Analytical performance of a venturi device integrated into an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer for analysis of nucleic acids

A voltage-assisted venturi device modeled after an industrial air amplifier was used to improve the ion transmission efficiency of a 16.2 kDa oligonucleotide and a 53mer PCR product in the high-pressure region between an electrospray ionization (ESI) emitter and the sampling orifices of two Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR-MS). The venturi device increased the total ion abundance of the oligonucleotide and the PCR product by more than 6-fold relative to the best achievable signal without the device. Furthermore, the average charge states of the oligonucleotide and PCR product shifted from 12.5- to 14.5- and 10.9- to 12.6-, respectively, with the addition of the venturi device. Specific to FT-ICR mass spectrometry, this increase in the charge state directly translates to an increase in theoretical mass resolving power ( > 10 000 full width half-maximum for the results presented here at 7 T). Adduction was still observed while using the device, suggesting that it is "soft" relative to other high-pressure ion focusing methods.