Chromatography Forum

Hi.
I have a doubt in one of my LCMS method development The molecule is a fluroquinone. I am using a mobile phase of ACN: 0.1% Formic acid (pH adjusted to 3.0) 80:20. The column is a C18 column. I am able to elute the compound comfortably, but the peak is tailing. So I want to add an organic modifier (triethyl amine)to supress the tailing. I want to know the optimal concentration and composition of TEA to be used in the mobile phase. One more problem is that the base noise in also high.
Please give me a solution to counter these problems.

My email id is: jbshan@gmail.com

Shan

I think the rule of thumb for Electrospray LC-MS is to keep buffers around 10 mM to avoid ion suppression, so maybe you should start there.

Thanx for your suggestion. Hope it works.

Shan

You'd better not use TEA mobile phase in MS.

I thought maybe 0.01% TFA will work for the peak tailling.

I would also be inclined to try TFA if Formic is not cutting it.
TEA is not so good for MSDs.

Dear friends,
Thanx for your suggestions. But still I have indications in some of the articles that TFA should be avoided when using electrospray LCMS because it reduces sensitivity. That's why I was inclined towards TEA. Anyway I will try using TFA as one of my options.

Shan

I have hard time finding structure for fluroquinone. Google gives suggestions of "fluoroquinolone structure"
Are you talking about this class of compounds:

http://en.wikipedia.org/wiki/Ciprofloxacin

if not can you post the structure?

Thanks,

Vlad

Shan,

I analyse fluoroquinolone using 0.1% Formic acid in H2O for aqueous mobile phase and 0.1% Formic acid in ACN for organic one. The column used is Luna C18(2) column. I don't observe any problem in peak tailing. I suggest you'd better check your C18 column should it be already soiled; or try using a better endcapped C18 column.

Shan,

I analyse fluoroquinolone using 0.1% Formic acid in H2O for aqueous mobile phase and 0.1% Formic acid in ACN for organic one. The column used is Luna C18(2) column. I don't observe any problem in peak tailing. I suggest you'd better check your C18 column should it be already soiled; or try using a better endcapped C18 column.

I'd avoid the TFA if this is going into an MS-too much ion suppression. Have you tried using something other than a silica-based C18 column? We see nice fluoroquinolone peaks on either a YMC Phenyl column or a PLRP-S (Polymer Labs) column.

In my opinion it is better not to use TEA buffer for ESI MS as Tri ethyl amine suppress the Ion formation,instead u can check with the column to reduce the peak tailing.

I think at t 0.01% TFA, there shouldnt be much ion suppresion so if you want you can try. We always use 0.01% TFA but for peptide analysis. Do not use >0.01% TFA.

Ananda