query about HPLC and HPTLC peaks obtained

[vshyam81]

respected forum...

i am a postgraduate student pursuing my masters in pharmaceutical analysis from india, respected forum, in my disertation work, i was asked to develop an stability indicating chormatographic method validation for certain anticancer drugs(tyrosine kinase inhibitors).

as my stability indicating method was validated in HPLC my major degradant was obtained before my drug, to be more clear, my degradant peak at 3.3 and my drug rt at 4.8min.the detector was an u v detector.

i only had one degradation product and as i mentioned the Rt was at 3.3mins. so with this method i did validate my method using acetonitrile and water in the ratio of 70:30.

after this i tried to reproduce the same method in a different chromatographic method,HPTLC... while performing this i did start all my problems, as HPLC WE USE REVERSE PHASE COLUMNS...and in hptlc we use normal silica f254 merck plates....

the exact problem is that i did try many mobile phases from toluene:methanol to ethanol :chloroform for hptlc...... while using in each in mobile phases i did get the same result as that of hplc,that is, the degradation peak was eluted earlier and the drug later.

respected forum... logically i think we should get the opposite result i think as the both r using normal and reverse phase eluting techniques.....

respected sir, will there be any reason to withstand my result in both or should i be changing the method, if so......how should i move..... am in a real confusion as my thesis is on to an end position.......

i hope the experts in this forum will help me out to solve this problem...... or give me a valuable reason to withstand my results if more details required pls i will provide with chromatograms.....

requesting& waiting your valuable replies......

thanking you,

yours sincerely

vivin

[tom jupille]

This is a question which should be discussed with your professor/advisor, however:

1. While elution order is usually opposite in normal vs reversed-phase chromatography, so-called "secondary" interactions with residual silanol groups on reversed-phase packings can make a major contribution to selectivity, so that it is possible to have the same elution order (especially for closely related compounds).

2. If I were your professor, I would suggest that you collect/extract your two spots from the TLC system and inject each onto the LC to confirm that the spots/peaks correspond.

[Kostas Petritis]

Are you sure you only have one degredation product?

How do you detect with HPTLC? Is it possible that you have more degredation products but only one with UV absorbance?