Absorption-mode: the next generation of Fourier transform mass spectra.

The Fourier transform spectrum can be presented in the absorption-mode (commonly used in FT-NMR), magnitude-mode (FT-ICR), and power-mode (engineering applications). As is routinely used in FT-NMR, it is well-known that the absorption-mode display gives a much narrower peak shape which greatly improves the spectrum; recently, the successful solution of the phase equation allowed broadband phase correction which makes it possible to apply the absorption-mode routinely in FT-ICR. With the empirical evidence provided herein, it has been confirmed that in addition to the improvement on resolving power, compared to the conventional magnitude-mode, the new absorption-mode improves the signal-to-noise ratio (S/N) of a spectrum by 1.4-fold and can improve the mass accuracy up to 2-fold with no extra cost in instrumentation. Therefore, it is worthwhile to apply and promote absorption-mode in routine FT-ICR experiments.