution?

[Uwe Neue]

How about SymmetryShield?

[seamoro]

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!!

[seamoro]

we have no SymmetryShield in house...thanks Uwe for sending those papers on solvent and stationary phase selection

[grzesiek]

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?

[seamoro]

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.

[grzesiek]

could you post structures of these isomers?

[Peter Apps]

What is the injection solvent ?

Peter

[seamoro]

Phenoxymethylpenicillin Potassium Imp. E (EP): (4S)-2-[Carboxy[(phenoxyacetyl)amino]methyl]-5,5-dimethylthiazolidine-4-carboxylic Acid (Penicilloic Acids of Phenoxymethylpenicillin)

Hope this helps

[grzesiek]

I meant the pictures or link to the pictures

[seamoro]

injection solvent/Diluent= 6.81g KH2PO4 in 1000ml DH20 with adjusted pH with 0.2m NaOH to pH6.5

[danko]

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€

[seamoro]

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!

[seamoro]

injection volume 20uL