Chromatography Forum

Hello all-

LC/MS question. I have a validated stability indicating HPLC Purity Method which is comprised of the following mobile phases ratios containing 20mM H2SO4/ACN, A=95/5 and B 75/25. with a 250 SB Phenyl (4.6). Iso for 25 mins then to 100% B in 30 mins.

I am looking to access peak purity of the main band however (rt 23 mins), the use of sulfuric acid on our HPLC-MS is trying to be avoided. So, i am looking for a substitute to the sulfuric acid in the method when so i can run via. MS and keep the methods as similar as possible. Making major changes to the MS method is not desirable because i need to make a direct correlation to the HPLC data previously generated with the validated method. If i change the method too much, then i have no direct comparison back to the data. The main band is resolved between two neutral peaks at ~1.9 for both.

So to boil it all down i am looking for an MS compatible modifier equivalent to H2SO4.....

The best one I can think of is probably TFA. Second choice would be formic acid. Use about 0.1% by volume of either. If you must use negative ionization though, then don't use the TFA, use formic acid instead.

Definitely I would concur that H2SO4 should not be used with LC/MS. Once in grad school I accidentally infused some dilute sulfuric (less than 100mM) into a hot ESI source for a few minutes before I realized the mistake. It attacked and pitted some of the stainless steel parts.

Thanks for the reply, i am already heading in the TFA route at 0.2%. I will tinker with the % as needed.

Formic doesnt work