Different mass spectra on different instruments - why?

[bunnahabhain]

Hi everybody

Please have a look at these two spectra, recorded by direct infusion (substance in MeOH, 10 µl/min direct infusion) in two different instrument:
First is a Micromass Quattro Ultima Pt set to ES+, 4.5 kV needle and 150 V cone, second is a Thermo MSQ set to ESI+, 4.5 kv needle and 150 V cone.
Quattro Ultima:

MSQ:


I don't understand why in the MSQ spectrum I have mass 439 very abundant while it is missing completely in the Quattro Ultima spectrum. Mass 461 looks to me like proton vs. sodium exchange, but where should the sodium come from? The analyte solution for both spectra was infused from the same syringe, disconnected from one instrument and walked over to the other, no more than 5 min between measurements. Any idea?
Thanks in advance,
Jörg

BTW: M/Z 220 is the [M+H]+ I am looking for, 439 is [2M+H]+. 147 and 74 are [M+2H]2+ and [M+3H]3+, respectively.

[Tomtotom]

BTW: M/Z 220 is the [M+H]+ I am looking for, 439 is [2M+H]+. 147 and 74 are [M+2H]2+ and [M+3H]3+, respectively.

If m/z 220 is [M+H]+, than m/z 110,5 would be [M+2H]2+. Due to the m/z 147 signal it could also be that m/z 74 is [M+H]+; m/z 147 is [2M+H]+; m/z 220 is [3M+H]+ and m/z 439 is [6M+H]+.
What is your substance?

[JMB]

1. Na+ ions are derived (mostly) from glassware

2. Yes, if [M+H]+ is at m/z 220, then [M+2H]2+ would indeed be at m/z 110.5.

3. [M+H]+ IS at m/z 220.3, since [M+Na]+ is at m/z 242.3; m/z 461.6 IS [2M+Na]+.

4. The isotope peaks at m/z 221.3 and m/z 462.6 show that both ion signals are singly, not multiply, charged.

5. Different spectra largely due to different ESI source design/gas flow rates/ temp. etc.
You may sometimes change your spectrum (not the basic of it) simply by manipulating cone voltages/ source temps. etc on the SAME instrument.

[bunnahabhain]

If m/z 220 is [M+H]+, than m/z 110,5 would be [M+2H]2+. Due to the m/z 147 signal it could also be that m/z 74 is [M+H]+; m/z 147 is [2M+H]+; m/z 220 is [3M+H]+ and m/z 439 is [6M+H]+.
What is your substance?

Thank you Tomtotom
Sorry I may not give details on the substance. You are right, [M+2H]2+ must be wrong. The only other possibility is such a strange thing as [2M+3H]3+ which would result in 147.

1. Na+ ions are derived (mostly) from glassware

The solution did not touch glass between the measurements. As mentioned, it was already in the syringe, in one instrument I have only Na adduct, in the other nearly nothing of it. This is what is strange to me.
I am going to play around with temperature and gas flow some more. But any idea what the additional +12 peaks on the Quattro Ultima spectrum could be? (74+12 = 86, 147+12 = 159)

Thank you
Jörg

[LiVD]

You may be able to get rid of the Na adducts by increasing the cone gas flow.

[Peter Apps]

1. Na+ ions are derived (mostly) from glassware

The solution did not touch glass between the measurements. As mentioned, it was already in the syringe,

Thank you
Jörg

And the syringe is made of ...... ?

Peter

[JMB]

There are no +12 adducts (m/z 147/159) in mass spectrometry; it may be that m/z 74 and 147 are [M+H]+ and [2M+H]+ for a reactant in the synthesis, e.g. (C2H5)2NH.

[Tomtotom]

But any idea what the additional +12 peaks on the Quattro Ultima spectrum could be? (74+12 = 86, 147+12 = 159)

The 159 peak could be an 86-Adduct of the 74 peak. Solvents sometimes show that behaviour. The 33 signal is [Methanol+H]+. I wonder if you have Acetonitril in your sample, than 74 could be [MeOH1ACN1+H]+. For me it is interesting that there are almost no peaks between 220 and 439. It looks like a monomer, a dimer, a trimer and a hexamer. That makes solvent clusters unlikely, i guess you would also see a tetramer and a pentamer. So maybe you see reaction products, and the trimer and hexamer are stabile forms whereas the tetramer and the pentamer are not. The +12 signals may also be -X signals.

[bunnahabhain]

And the syringe is made of ...... ?
Peter

Yes, I know that the syringe is made of glass, but I do not understand why it should lose sodium to the analyte when injecting to one machine while it does not when injecting to the other machine. Same syringe, different behaviour?

The +12 signals may also be -X signals.

Yes, of course. I just don't know -what

You may be able to get rid of the Na adducts by increasing the cone gas flow.

I tried, but I didn't find a suitable setting (cone gas from zero to maximum => Only traces of +H, the +Na signal remains most intense.

Thank you everybody for the comments. I learned that I will have to play around some more.
Jörg

[Tomtotom]

The +12 signals may also be -X signals.

Yes, of course. I just don't know -what

It could also be something like addition of an ethyl group and elimination of ammonia.

[Peter Apps]

And the syringe is made of ...... ?
Peter

Yes, I know that the syringe is made of glass, but I do not understand why it should lose sodium to the analyte when injecting to one machine while it does not when injecting to the other machine. Same syringe, different behaviour?

Jörg

A likely variable is the time between loading the syringe and finishing the injection ?

Peter

[lmh]

I honestly wouldn't worry about why you get a sodium adduct (or cluster) ion in one system and not the other. Yes, sodium comes out of glassware, and that means that you could get sodium in either instrument, but whether you do or not depends not only on the chemical, but also on the source-design. Cluster ions are particularly unreliable because they're so fragile; more or less energetic sources can fragment them back to monomers. And sodium and hydrogen cluster ions will have different stability.

And on that note, could 86 be some sort of in-source fragment of one of the heavier peaks? I'm guessing the micromass is the more energetic of the two systems.