A Quantitative Analysis of an Oil Component in an Emulsion by Multiphoton Ionization Mass Spectrometry

The first quantitative analysis of an oil component in an emulsion was achieved by multiphoton ionization time-of-flight mass spectrometry (MPI-TOFMS). An oil-in-water (O/W) emulsion was prepared. Styrene (0 - 5000 ng μL^-1) and Triton X-100 were used as the oil phase and the disperser, respectively. Toluene was employed as an internal standard. We obtained a series of mass spectra, and then constructed the time profiles for styrene and toluene. As a result, we found several spikes from both time profiles when measuring emulsions with higher concentrations of styrene. Moreover, the timing of spikes for toluene coincided with that of styrene. These results suggested the movement of toluene into styrene droplets in the prepared emulsion. Furthermore, we constructed calibration curves of styrene using both the absolute calibration curve method and an internal standard method. Linear calibration curves were obtained in the concentration range investigated in the present study; the coefficients of determination obtained by both methods were 0.9956 and 0.9986, respectively.