A rapid, sensitive, and efficient ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) method has been developed to analyze polymethoxylated flavonoids (PMFs) in 14 Citrus peels, including 7 Citrus reticulata (C. reticulata) and 7 Citrus sinensis (C. sinensis). In this study, fast separation can be achieved within 12 min and 42 PMFs have been identified including 33 flavones and 9 flavanones. Most C. reticulata were shown to contain more than 20 PMFs, except Guangxihongpisuanju (GX) containing only 12 PMFs, while most C. sinensis contained fewer than 20 PMFs, except Edangan (EG) containing as many as 32 PMFs. To our knowledge, there are few reports about the quantitation of PMFs using the MS response. Here, a MS quantitative method was established and systematically validated in linearity, precision, and recovery. The linearity was from 1.25 ng/mL to 1.0 μg/mL with the limit of detection (LOD) as low as 75 pg/mL and the limit of quantitation (LOQ) as low as 0.25 ng/mL. Up to 13 PMFs, more types than ever before, were undoubtedly identified and quantitated according to the PMF standards. The results showed that the contents of PMFs in the C. reticulata were generally higher than those in the C. sinensis. This study is systematic for analyzing PMFs and is of great significance because it can provide guidance on utilization of both PMFs and citrus germplasm resources in the future.

An efficient ultra high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was developed for separation and profiling of phytochemical constituents of Chinese wild mandarin Mangshanju (Citrus reticulata Blanco). All constituents were well separated within 16 min. Based on retention times, accurate mass, MS fragments, and/or reference standards as well as databases, a total of 81 compounds were unambiguously identified or tentatively assigned including flavonoid glycosides, acylated flavonoid glycosides, flavones, polymethoxylated flavonoids, and limonoids as well as four other compounds. Among them, 22 polymethoxylated flavones and ten polymethoxylated flavanones/chalcones were identified in Mangshanju, more types than other citrus reported before. A basic procedure for identifying flavonoid-O-glycosides and the aglycones including polymethoxylated flavonoids was proposed. In addition, this method was successfully used to analyze another four mandarin germplasms, Cenxi suan ju, Xipi gousi gan, Nanfeng miju, and Or, showing that Mangshanju contained two characteristic compounds distinct from the other four citrus species. This study systematically profiled phytochemical constituents of Mangshanju, which was helpful for further utilization of Mangshanju owing to its abundant bioactive compounds.

GaN‐containing titanosilicate catalysts were used for the first time for the oxidative dehydrogenation (ODH) of n‐butane at a relatively low reaction temperature (460 °C). Commercially available GaN powder with a wurtzite crystal structure showed superior reactivity and stability for the ODH of n‐butane. The catalytic property of GaN catalyst for ODH strongly depends on the GaN particle size. The effects of the GaN weight percentage and GaN particle size on the catalytic performance are investigated in a fixed bed reactor. Based on the physicochemical properties of the catalyst characterized via TEM, DLS, N2 adsorption‐desorption, XRF, O2‐TPD, XRD, XPS, and in‐situ FTIR, the textural and structural properties of catalyst were obtained. The catalytic results reveal that the presence of GaN increases the activity of the catalysts, indicating that GaN can be used as a new active phase for the ODH of n‐butane. XRD, XPS, O2‐TPD, DLS, TEM, and in‐situ FTIR results show that activated O species exist on the surface of the GaN catalyst and enhance the catalytic performance with a decreasing GaN particle size, suggesting that smaller GaN particles possess a remarkable capability to activate O species in O2 and C‐H bonds in light alkanes.

Vanadium-containing titanosilicates and V-containing SBA-15 catalysts for oxidative dehydrogenation (ODH) of n-butane at lower temperatures and with lower vanadia contents were contrastively studied. The catalysts were investigated by various techniques, namely, N2 adsorption–desorption, SAXS, TEM, FT-IR, XRD, XRF, H2-TPR, O2-TPD, and XPS, in relation to their performance for the ODH of n-butane. Results reveal that titanosilicate materials synthesized exhibit mesoporous structure, high BET specific surface area, and high total pore volume. H2-TPR, O2-TPD, and XPS results show that lattice oxygen exists in the surface of the V-containing titanosilicate catalysts and enhances the reducibility of vanadia-based catalysts with increasing TiO2 loadings. The V-containing titanosilicate catalysts exhibit much higher catalytic activity for the ODH of n-butane than that of V-containing SBA-15 at a significantly lower temperature of 460 °C, which indicates that lattice oxygen in the catalyst plays an important role in the activation of n-butane.

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