Help with hydrocodone bitartrate tailing issue

[pko142]

Hi all - I'm trying to improve on a method that i previously developed for the analysis of hydrocodone bitartrate via HPLC.

The problem is that the hydrocodone peak has a tailing factor of ~ 0.85 due to a long slow baseline drift occuring right before the bulk of the drug elutes.

I've tried two different systems thus far with no positive results
1. RP18 column with with KH2PO4 (pH 6 & 4) and NH4H2PO4 (pH 3) buffer
2. C18 column with KH2PO4 (pH 6 & 4) and NH4H2PO4 (pH 3) buffer

the pH of the solution is ~3 and the column is not being overloaded (ie: the baseline drift can be detected at very low concentrations) I have a hunch that the column is still to retentative or i'm just totally overlooking something very important.

any insight would be greatly appreciated.

[DR]

HB tails (our limit is 1.5 at 5% peak height).
We run a ~40 min. phosphate/MeOH gradient (pH3) on a C-8 column at fairly high temperature. HB elutes at abou 13 min.

[SIELC_Tech]

Your tailing is due to residual silanol interaction. There are bunch of columns on the market with extensive end-capping, you can also try to lower pH to suppress silanol activity. We are using a different approach. Check the following link for similar compound (dextromethorphan) with the symmetry of 1.0-1.05. The ligand in Primesep B2 column masks any residual silanol:

http://www.sielc.com/application_066.html

What is good about this approach is that you can retain your anionic counter ion too.

Here is another one for basic compound:

http://www.sielc.com/application_065.html

[MG]

0.85 means fronting, not tailing, right? What's your injection volume, injection solvent, and column i.d.?