Chromatography Forum

I have a L35 column and a RID detector, but the areas of the peak of zoledronic acid are so small.
Somebody have experience in these product...?
Thanks

Because you have provided so very little information (what else is new on this board). I can only give some guesses.

Peak are too small. what can you do?

1: Are they really to small? You seem to be able to detect them, if you can detect them at a signal to noise of greater than 10, then they really are not too small.
2: Inject More
3: Use a narrower bore column (makes taller peaks)
4: Use a more concentrated sample
5: Use a better RID (you don not say which you use, so this may this may not help at all.
6: Use a different detection device, ELSD pops to mind, or maybe you can derivitize your compound and see it by UV of FLD at a higher response factor.

Here is example of ELSD detection for various *dronic acids.
http://www.sielc.com/compound_248.html

Zoledronic acid is UV active at 200-220 nm due to the presence of imidazole fragment:
http://webbook.nist.gov/cgi/cbook.cgi?I ... V-Vis-Spec

I have a L35 column and a RID detector, but the areas of the peak of zoledronic acid are so small.
Somebody have experience in these product...?
Thanks

Elsewhere you say you have an L23, which I think is an anion-exchange quat ammonium column. The sensisitivity will depend on the stability of your detector, mobile phase, baseline, and the amount injected. For RI, temperature stability is critical to obtain stable baselines. Some of these bisphosphonate compounds can be difficult to quantitatively elute off ion-exchange columns using isocratic systems.

If the method worked before, what has changed?. If the method is new, what sensitivity do you want, and how close to that are you?.
If you are well away from the desired sensitivity, and the Ri is working to spec, then I would recommend using another method.

There are UV and ELSD reverse phase methods using tetrabutylammonium ion-pairing, listed on Pubmed. ust search on HPLC and Zoledronic Acid.

eg
"Separation of zoledronic acid and its related substances by ion-pair reversed-phase high performance liquid chromatography"
Zhang X, Jiang Y, Xu Z.

"A rapid and simple ion-pair reversed-phase high performance liquid chromatographic method (HPLC) has been established for the routine analysis of zoledronic acid and its related substances. ... The excellent separation of zoledronic acid from its related substances, including the remaining imidazol-1-ylacetic acid used in the synthesis of zoledronic acid and other impurities of oxidation and decomposition, was achieved within 9 min on a Hypersil C8 column with UV detection at 220 nm. The mobile phase was a mixture of methanol (20%) and 5 mmo/L phosphate buffer (80%) that contains 6 mmol/L tetrabutylammonium bromide. The resolution factor of zoledronic acid from its adjacent peak was more than 2.5. This is a simple and rapid method for the routine assay of zoledronic acid. "

Bruce Hamilton