In this study, we used a quantitative analytical method to indicate creaming behavior in an emulsion. An oil-in-water emulsion was directly measured by resonance-enhanced multiphoton ionization time-of-flight mass spectrometry, and the time profiles of the peak areas of an oil component, styrene, were obtained at heights of 1, 2, and 3 cm from the bottom of a sample that had a height of 4 cm. All time profiles roughly indicated that the signal intensity increased once, then decreased, and finally settled. Moreover, we proposed a fitting equation for the time profiles by subtracting two sigmoid functions, whereby the degree of the signal increases at the initial stage, the degree of the signal decreases after the increase, and the times for continuing the higher signal intensities were all longer as the monitoring positions were raised. This method would surely provide useful information about emulsions that undergo creaming behavior.

The fragmentation of the cluster ion, [A1῎HCl῎A2῎H] ῌ of amine bases A1 and A2, is studied by the BEBE type tandem mass spectrometer. The cluster ion, [A1῎HCl῎A2῎H] ῌ , is generated by the fast atom bombardment (FAB) ionization of mixture of two hydrochlorides of amines. The precursor ion is selected by the first analyzer (BE) and the product ions are scanned by the second analyzer (B/E linked scanning). ῌ are found to be related to their relative proton a$nities and are used to determine the proton a$nities (PAs) of methamphetamine and its analogs. The PA of methamphetamine is estimated to be 965 kJ/mol. IntroductionMethamphetamine is the most commonly abused of this class of drugs in both the United States and Japan. In some European countries there is a greater problem with abuse of amphetamine and/or the synthetic analogs: 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), and 3,4-methylenedioxy-N-ethylamphetamine (MDEA), they are often seized by the law enforcement agencies in Japan these days.Mass spectrometry, and in particular gas chromatography/mass spectrometry (GC/MS), is being extensively used for the detection and analysis of drugs of abuse and their metabolites in body fluids. The ionization method for GC/MS is mostly electron ionization (EI), however, chemical ionization (CI) is often used to confirm the molecular weight. In recent years, liquid chromatography/mass spectrometry (LC/MS) using atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI) method has become one of the important techniques for trace analysis of drugs of abuse. In CI, APCI, and even in ESI, analyte charging in the gas phase occurs through gas-phase protontransfer reactions. Therefore, the measurements of proton a$nity (PA) values of drugs of abuse seem to be more interesting. The proton a$nities (PAs) of many compounds have been measured and reported. 1), 2) Cardoso et al. recently reported the PAs of some phenylalk- ῌῌ910῍8507 3῍9῍1῍Natural Science Education Laboratory, Faculty of Education and Regional Studies, Fukui University (3῍9῍1 Bunkyo, Fukui 910῍8507, Japan) ylamines.3) However, the PAs of drugs of abuse are not reported yet as far as we know.The kinetic method developed by Cooks et al. is used to determine the PA values of various compounds. 3)῍10)In the kinetic method, the relative abundance of experiments were obtained in the third field-free region of the instrument. All samples (hydrochlorides unless Fig. 1. FAB mass spectrum of the mixture of methylamine (A1) and ethylamine (A2). Fig. 2. MI spectra (A) and CAD spectra (B) of [A1ῌHClῌA2ῌH]ῌ ions from the mixture of (a) methylamine (A1) and ethylamine (A2), (b) ethylamine (A1) and n-butylamine (A2), (c) dimethylamine (A1) and trimethylamine (A2), and (d) diethylamine (A1) and triethylamine (A2). The Fragmentation of [M 1ῌHClῌM2ῌH]ῌ (M1, M2῍Amines) ῌ from the mixture of methamphetamine (A1) and reference bases (A2). Fig. 4. MI spectra (A) and CAD spectra (B) of [A1ῌHClῌA2ῌH]ῌ ions from the mixture of (a) 2-...

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The creaming behavior of an oil-in-water (O/W) emulsion was quantitatively evaluated via resonance-enhanced multiphoton ionization time-of-flight mass spectrometry. Styrene O/W emulsions were prepared with initial styrene concentrations of 1 and 4 g/L, and the height at the center of the sample was monitored. A peak area of the molecular ion of styrene was set as the signal intensity, for which a time profile was constructed from a series of mass spectra. As a result, the averaged time profiles showed that the signal intensities increased once and then decreased with the onset of creaming. In addition, in order to fit an experimentally obtained time profile, a modified fit function was proposed. Based on the fit results, the ratios of the increases and decreases in signal intensities were different between the two emulsions-higher in the case of an O/W emulsion with a higher initial oil concentration. On the other hand, the duration of the enhancement of the signal intensity with the onset of creaming was independent of the initial oil concentration. The present method offers the possibility to quantitatively evaluate the creaming behavior of an emulsion without pretreatment, and, therefore, would be useful for confirming the stability and quality assurance of emulsions.