In this study, a high-throughput and high-sensitivity profiling system for β-cryptoxanthin (βCX) and β-cryptoxanthin fatty acid ester (βCXFA) was constructed by supercritical fluid chromatography (SFC) coupled with triple quadrupole mass spectrometry (QqQMS). βCX and nine βCXFAs were successfully separated within 20 min using a column packed with octadecylsilyl-bonded silica particles. The limit of detection was 540 fmol for the free form and 32-130 fmol for the esterified forms. These results demonstrate that both the throughput and the sensitivity of this SFC-QqQMS system are considerably higher than those of conventional methods. When this system was applied for the analysis of Citrus unshiu, βCX and five βCXFAs were directly detected with much simpler sample pre-preparation. The analysis of other citrus fruits indicated that the βCXFA profiles varied with their breed variety. Furthermore, gas chromatography-mass spectrometry was used to analyze total fatty acid profiles in C. unshiu, and the results revealed that the profiles of fatty acids located in βCXFA were distinct. This is the first report on the analysis of βCX and its fatty acid derivatives by SFC-QqQMS. The profiling system developed in this study will be a powerful tool for investigating xanthophyll fatty acid esters.
Dark current analysis to estimate the current density of the field-emitted electrons have been developed for the prediction of the yoltage holding capability of multi-aperture multi-grid accelerators used in JT-60SA and ITER neutral beam injectors. From the experimental measurement of the field-emitted electrons in multi-aperture multi-grid accelerators, βE BD , which represent the critical current density to trigger the breakdown, were found to be constant with around 6 × 10 3 kV/mm regardless of the electric field profiles and the surface conditions in an accelerator with a surface area of 0.1 m 2. In addition, the dark current was measured in the region with the electric field above ∼60% of the electric field at the breakdown, which leads to the determination of the emission region in the analytical estimation of the dark current. Furthermore, from the measurement of βE BD on electrodes with various surface area, βE BD was found to decreases with an increase of the surface area S (βE BD = 4 × 10 3 S −0.3). From these results, the dark current profile at the critical current density can be estimated from the electric field analysis, which leads to the development of the breakdown model and the prediction of the voltage holding capability on the multi-aperture multi-grid accelerators.
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