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Paper-capillary spray modified on the basis of paper spray ionization in order to facilitate the combination with portable mass spectrometry is an ambient ionization technique, which can be uesd to detect compounds rapidly without the restriction of location and environment. Paper-capillary spray and ambient ionization portable mass spectrometry in positive ion mode were used to collect mass spectrum information of 40 kinds of cathinones controlled in China. The ［M+H］+ peak of MS1, the characteristic fragment ions of MS2 and MS2_DDA mode and their relative abundance ratio were analyzed. The obtained mass spectrum information was used to establish a database for the rapid screening of 40 cathinones. It was found that C—N cleavage at the α site existed in all the cathinones through the study of their fragmentation characteristics. Whether the highest ion peak was ［M—H2O+H］+ fragment peak could infer the existence of secondary and tertiary amine structures. A series of characteristic peaks of m/z 98+CnH2n would exist when the N was substituted by pyrrolidinyl. The characteristic ion of ［M+H］+ lost 48 u or that of non ［M+H］+ lost 30 u would exist when the benzene ring was substituted by methylenedioxy. The fragmentation characteristics were studied to design and establish a complete analysis strategy for the unknown cathinones. The strategy could be applied in the following three aspects. 1) To judge whether they are cathinones; 2) To judge whether they are 40 kinds of cathinones in the database; 3) To infer the characteristic structure of cathinones outside the scope of the database. The strategy was successfully used for the structural identification of 10 analytes, which included the common categories of drugs controlled in China. No interference or misjudgment was found, and the database could be used normally. The structures inferred by the analysis strategy were consistent with the actual structure, and the isomers involved would also be distinguished because of their different fragment ions, indicating that this scheme was feasible. This method only needs simple sample loading operation and integrated small mass spectrometer, and is not limited by location and environment. In the investigation of such drug cases, this method can carry out rapid screening and timely feedback, which plays an important role in the rapid and accurate crackdown on the crime of cathinones and it is expected to be a new way to study and judge the crime of cathinones. [ABSTRACT FROM AUTHOR]

• Synthesis of novel switchable surfactants using carbon dioxide as a "switch". • CO 2 /N 2 switchable Gemini surfactants had excellent reversibility and reproducibility. • Tertiary amine structure compounds are easy to recover from water. • Understanding the "on-off" process of synthetic surfactants through DPD simulations. Conventional surfactants have excellent performance but not easily recycled and sustainable. The CO 2 /N 2 switchable Gemini surfactants can be reused while maintaining performance and can also effectively utilize greenhouse gas CO 2 , thereby reducing carbon emissions. In our work, three tertiary amines N, N'-dimethyl N, N'-dialkyl ethylenediamine with different hydrophobic chain lengths (C n DEs, n = 12, 14, and 16) were fabricated by a two-step process using alkyl bromide, ethylenediamine, formic acid, and formaldehyde as raw materials. Structures of intermediates and end products were characterized by FTIR and 1H NMR. The Gemini surfactants such as N,N′-dimethyl N,N′-bis (dodecane, tetradecane, and hexadecane) alkylethylenediamine bicarbonates (C n DBs, n = 12, 14, and 16) were generated by the synthetic corresponding tertiary amines after bubbling CO 2. After bubbling N 2 , the bicarbonate surfactants were converted into tertiary amine non-surfactants again. The reversibility of the switching of three surfactants was verified by measuring the changes in surface tension, zeta potential, particle size distribution, and foaming volume before and after CO 2 /N 2 bubbled into the tertiary amine solutions. The physicochemical properties of C n DBs were studied by thermogravimetric analysis, surface tension measurement, cation content measurement, and dissipative particle dynamics (DPD). The results demonstrated that the synthesized CO 2 /N 2 switchable Gemini surfactants had excellent reversibility and reproducibility. The application properties indicated that the Gemini surfactants could reduce interfacial tension of oil/water to ultra-low value; possessed good cation conversion rate and decent foaming properties. Furthermore, the surfactant performances were verified through DPD simulation experiments. With the industrialization of synthetic technology, the costs of CO 2 /N 2 switchable Gemini surfactants will effectively decrease. Storage and utilization of considerable quantities carbon dioxide promote our green low-carbon life, which are conducive to the achievement of the national strategic goal of China's carbon peak in 2035 and carbon neutralization in 2050. [ABSTRACT FROM AUTHOR]