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Several smokeless tobacco products are available in the market and comprise complex chemical matrices. Sample preparation for analysis of the multiple classes of harmful compounds in smokeless tobacco products is highly cumbersome. In this study, a simultaneous extraction scheme was developed for three toxic analyte classes in smokeless tobacco products using a two‐phase solution consisting of 5% aqueous NaOH and dichloromethane in a 1:4 ratio. The dichloromethane extract was used to analyze four alkaloids directly at levels greater than parts per million; however, passing the layer through a silica cartridge for further purification and concentration was necessary for determining 18 polycyclic aromatic hydrocarbons and four volatile N‐nitrosoamines at the ppt level. The multitargets were determined by using gas chromatography with tandem mass spectrometry. The limits of detection for the 18 polycyclic aromatic hydrocarbons, four volatile N‐nitrosoamines, three minor alkaloids, and nicotine were 0.2‐1.2, 0.2‐0.4, 0.6‐1.0, and 10.2 μg/g, respectively. Four different smokeless tobacco substrates were fortified with three levels of mixed standards, and the recoveries ranged between 83 and 110%. The method was highly efficient, reduced the sample amounts, solvents, and the time required by approximately 60%. The method was used to assay 18 smokeless tobacco products, and showed potentials in assaying drugs and other plant‐based substrates. [ABSTRACT FROM AUTHOR]

Through a systematic investigation of the magnetization rotation and reversal in an exchange‐biased NiFe/MnIr film electrically detected by spin rectification effect (SRE), we experimentally demonstrate that this SRE DC voltage can be detected in the field‐swept spectra both at resonant and nonresonant conditions. The spectra show clear shifted hysteretic curves driven by exchange bias and a hysteresis loop is formed at applied magnetic field around exchanged bias field by the nonzero SRE DC voltage with sign change with the sweeping direction. More interestingly, we found that the voltage magnitude changes upon switching of magnetization can be greatly enhanced at resonance thereby suggesting an attractive approach to realize a highly sensitive method to measure exchange bias field. This experimental behavior can be interpreted within the framework of the near‐resonant spin rectification effect. [ABSTRACT FROM AUTHOR]

Amadori compounds are aroma precursors formed in the initial phase of the Maillard reaction. Based on their similar structures, simultaneous quantification of more than six Amadori compounds in tobacco has not been reported yet. In this study, a simple and rapid method was developed to simultaneously quantify ten Amadori compounds including the isomers of Fructose-isoleucine and Fructose-leucine in tobacco. The separation was performed on an Atlantis T3 column (2.1 × 250 mm, 5 μm) by gradient elution using acetonitrile and water as the mobile phases. The quantification method was systematically evaluated and proven to be sensitive and accurate. The linearity was good, with correlation coefficients of 0.9977-0.9999. The limits of detection and quantitation were 1.354-2.532 and 4.516-8.444 ng/mL, respectively. The recoveries were 84.0-119.6%, and the relative standard deviations were 1.33-5.40%. The method was used to analyze the changes in the amounts of ten Amadori compounds in tobacco before and after tobacco primary processing. The analysis shows that the Maillard reaction occurs during the short processing period. [ABSTRACT FROM AUTHOR]

A multi-pesticide residue determination method based on a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method using multiwalled carbon nanotubes as reversed-dispersive solid-phase extraction material was validated in 37 representative pesticides in tobacco. Determination was performed using liquid chromatography with tandem mass spectrometry in multiple reaction monitoring mode. Three major types of tobacco leaf samples, namely, flue-cured, burley, and oriental tobacco were studied and compared. Three factors (extraction time, external diameter, and amount of extraction material used) that could affect the performance of multi-walled carbon nanotubes were investigated. Optimization of sample preparation and determination allowed recoveries between 70.8 and 114.8% for all 37 pesticides with < 20.0% relative standard deviations at three spiking levels of 20, 50, and 200 μg/kg. The limits of quantification and limits of detection for the 37 pesticides ranged within 0.46-28.57 and 0.14-8.57 μg/kg at a signal-to-noise ratio of 10 and 3, respectively. [ABSTRACT FROM AUTHOR]

A new measurement method of a spin rectification dc voltage spectrum through fixing the magnetic field and sweeping the frequency has been proposed, which is compared to the common method to acquire a typical spectrum via sweeping an external magnetic field. Based on the shortened microstrip fixture, the measurements of rectified dc voltage as a function of frequency have been performed. From the analysis of results of the permalloy (Py) film with various thicknesses, the magnetic parameters are presented. This method can be used in samples with magnetic domains varied with respect to the external magnetic field, such as, stripe domain structures. [ABSTRACT FROM AUTHOR]