By Anonymous on Thursday, June 24, 2004 - 08:27 pm:
Hello, everybody!
I need to analyze low level Cetylpyridinium chloride (0.1%) in a syrup kind sample by HPLC.
The sample also contains Tannic acid (7%), Benzocaine (20%), Benzyl alcohol (4%), Alcohol (24%) and some flavor, dye, oil etc.
The mobile phase is Acetonitrile: water (900:100) plus 5 mL ion pair reagent IPC B6. Phenomenex Primesphere 10u 4.6mm x 250mm column. Wavelength 259nm. Diluent: Acetonitrile.
This condition does not work. Firstly, CPC elutes too early at RT.2.3 min.. Secondly, there is a huge peak very close to CPC peak, and resolution is poor. Thirdly, there is a small peak underneath of CPC peak.
I do not like to use IPC B6. It needs long long time to equilibrium column before run and rinse column after run.
pKa value:
Benzocaine: 8.5
Tannic acid: N/A (pH 3.5)
CPC: N/A (pH 5-5.4)
Can anybody tell me what the problem of my HPLC condition is? Can you give me any suggestion? Thank you in advance!
By Constantin Sychov on Friday, June 25, 2004 - 04:39 am:
No wonder - it is very-very old method, and really ancient phase.
By MG on Monday, June 28, 2004 - 11:36 am:
I don't see a flow rate, but if you are running at 1 mL/min, your peak is unretained on that column, or nearly so. What happens if you reduce the acetonitrile content? You should get improved retention and resolution.
By Anonymous on Wednesday, June 30, 2004 - 08:16 pm:
MG, thanks for your great input. I was running at 1 mL/min. You are right, reducing flow rate and Acetonitrile content maybe the first things to try.