[Show abstract][Hide abstract] ABSTRACT: Rationale:
Tobacco-specific N-nitrosamines (TSNAs) mainly include 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), N-nitrosoanabasine (NAB) and N-nitrosoanatabine (NAT) that are formed from tobacco alkaloids during the curing process and contained in tobacco and tobacco smoke. They are linked with carcinogenesis. Analytical methods for quality control of products and determination of their metabolites are therefore of great importance.
The characteristic fragmentation behaviors of tobacco-specific TSNAs have been studied by electrospray ionization multistage tandem mass spectrometry. The deutero-labeled TSNA compounds have also been employed to clarify the fragmentation mechanism, which further confirms the proposed fragmentation patterns.
Detailed analysis of the resultant fragments shows there are two different kinds of fragmentation patterns with the general fragment backbone of pyrrolidine or piperidine rings. In one route, pyrrolidine or piperidine rings undergo direct fragmentation and form some stable intermediates without affecting the parent rings. The other, however, involves ring opening and then ring closure at the pyridine-2 carbon atom to form multi-membered rings.
This characteristic fragmentation behavior therefore provides useful information on identification of TSNAs that may be used to monitor such kinds of compound in the biological metabolism.
No preview · Article · Aug 2014 · Rapid Communications in Mass Spectrometry
[Show abstract][Hide abstract] ABSTRACT: Hydroxyl radicals (˙OH) play an important role in human diseases. Traditional detection methods are time consuming and require expensive instruments. Here, we present a simple and sensitive method for the detection of hydroxyl radicals on a microfluidic chip using an electrochemical technique. Aniline monomer is electrochemically polymerized on the surface of a pencil graphite electrode and carbonized at 800 °C. The resulting N-doped porous carbon nanofiber-modified pencil graphite electrode is embedded into a microfluidic chip directly as a working electrode. 4-Hydroxybenzoic acid (4-HBA) is selected as the trapping agent owing to its unique 3,4-DHBA product and high trapping efficiency. A low detection limit of 1.0 × 10(-6) M is achieved on the microfluidic chip. As a demonstration, the microfluidic chip is successfully utilized for the detection of ˙OH in cigarette smoke. The strong π-π stacking and hydrophobic interactions between the nitrogen-doped carbon materials and the pencil graphite make the modified electrode well-suited for the microfluidic chip.
[Show abstract][Hide abstract] ABSTRACT: A sensitive approach to the determination of reactive oxygen species (ROS) in puffs of cigarette smoke (CS) has been developed. The experimental system consists of a microfluidic chip electrophoresis and a laser induced fluorescence (LIF) device enhanced by localized surface plasmon resonance. Core-shell Ag@SiO2 nanoparticles were prepared and then immobilized on the surface of the microchannel to increase the fluorescence intensity based on localized surface plasmon resonance-enhanced fluorescence (LSPREF) effect. The ROS in puffs of CS were trapped via the oxidation of 2',7'-dichlorodihydrofluorescein (DCHF) that had been loaded on polyacrylonitrile (PAN) nanofibers in a micro-column. Determination of ROS was based on the amount of 2',7'-dichlorofluorescein (DCF), which is the sole product from DCHF oxidation. With the optimization of the trapping efficiency, we detected about 8.0 pmol of ROS per puff in the mainstream CS. This microchip electrophoresis-SPREF system enables sensitive quantitation of ROS in CS with low consumption of reagent, material, and analysis time.
[Show abstract][Hide abstract] ABSTRACT: Alkaloids are plant secondary metabolites that are widely distributed in Nicotiana species and contribute greatly to the quality of tobacco leaves. Some alkaloids, such as nornicotine and myosmine, have adverse effects on human health. To reduce the content of harmful alkaloids in tobacco leaves through conventional breeding, a genetic study of the alkaloid variation among different genotypes is required. In this study, alkaloid profiles in leaves of five Nicotiana tabacum cultivars and Nicotiana tomentosiformis were investigated. Six alkaloids were identified from all six genotypes via gas chromatograph-mass spectrometry (GC-MS). Significant differences in alkaloid content were observed both among different leaf positions and among cultivars. The contents of nornicotine and myosmine were positively and significantly correlated (R
2=0.881), and were also separated from those of other alkaloids by clustering. Thus, the genotype plays a major role in alkaloid accumulation, indicating a high potential for manipulation of alkaloid content through traditional breeding.
No preview · Article · Dec 2013 · Journal of Zhejiang University SCIENCE B
[Show abstract][Hide abstract] ABSTRACT: Pd-Cu/activated carbon catalysts were prepared by wetness impregnation and their performance in the room-temperature catalytic oxidation of the pulse reaction of carbon monoxide were investigated using simulated cigarette smoke gas consisting of 4.4 CO-4.2 H2O-19.2 O2-72.2 He (volume fraction, %). The effect of different activated carbon supports on catalytic performance was investigated in detail. The results show that at room temperature the order of catalytic performance for CO oxidation is: the catalyst supported on coconut activated carbon (CAC)2+ and Pd0 are also present on the surfaces of the CAC and WAC catalysts but only Pd2+ is present on the surface of the SAC catalysts, which results in better catalytic activity for SAC than that of the CAC and WAC catalysts. When the ternary composite filter was prepared by inserting the catalyst between the cigarette filter and the acetate filter rod, the smoking tests showed that the amount of CO in the main cigarette smoke decreased noticeably. The SAC catalyst reduced CO by 25.4% when the amount of Pd in the catalyst increased to 3.4% (w).
Full-text · Article · Mar 2011 · ACTA PHYSICO-CHIMICA SINICA
[Show abstract][Hide abstract] ABSTRACT: To investigate the cyto-genotoxicity of cigarette smoke condensates (CSCs) in human peripheral blood lymphocytes with different assays in vitro.
Human lymphocytes were exposed to particle matter of cigarette smoke combined with or without S9 mixtures at doses of 25, 50, 75, 100 and 125 microg/ml for 3 h. The cytotoxicity induced by CSCs was detected by CCK-8 assay. The DNA damage, DNA repair (repair time: 30, 60, 90, 120 and 240 min, respectively) and the somatic cell mutations induced by 75 microg/ml CSCs were measured by comet assay, hprt gene and TCR gene mutation tests, respectively.
CCK-8 assay indicated that the cell viability decreased with CSCs doses. At the doses of 100, 125 microg/ml, the cell viability of CSCs +S9 group was significantly higher than that of CSCs -S9 group (P < 0.05, P < 0.01). In comet assay, DNA damage significantly increased in a dose-dependent manner, as compared with controls (P < 0.01). Moreover, there was significant difference between -S9 group and +S9 group (P < 0.05, P < 0.01). The Mf-TCR at each dose group was significantly higher than that of controls (P < 0.05, P < 0.01). The Mf-hprt at high-dose groups were significantly higher than that of controls (P < 0.01), and significant difference of Mf-TCR and Mf-hprt at high doses of CSCs between -S9 group and +S9 group (P < 0.05, P < 0.01). The DNA damage induced by CSCs +S9 or CSCs -S9 could be repaired, but DNA repair speed was different between -S9 group and +S9 group (P < 0.05, P < 0.01).
CSCs may induce cyto-genotoxicity in human peripheral blood lymphocytes in vitro, but S9 mix could reduce the toxicity of CSCs and impact DNA repair speed.
No preview · Article · Apr 2009 · Zhonghua lao dong wei sheng zhi ye bing za zhi = Zhonghua laodong weisheng zhiyebing zazhi = Chinese journal of industrial hygiene and occupational diseases
[Show abstract][Hide abstract] ABSTRACT: N-Nnitrosodiphenylamine (NDPhA) is a typical kind of nonvolatile nitrosamine. Its electrochemical oxidation occurs usually at relative positive potentials (>1.1 V) even at catalytic noble metal electrodes in aqueous solutions. The formation of oxide and evolution of oxygen at such high potentials makes the analysis of NDPhA on noble metal electrodes difficult. Accordingly, its electrochemical analysis is usually performed in anhydrous organic electrolytes. In this work, room temperature ionic liquid [BMIM+] [BF] acting as electrolyte was introduced in this electrochemical analysis systems. It acts as supporting electrolyte itself, has good solubility of organic compounds, and allows a wide performance potential window of noble electrode, and in turn, highly electrocatalytic noble electrode of platinum or gold can be used as working electrodes. After the investigation of the electrocatalytic behavior of NDPhA at a gold electrode in this room temperature ionic liquid electrolyte, high sensitive determination of NDPhA was designed. It is demonstrated that the electrochemical response of NDPhA is determined by a surface-controlled process. Therefore, a sensor with high sensitivity was constructed by applying porous Au electrodes with highly electrocatalytic activity and large active surface area. The present approach on one hand broadens the application field of room temperature ionic liquids, and on the other hand provides a sensitive analytical method for environmental detection.
[Show abstract][Hide abstract] ABSTRACT: Generally speaking, measurement of hydroxylated radical products of salicylic acid requires a fussy separation process. In this study, we describe a simple method to electrochemically detect hydroxyl radicals (*OH) using 4-hydroxybenzoic acid (4-HBA) as the *OH trap. The *OH is generated by the Fenton reaction from iron (II) sulfate and hydrogen peroxide in a phosphate buffer solution. Experimental results show that our method can detect the OH with high sensitivity without any separation process. The differential pulse voltammetric responses show a linear dependence on the concentration of *OH in a range of 2.0x10(-6) and 1.0x10(-3)M with a determination limit down to 5.0x10(-7)M. As a demonstration, the kinetics of the Fenton reaction was mapped by measuring the reaction product of hydroxyl radical trapped by 4-HBA. The result is in good agreement with that reported previously. All the results show that the present approach could provide a simple, inexpensive and promising method for biomedicine and iatrology.