Chromatography Forum

Hi everyone,

I have recently encountered some real issues with the baseline noise increasing on hplc system. We have had some issues with our suppliers for mobile phase and and after doing tests with the dtetector this confirms that its the mobile phase which is causing these poor baselines. Currently using Dionex ultimate 3000 Uhplc systems with the detector set at 214nm wavelength.

Does anyone have any suggestion for how the mobile phase could be prepared? We use acetonitrile buffered 4.3 pH for the method set up. It is currently prepared using the following: Dissolve 2.72 grams of sodium acetate trihydrate (NaC2H3O2.3H2O) in 500 ml of distilled water. Dilute to one litre.
Use 6.5% v/v Sulphuric Acid (H2SO4) or 1m sodium hydroxide to adjust the pH to 4.3.
Add 72 ml of Acetonitrile (CH3CN) and mix well.

What would be causing the noise and also the peaks are not the best. Any help would be appreciated and advice of better preparation of mobile phase.

Thanks

1. Use the best purity reagents you can get (but you already knew that).
2. Buy in small quantities so you don't have reagents sitting on the shelf for a long time.
3. When adjusting pH, never put the electrode in the bulk solution. Take an aliquot, measure the pH, and throw out the aliquot (pH electrodes are horrible carriers of contamination).
4. Make sure your degasser is functioning (at 214 nm you can begin to see some contribution from dissolved oxygen.
5. Thermostat/insulate your column and detector.

Acetate and 214 nm.... Good luck with the transparancy
Do a scan of your mobile phase f. x. from 200 to 300 nm and you see what I mean.

Best Regards