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The content of ethanol in wine can affect its quality. Some edible alcohol contains small amounts of methanol, and its accumulation can cause serious health problems. Therefore, it is very important to test the contents of methanol and ethanol in alcohol products. In this paper, a rapid method for the determination of methanol and ethanol by ambient corona discharge ionization mass spectrometry was developed. The method is based on the interaction of water radical cation with methanol and ethanol, respectively. In the positive ion mode, the water dimer radical cation (H2O)2+· (m/z 36) with ambient corona discharge ionization source was prepared by using ambient corona discharge ionization source, and it was introduced into the mass spectrometer with methanol or ethanol through a dual-channel low-energy corona discharge ionization device. The two reacted with each other to form the corresponding water radical cationic complex [CH3OH+H2O]+· (m/z 50) and [CH3CH2OH+H2O]+· (m/z 64), which realized the direct and rapid qualitative and quantitative analysis of methyl alcohol and ethanol in different kinds of alcoholic beverages. The result showed that the limits of detection and the limits of quantification of methanol and ethanol were 0.011 and 0.004 mg/L, 0.038 and 0.014 mg/L, respectively. The correlation coefficients of the target ionic strength curves obtained by the interaction of different concentrations of standard methanol and ethanol with water free radical cation could reach to 0.990 4 and 0.991 1, respectively. By using this method, no methanol was detected in common alcoholic drinks, and the ethanol content in liquor was higher than beer. In the actual work, the method has good practicability through the experimental exploration and verification of different wines. This method does not require sample pretreatment, has the advantages of simple operation and fast analysis, and is especially suitable for the detection of aqueous system. This study has important guiding significance for the quantitative detection and analysis of methanol and ethanol in complex system, provides technical support for the detection of alcoholic beverages and food, and also provides an effective strategy for the quantitative detection of the content of small and medium molecular alcohols in actual samples.

Microdroplets have many unique features such as small size and high electric field, therefore they can be accelerated to initiate chemical reactions and even promote some reactions that cannot be carried out in liquid phase. N, N-Dimethylaniline (DMA) is commonly used in medicine as a raw material for the synthesis of pharmaceutical intermediates. At present, the study involving in the detection of DMA is mainly focused on quantitative detection, and there is few reports on oxidation reaction and gas phase dissociation reaction of DMA. In this paper, the oxidation behavior and dissociation reaction of DMA and related compounds were studied by microdroplet spray mass spectrometry and tandem mass spectrometry. It was found that the ultra-high electric field spontaneously generated by microdroplets at the air-water interface can enable the oxidation reaction of DMA and related compounds to form abundant radical cation DMA+·. By changing the reaction distance, carrier gas pressure, injection velocity, sample concentration and substituent groups, the influence of experimental conditions and substituent modes on the generation of DMA+· was explored. The result showed that the presence of electron donor groups is benefit for the stability of radical cations. After the dissociation of DMA+·, the main product ions were generated by elimination of hydrogen radical and a successive elimination of HC≡N via methyl migration reaction. In addition, when the electron-donating CH3 group was connected with DMA, the intensity of related radical cation increased obviously, indicating that the electron-donating groups promoted the migration reaction. In conclusion, the stable transient intermediate DMA+· that is difficult to prepare by other means, was obtained by microdroplet reaction in this study. This method is helpful to deepen the understanding of the chemical promoted oxidation reaction characteristics of water droplets and enriches the rearrangement reaction types of aniline compounds in gas phase dissociation. It is expected that the prepared active species such as high reactivity radical cations will be applied to chemical industry or pharmaceutical fields in the future.

The desulfurized ground tire rubber (DGTR) was prepared from 40 mesh waste ground tire rubber by ultrasonic desulfurization process in an ultrasonic co-rotating twin- screw extruder. The effects of ultrasonic amplitude on the die pressure and power consumption during ultrasonic desulfurization process, the external morphology, rheological properties and curing characteristics of DGTR, and the mechanical properties of the re- vulcanized DGTR were studied. The results showed that with the increase in ultrasonic amplitude, the gel content, viscosity and storage modulus of the DGTR decreased gradually and loss factor increased gradually. When the ultrasonic amplitude was set as 13 μm, the number of the broken cross-linked bonds of DGTR was the largest during ultrasonic desulfurization process, which meant that the desulfurization degree of DGTR was the highest. Moreover, the tensile strength of the re-vulcanized DGTR decreased gradually and elongation at break increased gradually with the increasing ultrasonic amplitude.