Species measurements in the beam of an ionic liquid ferrofluid capillary electrospray source under magnetic stress

Three solutions of an ionic liquid ferrofluid (ILFF) using 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-NTf2) as the carrier liquid were emitted from a capillary electrospray source and the resulting beam was measured using a time-of-flight mass spectrometer (TOF-MS). The solutions had 3.04, 5.98, and 8.80 wt% iron oxide nanoparticles making them susceptible to magnetic fields. A Helmholtz coil was used to impose a gradientfree magnetic stress onto the electrospray source. Mass spectra were collected in the spray from each of the solutions, with and without the imposed magnetic field. The magnetic stress caused an increase in the peak intensity of distinct ion species (n = 0 or n = 1) at lower energy defects suggesting that the stress causes ions to be born at higher energy. The ratio of the ion peak intensity with magnetic field to ion peak intensity at zero magnetic field was proportional to the concentration of nanoparticles. The magnetic stress did not significantly affect the large mass distributions until the nanoparticle concentration reached 8.80 wt% in the fluid.