Simultaneous collision induced dissociation of the charge reduced parent ion during electron capture dissociation.

A method of performing collision induced dissociation (CID) on the charge-reduced parent ion as it is formed during electron capture dissociation (ECD), called ECD+CID, is described. In ECD+CID, the charge-reduced parent ion is selectively activated using resonant excitation and collisions with the helium bath gas inside a linear quadrupole ion trap ECD device (ECD(LIT)). It has been observed that ECD+CID can improve the sequence coverage for beta-endorphin over performing ECD alone (i.e., from 72 to 97%). Perhaps just as important, ECD+CID can be used to reduce the extent of multiple electron capture events observed when performing ECD in the ECD(LIT). Consequently, the abundance of mass-to-charge ratios corresponding to ECD product ions that contain neutralized protons is decreased, simplifying the interpretation of the product ion spectrum.

Iterative accumulation multiplexing Fourier transform ion cyclotron resonance mass spectrometry.

A multiplexed tandem mass spectrometry (MS/MS) technique known as iterative accumulation multiplexing (IAM) has been implemented on a hybrid quadrupole Fourier transform ion cyclotron resonance mass spectrometer (Q-FTICR-MS). The IAM experiment resulted in obtaining MS/MS spectra for six analytes in two MS/MS experiments while characteristic resolving power and mass measurement accuracies were maintained. Parent-product ion correlations were graphically represented in a "ratiogram" where each product ion is encoded with a ratio unique to the parent ion from which it was formed. This is the first example of multiplexed MS on a FTICR instrument where the ions are encoded externally to the ICR cell. By performing the encoding external to the ICR cell, one set of ions can be encoded while the previous set of ions is being analyzed in the cell, maximizing the use of the continuous ion current emanating from the electrospray ionization source.

Pulsed Nano-Electrospray Ionization: Characterization of Temporal Response and Implementation with a Flared Inlet Capillary.

The temporal response of pulsed nano-electrospray ionization mass spectrometry (nano-ESI-MS) was studied and its influence on ion formation and detection was characterized. Rise and decay times for the mass resolved ion current were determined to be 20 ± 3 msec and 61 ± 5 msec, respectively, which led to a maximum pulse rate of 12 Hz. Pulsed nano-ESI operation was demonstrated from a multi-sprayer source controlled by a high voltage pulsing circuit constructed in-house. The desired source mode of operation (e.g. pulsing or continuous) can be realized solely by controlling the voltage applied to each sprayer.