This work presents a new triptycene-based stationary phase (TP-PEG) combining the three-dimensional (3D) triptycene (TP) framework with polyethylene glycol (PEG) moieties for gas chromatographic (GC) separations. Its statically coated capillary column showed high column efficiency of 5263 plates/m determined by naphthalene at 120 °C. Its Rohrschneider-McReynolds constants and Abraham solvation system constants were measured to characterize its polarity and molecular interactions with analytes of different types. As evidenced, the TP-PEG column showed high-resolution performance for the isomers of anilines, phenols, halobenzenes and alkanes with distinct advantages over the PEG columns, particularly those critical isomers such as 3,5-/2,3-xylidine ( R = 2.94), m -/ p -chlorotoluene ( R = 1.92), p -/ m -cresol ( R = 1.89), 2,2-dimethylbutane/2-methylpentane ( R = 1.51), 2,2,3-trimethylbutane /2,3-dimethyl pentane ( R = 1.74) and 2,3-dimethylpentane/ n -heptane ( R = 1.92). In addition, it exhibited good column repeatability and reproducibility with the relative standard deviation (RSD) values of 0.02%–0.09% for run-to-run, 0.13%–0.22% for day-to-day and 2.7%–4.1% for column-to-column, respectively, and a wide operational temperature range (30 °C–280 °C) . Its application to GC–MS analysis of the essential oil of Osmanthus fragrans has proven its good potential for practical analysis of complex samples.
Introduction In recent years, scented black tea has attracted much attention due to its pleasant floral aroma and mellow flavor, but little research has been carried out on its flavor metabolic profile. Methods In this study, the flavor metabolic profiles of unscented, Chloranthus spicatus scented, and Osmanthus fragrans (Thunb.) Lour. scented Congou black teas were investigated using full-spectrum metabolomics analysis method, the first time that the flavor profiles of scented black tea were characterized in detail. Results and Discussion The results revealed that a total of 3,128 metabolites were detected in the three teas. Based on the criteria of variable importance in the project >1 and fold change ≥2 or ≤ 0.5, 761 non-volatile metabolites and 509 volatile metabolites were filtered as differential metabolites. Many differential non-volatile metabolites belonged to flavonoids, phenolic acids, and terpenoids. Floral, fruity and herbaceous volatile metabolites were significantly up-regulated in Chloranthus spicatus scented Congou black tea while sweet and fruity volatile metabolites were significantly down-regulated in Osmanthus fragrans (Thunb.) Lour. scented Congou black tea. The results contribute to a better understanding of the scenting techniques on the flavor quality of scented black teas and provide some information on the flavor chemistry theory of scented black teas.
Chunhe Yu,Dongmiao Qin,Xiaohua Jiang,Xiangfei Zheng,Biyang Deng
In this work, fluorescent N-doped carbon quantum dots (N-CQDs) have been synthesized by simple hydrothermal heating of natural osmanthus fragrans, without any toxic ingredients or surface chemical modifications. The N-CQDs possess a high quantum yield of 21.9 %, outstanding blue fluorescence, good water dispersity, and excellent optical stability. Because the favorable inner filter effect (IFE) between N-CQDs and quercetin (QT) occurs, the addition of QT to N-CQDs can cause their fluorescence quenching. When Al 3+ was added to the N-CQDs/QT system solution, it was found that the inhibition of IFE leads to the fluorescence intensity of N-CQDs/QT system enhancement by virtue of a specific binding of QT to aluminum ion (Al 3+ ). Therefore, we used the N-CQDs as a novel off-on fluorescent nanosensor to detect QT and Al 3+ . Under optimal conditions, the fluorescent nanosensor can detect QT within the wide linear response in the range of 0.003−80 μmol/L with as low as 1 nmol/L detection limit. For the detection of Al 3+ , the N-CQDs/QT system showed linearity response toward Al 3+ in a range of 0.1∼100 μmol/L and the limit of detection was found at 26 nmol/L. In addition, N-CQDs have been successfully used to efficient quantification QT in human plasma and monitor Al 3+ in serum samples. Noteworthy, the N-CQDs demonstrated low toxicity toward T24 cells, which realized sensing QT and Al 3+ in the living cells.
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