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"Tobacco-free" or synthetic nicotine products have been favored by the majority of young people, which undoubtedly increase the potential health risks and regulatory challenges. Currently, there are few reliable methods for the determination of authenticity of natural nicotine and synthetic nicotine. The analytical techniques based on mass spectrometry have broad application prospects in component sequence analysis. structure analysis, molecular weight determination and component content determination. The synthesis processes of natural nicotine and synthetic nicotine are different, and their isotopic fractionations are also different. Here, a method of tandem mass spectrometry based on isotope model peak was developed using this feature. The source or naturalness of nicotine is verified by comparing the abundance and area ratio of [M + H]+ and [M+H+1]+ peaks of nicotine, and the abundance ratio of [M+H]+ and [M+H+1]+ peaks as fragments of parent ions. A total of 47 experimental results showed that the m/z 164. 1. 163. 1 peak abundance ratios and the area ratios of natural nicotine and synthetic nicotine in MS spectra were significantly different. In addition, in MS/MS spectra, the abundance ratios of fragment ions of m/z 163. 1. 164. 1 also had significant differences. Among the variables with significant differences. the overall abundance ratio of synthetic nicotine was higher than that of natural nicotine. The evaluation model for the identification of natural nicotine and synthetic nicotine was further constructed by combining chemometric methods. Using OPLS-DA modeling, the discriminant accuracy was 97. 87%. Moreover, rankings of importance of variables differed depending on the model of the evaluation. 164. 1-85. 1/84. 1, 164. 1-85. 1/(84. 1+85. 1), 163. 1-131. 1/131. 1. 163. 1-131. 1/(130.1+131. 1) were the key discriminant variables. This method has the advantages of simple operation, rapid operation and no need for quantitative analysis, which will help to accurately identify, label and supervise tobacco products from different nicotine sources on the market. [ABSTRACT FROM AUTHOR]

Stable isotope ratios of carbon, nitrogen, hydrogen and oxygen act as "nature's recorder". A s a carrier for individual human information, human hair can be measured by isotope ratio mass spectrometry ORMS) to translate into information about people's dietary habits, health condition and life track. The basic principle behind establishing dietary lifestyle using isotopic profiles of human hair is the fact that the body's only source of C, N is a person's staple diet. It may have significant differences in carbon, nitrogen isotopic compositions of human hair that are living at different regions. The aim of the study was to analyze the discrepancy of 15N and 13C stable isotope ratios in human hair collected from different cities, and explore the relationship between carbon and nitrogen isotope ratios and human groups, such as gender and age. The carbon and nitrogen isotope ratios in the human hair of 247 local residents from 8 different cities were investigated by IRMS. The results showed that there were significant difference in carbon and nitrogen stable isotope ratios of human hair from different cities. The value of δ13 C was negatively correlated with vegetable consumption per capita. The value of δ15N was positively correlated with meat consumption per capita, and might be increased by high intake of fish. The relationship between δ13C, δ15N and the factors of gender and age demonstrated that there were no significant difference between males and females, but the age of females showed a weakly negative correlation with δ13 C. By comparing the data of this paper and other literatures, the carbon and nitrogen stable isotopes in the hair of residents in China were different from other countries, which implied that there were various dietary habits in different countries. [ABSTRACT FROM AUTHOR]

Inductively coupled plasma sector field mass spectrometers(ICP-SFMS) mainly include high-resolution ICP-MS (HR-ICP-MS), multi collector ICP-MS (MC-ICP-MS) and full spectrum ICP-MS. The HR-ICP-MS generally adopts the revise Nier-Johnson magnetic-electrostatic sectors double focusing geometry, the MC-ICP-MS generally adopts the forward Nier Johnson electrostatic-magnetic sectors double focusing geometry, and the full spectrum ICP-MS with detector array adopts the Mattauch-Herzog geometry. The performance improvement of ICP-SFMS is mainly reflected in the frequency turning ICP design, which improves the tolerance and reliability to the matrix, the J-type sampler cone and X-type skimmer cone are used to improve the sensitivity, the large pumping speed interface pump can reduce the vacuum in the interface area and improve the sensitivity of the instrument, and the improved ion transfer lens system can improve the abundance sensitivity of actinide isotopes. High resolution isotope ratio can be obtained by changing the slit width in front of the detectors. The use of multiple Daly detectors can improve the detection ability of low abundance isotopes. The signal output of low abundance isotope measurement can be improved by automatically switching the high resistance of Faraday cup amplifier through software. The improvement of the performance of ICP-SFMS makes it more widely used in nuclear geological analysis. In situ U-Pb dating of pitchblende micro area can be carried out by LA-HR-ICP-MS, uranium isotope fractionation can be determined with high precision by MC-ICP-MS, and refractory elements such as U, Th, Nb, Ta, Zr and Hf can be determined by LA-HR-ICP-MS. [ABSTRACT FROM AUTHOR]

In order to establish more accurately and rapid pretreatment method for the nitrogen stable isotope analysis of soil ammonium nitrogen, diffusion and N2O produced method were compared, and combined with two commercially available equipment’s, i.e., elemental analyzer-isotope ratio mass spectrometer（Flash HT-IRMS） and trace gas preconcentration-stable isotope mass spectrometry（PreCon-IRMS）, respectively, for the analysis of the nitrogen stable isotope abundance inammonium sulfate reference solutions and soil ammonium nitrogen extracted from different paddy soil samples. The stable isotope measurement results showed that both the diffusion and N2O produced method coupled IRMS analytical systems were able to provide good analytical data for ammonium sulfate reference solutions in accuracy with precision of superior to 0.5% and 0.2%, respectively. However, there was a nitrogen isotope fractionation accrued in the diffusion-treated process, and the test results needed to be corrected by a standard curve. At the same time, the 15N-stable isotope abundance in ammonium nitrogen extracted from different paddy soils were determined by diffusion and N2O produced method. The comparison of the analytical data from the two analytical methods indicated that N2O produced method coupled with PreCon-IRMS provided better nitrogen stable isotope data in reproducibility and accuracy than the data obtained by the other method. In addition, through the auxiliary automatic trace nitrogen conversion-N2O generated device, nitrogen stable isotope abundance of soil ammonium nitrogen could be simultaneously analysis online in batch process, and the pretreatment analysis time was short, the sample consumption was small, only need 10 μg N for one sample（<5 mL soil extract solution）. Therefore, for the analysis of nitrogen isotopes in micro-amounts of soil ammonium, the N2O produced method coupled with PreCon-IRMS analysis method has more advantages than the diffusion method coupled Flash HT-IRMS analysis method. [ABSTRACT FROM AUTHOR]

The stable isotope ratio in human hair can be used to trace back the spatial and temporal information of human life. The construction of a comparable database of stable isotope ratio in Chinese human hair has a great significance for forensic science research and public security investigation. However, the interference of sample pretreatment and the difference of normalization methods affected the accuracy and reproducibility of hydrogen isotope ratio measurement and made it difficult to make comparison between laboratories. This research were based on the elemental analysis-isotope ratio mass spectrometer technic (EA-IRMS), and it systematically demonstrate the selection of hydrogen isotopic reference materials and the normalization method of hydrogen isotopic compositions to isotope reference scales. Firstly, six international reference materials (USGS42, USGS43, CBS, KHS, EMAP1 and EMAP2) were selected to evaluate their suitability. Then, according to the range of δ2H values (-55‰～-80‰) of Chinese human hair measured and reported in the literatures, three of them were selected, including the minimum, maximum and middle values of the samples. Finally, by comparing the six reference materials combinations (CBS/USGS42/USGS43, CBS/USGS42/EMA-P1, CBS/USGS42/KHS, EMA-P2/USGS42/USGS43, EMA-P2/USGS42/EMA-P1 and EMA-P2/USGS42/KHS), it is proved that the standard calibration curves fitting R2 (1.000 0±0.000 0, n=4) of USGS42, USGS43 and CBS combinations are the highest, and the coefficients (1.061 8±0.006 6, n=4) of them are the most stability than other combinations by utilizing linear regression of multiple-point normalization method. At the same time, two laboratories in Beijing and Shanghai were selected to carry out 35 repeated validations. The results show that the multiple-point normalization method of the standard combination has the highest fitting degree and good stability (R2≥0.999 7, n=35). It is suitable for the normalization method of hair δ2H and can be used as a recommended method for the construction of Chinese human hair δ2H database. The idea of selecting isotopic reference materials and the normalization method of hydrogen isotopic compositions to isotope reference scales can also provide reference for the establishment of other stable isotope ratio database. [ABSTRACT FROM AUTHOR]