What does the "!" mean in the centroided MassLynx mass spectrum from a QTof? - WKB108561

ENVIRONMENT

• Tof (time-of-flight) instruments
• MassLynx 4.1
• MassLynx 4.2

ANSWER

The "!" means that the centroided MS peak on the MassLynx mass spectrum has a shape or resolution suggesting that interference may have occurred.
You would expect to find MS peaks flagged with an exclamation mark, "!", around the electronic noise level of a mass spectrum or a low LCMS background mass spectrum. However, it is a concern when an MS base signal, very distinctive from the electronic noise or LCMS background ions, is flagged this way.

When a true component or base signal has the ! peak flag, quite often this means that the mass spectral resolution on the peak has deteriorated. The best solution is to retune the resolution, save the settings, re-calibrate and run the acquisition again.

ADDITIONAL INFORMATION

Related KCS articles about MS peak flags:

" ? " =>    WKB4801

" ¿ " and " * " =>   WKB10187