Contamination QTOF 6546

Hi sona ,

PEG'S are usually seen by multiple fragments with +44 m/z mass interval (which is not present here). Contamination can come from various source (mobile phase, additives, equipment use to prepare the mobile phase, etc.), but a noisy baseline can also be caused by a spluttering or inconsistent nebulizer.

To find the source of the contamination, I usually recommend to isolate each possibility. For example, if you have a syringe and a syringe motor, you could directly infuse the solvent A in the MS and see if you see the contamination. Do the same with mobile phase B, etc.. If you believe the issue comes from the sample itself, you can perform 0uL injections to see if the masses goes away.

Contamination is very often coming from mobile phase, so you can try a new bottle or a new lot of solvent to see if the contamination goes away. Same goes for additives.

Please also confirm what mobile phase you are using as mass 102.1277 m/z is often related to TEA contamination.

Regards,

Hi, philebel 

Thanks for your reply. I did the calibration and it does pass without any unwanted peaks in the spectra and since it is the same nebulizer, I can rule that possibility out. 

I do not have the syringe pump but used new solvents and I still see the contamination. 

I am using these solvents:  water ACN, and  Ammonium hydroxide, Am. bicarbonate and medronic acid as additives. 

Hi sona ,

Please compare the background you have from what you had before with the same mobile phase, project, etc.

If the noise/contamination is higher than before, this is probably coming from one of the following:  water, ACN, Ammonium hydroxide, Am. bicarbonate, medronic acid, glassware use to prepare the mobile phase, syringe or tools use to measure/take the reactive, etc.

 As mentioned above, contamination is usually caused by our mobile phase and what we use to prepare them, it only takes one step or reactive or tool that is contaminated to create issues on the MS. Finding it is often hard, that is why you need to be methodical about it and go one step at a time.

Regards,