Hydrothermal carbonization of cellulose was examined at 240 ℃ for 1 h. Ammonium sulfate and thiourea were selected as the doping sources of inorganic nitrogen and organic nitrogen for the preparation of supercapacitor carbon. The effect of boric acid on the properties of the resulting hydrochar after KOH activation was examined. The results showed that the proportion of functional groups and the specific surface area of the activated hydrochar would be reduced after the addition of boric acid, and the pore-forming process of the micropores would be inhibited. The hydrochar obtained from the reaction of cellulose and organic nitrogen compounds had better pore size distribution and electrochemical properties after activation. The largest specific surface area (952.27 m2 g-1) was obtained when only thiourea was used as the only doping source. In the three-electrode system, the specific capacitance resulting activated hydrochar reached 236.25 F g-1 at a current density of 1 A g-1. After 20,000 cycles of charging and discharging at a current density of 10 A g-1, the capacitance retention rate reached 99.96%. Therefore, this study proves that the supercapacitor carbon with good electrochemical properties could be obtained by the direct reaction of cellulose with organic nitrogen compounds.

Volatile flavor compounds play vital roles when evaluating the flavor and quality of tobacco products. Pretreatment is always required owing to the wide range of flavor compounds and the complexity of the tobacco matrix. Solvent extraction （SE）， steam distillation （SD）， simultaneous distillation extraction （SDE）， supercritical fluid extraction （SFE）， and solid phase microextraction （SPME） are methods commonly used to extract and purify volatile flavor compounds. Among these methods， SPME coupled with headspace （HS） sampling has gained considerable attention in a variety of research fields because it combines sampling， extraction， concentration， and sample injection into a single procedure to deliver advantages that include convenient and simple sample preparation， small sample volumes， high sensitivities， and convenient operation.In this study， HS-SPME coupled with gas chromatography-mass spectrometry （GC-MS） was used to analyze the volatile aroma components in tobacco leaves. First， extraction efficiency was optimized by carefully evaluating multiple parameters， including types of solid phase microextraction fibers， extraction temperature， adsorption time， and desorption time. The number of chromatographic peaks， total chromatographic peak area， number of identified compounds， and internal-standard peak areas were used as indices. The optimized protocol involves incubating tobacco powder （1.0 g） under 80 ℃， extraction with an 80 μm divinylbenzene/carboxen/polydimethylsiloxane （DVB/CWR/PDMS） SPME needle for 30 min， followed by desorption from the fiber for a sufficient time （8 min）. These conditions led to a 1.6% RSD for the internal-standard peak area across five replicate experiments； hence， the developed method is highly repeatable. The volatile aroma components in tobacco leaves obtained from five different production areas were analyzed using the optimized parameters. A total of 107 volatile aroma compounds were identified， among which ketones， aromatics， and heterocyclic compounds accounted for more than 70% of the total volatile aroma components （excluding neophytadiene）. Tobacco leaves obtained from the Shangluo region contained the highest amount of total volatile aroma compounds， followed by leaves from Ankang， Hanzhong， Baoji， and Yan’an regions. Orthogonal partial least squares-discriminant analysis （OPLS-DA） was used to determine the main differential components from the various production regions， which identified 14 differential compounds （primarily ketones and alcohols）. This study provides a theoretical basis and reference for further exploring key volatile flavor compounds in leaves sourced from different production areas， as well as for identifying flavor-indicator substances and improving the quality of tobacco leaves.

A novel MG/MPS derivatization strategy is established for highly specific and sensitive analysis of protein citrullination by mass spectrometry.