Chromatography Forum

Dear all HPLC guru,

I am currently encountering an issue of baseline raise when I use THF in mobile phase B. The details as below:

1. Zorbax Bonus RP , 150mm column
2. Mobile phase A is 0.1%TFA, Mobile phase B is THF:ACN at 1:1
3. UV 278nm
4. Gradient is initially MPA is 86% : MPB 14%. After 15 minute, MPB increased.

I realized that when the MPB starts increase from 15 minutes, the HPLC chromatogram baseline suddenly start raise. The THF i use is without stabilizer for HPLC grade, and I am using the amber bottle for MPB.

Any body can share the experience on this?

Thank you thank you!

According to my solvent guide handbook, THF absorbance begins to increase just below 280 nm. If you are running at a high sensitivity, I would expect to see some upwards baseline drift.

Noob question. Are you sure you can use THF with your type of HPLC?
There are some problems with compatibility of THF and stainless steel capillaries.
And may be THF must be filtered before using.
I'm not strong in this question, so don't beat me for my question

Noob question. Are you sure you can use THF with your type of HPLC?
There are some problems with compatibility of THF and stainless steel capillaries.
And may be THF must be filtered before using.
I'm not strong in this question, so don't beat me for my question

Using THF with stainless steel is not a problem. Pure THF will cause PEEK to swell and perhaps fail (its failure pressure is lower with THF) so mixtures of THF and another organic solvent are common. I have not heard that THF must be filtered prior to use. In fact, if you use a high quality HPLC grade solvent its recommended that you do not filter pure solvents since you'll likely add more than you remove. Some seal materials (UHMWPE) also swell with THF reducing their lifetime.

As for the increase in UV signal with increased %THF, how much of an increase are you seeing (mAU)? Are you using a DAD? If so, what is the detector bandwidth?