2018 Volume 67 Issue 1 Pages 11-17
Multiphoton ionization time-of-flight mass spectrometry (MPI-TOFMS) was applied to the measurement of toluene oil-in-water (O/W) emulsions prepared via shirasu porous glass (SPG) membrane emulsification. In the present study, the relationship between small oil droplets introduced into TOFMS and obtained signals was discussed. In the case of a toluene O/W emulsion prepared by a SPG membrane with a pore size of 1 μm, the flow of oil droplets could not be confirmed. Moreover, no spikes were observed on the time profile of the peak area for toluene obtained by MPI-TOFMS. In the case of an O/W emulsion prepared by a SPG membrane with a pore size of 3 μm, oil droplets with a diameter of ca. 12 μm, in addition to droplets of various sizes, were intermittently introduced. Moreover, a lot of spikes were detected on the time profile of the peak area obtained by MPI-TOFMS. In the case of an O/W emulsion prepared by a SPG membrane with a pore size of 5 μm, larger droplets and their aggregates were introduced. Intense spikes were detected on the time profile in the early stage of the measurement, but the number and the intensity of spikes decreased with time due to creaming of the sample. In addition, the minimum diameter of a droplet that produces a detectable spike was calculated to be 3.4 μm in the present study.
