A facile approach for rapid on-site screening of nicotine in natural tobacco.

Nicotine (Nic) exposed to the environment which comes from tobacco products is the main addictive agent and specific classes of hazardous compound that merit concern. In this study, we have established a fast and reliable method to achieve specific detection of Nic in natural nicotiana tabacum within 30 s through a miniaturized platform based on screen printed gold electrode (SPE). A simple electrochemical pretreatment mean was employed on gold surface that led to the exposure of Au (111) facet and a convenient sample pretreatment method was adopted to realize the extraction of Nic in tobacco. The present electrochemical sensor exhibits an ample range of sensing from 10 µg/g to 200 µg/g, which is able to compliance with tobacco industry testing standards of actual samples. Over 60 sampling points from different origins in China or other countries were performed with direct analysis using this method and satisfactory results have been obtained. The proposed approach was demonstrated to be a very promising platform for significantly improving analytical efficiency in laboratories as well as for monitoring the source reduction control of Nic in the environment.

Development of a heart-cutting supercritical fluid chromatography-high-performance liquid chromatography coupled to tandem mass spectrometry for the determination of four tobacco-specific nitrosamines in mainstream smoke.

This paper proposed a newly developed heart-cutting two-dimensional supercritical fluid chromatography-high-performance liquid chromatography system coupled to tandem mass spectrometry (SFC-HPLC-MS/MS) for the determination of four tobacco-specific nitrosamines (TSNAs) in cigarette mainstream smoke. The orthogonality of five SFC columns and two HPLC columns was evaluated. The 1-AA column was applied for the first dimensional (1D) SFC separation to isolate the target compounds from the complex cigarette smoke matrices, and a trapping column in conjunction with an isocratic pump was employed to capture the 1D elutes. Then, the trapped 1D elutes were transferred into the C18 column through a two-position/six-port valve for the second dimensional (2D) analysis. The ion suppression was significantly reduced by the established SFC-HPLC system; meanwhile, the matrix interferences were eliminated as the results demonstrated. A dynamic range between 0.1 and 20 ng/mL was achieved with LOQs of 0.72 µg/cig for N-nitrosonornicotine (NNN), 0.66 µg/cig for nicotine-derived nitrosamine ketone (NNK), 0.81 µg/cig for N-nitrosoanatabine (NAT), and 0.39 µg/cig for N-nitrosoanabasine (NAB). All the results revealed that the presented method exhibited good repeatabilities and recoveries and could be used as a rapid and reliable approach for routine analysis of TSNAs in mainstream smoke.

Investigating the proteomic expression profile of tobacco (Nicotiana tabacum) leaves during four growth stages using the iTRAQ method.

Despite the importance of tobacco (Nicotiana tabacum) in agriculture and model organism investigations, the proteomic changes that occur in the tobacco leaf as it matures remain to be explored. In this study, an isobaric tags for relative and absolute quantification (iTRAQ) strategy was applied to investigate the proteomic profiles of K326 and Honghua Dajinyuan (HD) tobacco leaves at four growth stages. The proteomic profile varied with growth stage in both K326 and HD. Gene ontology (GO) classification was used to identify the biological processes that showed the greatest changes in protein expression between growth stages of HD and K326. Moreover, the number of differentially expressed proteins was greater in HD than in K326, especially during the rosette growth stage and the fast-growing stage. The galactose metabolism and glycosphingolipid biosynthesis-globo series pathways appeared only during the rosette growth stage of HD. It therefore appears that these pathways may be correlated with tobacco mosaic disease. The identification of these pathways should prove useful in investigations of the pathogenesis of tobacco mosaic virus. Graphical abstract ᅟ.

Separation and Analysis of Sucrose Esters in Tobacco by Online Liquid Chromatography-Gas Chromatography/Mass Spectrometry.

In this work, a strategy of in-series combination of ultrasound-assisted extraction and online LC-GC/MS was constructed for effective separation and analysis of sucrose esters in tobacco. Sucrose esters were first extracted by ultrasound-assisted extraction with high efficiency and easyhandling. Online LC-GC/MS was then applied for sucrose ester clean-up and analysis. To better evaluate the effectiveness of this strategy, we limited our focus to five groups of sucrose ester isomers. Each group differed in mass from the next by 14 Da. The obtained coefficient of the calibration curve was 0.9986. Limit of detection (LOD) and limit of quantitation (LOQ) were 0.05 and 0.16 µg/ mL, respectively. The recovery was above 90% and the reproducibility was below 4%. This strategy was subsequently applied to the comparison of relative amounts of five groups of sucrose esters extracted from three different parts of aromatic tobacco. The satisfactory performance indicated that this strategy has great prospect for the rapid and high-throughput analysis of sucrose esters in tobacco.

Development of Multiple Heart-Cutting Two-Dimensional Liquid Chromatography Coupled to Quadrupole-Orbitrap High Resolution Mass Spectrometry for Simultaneous Determination of Aflatoxin B1, B2, G1, G2, and Ochratoxin A in Snus, a Smokeless Tobacco Product.

The combination of multiple heart-cutting two-dimensional liquid chromatography (MHC-LC/LC) and quadrupole-orbitrap high-resolution mass spectrometry (HRMS) for simultaneous determination of the aflatoxins and ochratoxin A in snus is presented in this work. A C18 capillary column was used as the first dimension (1D) to isolate the aflatoxins and ochratoxin A from the complex matrices; then, a 2-position/10-port high-pressure valve equipped with two 60 µL loops was employed to transfer the heart-cuts of 1D-LC into a pentafluorophenyl (PFP) column for the second dimension (2D) separation. With the better separation of the MHC-LC/LC system, the sensitivity of the method was improved, which is essential for the trace mycotoxins analysis. Furthermore, HRMS performed in parallel reaction monitoring mode was employed to eliminate the interferences, and the sample pretreatment procedure was simplified. A new approach utilizing ethyl acetate with 1% formic acid/water solution was adopted to extract aflatoxins and ochratoxin A in snus, which provided parallel recoveries for aflatoxins and ochratoxin A with higher responses in comparison with the QuEChERS method. A dynamic range between 0.2 and 20 µg/kg was achieved with LOQs of 0.05 µg/kg for aflatoxin B1, 0.1 µg/kg for aflatoxin B2, G1, G2, and 1.0 µg/kg for ochratoxin A in dry mass of product. The results revealed that the established method exhibited good repeatability and recovery and could be used as a rapid and reliable approach for routine analysis of aflatoxins and ochratoxin A in snus.

Quantitative method for analysis of tobacco-specific N-nitrosamines in mainstream cigarette smoke by using heart-cutting two-dimensional liquid chromatography with tandem mass spectrometry.

A heart-cutting two dimensional liquid chromatography coupled with tandem mass spectrometry method was developed for the analysis of tobacco-specific N-nitrosamines (TSNAs) at low concentration level in Virginia-type cigarette smoke. A strong cation exchange column was utilized for the first dimensional separation, which effectively removed acidic and neutral components in the smoke, followed by a reversed phase liquid chromatography coupled with tandem mass spectrometric analysis. To capture components of the TSNAs in the effluent on the trapping column, a compensating pump was applied for online dilution and pH adjustment during the period of the TSNAs fraction transferring and enrichment. Highly sensitive determination of the TSNAs in mainstream cigarette smoke was achieved by isotope deuterated internal standards under the multiple reaction monitoring mode. Compared with traditional methodologies, the method was almost no matrix interference. Limits of quantity for the TSNAs were within 0.027-0.094 ng/mL, and the results showed good reproducibility and accuracy. Finally, the new method was applied for analysis of the Kentucky reference cigarettes and the results agreed well with joint experiments of Cooperation Centre for Scientific Research Relative to Tobacco.

Identifying the tobacco related free radicals by UPCC-QTOF-MS with radical trapping method in mainstream cigarette smoke.

Tobacco related free radicals (TFRs) in the cigarette smoke are specific classes of hazardous compounds that merit concern. In this study, we developed a hybrid method to identify TFRs directly based on ultra-performance convergence chromatography with a quadrupole time-of-flight mass spectrometry (UPCC-QTOF MS) combined spin trapping technique. The short-lived TFRs were stabilized successfully in situ through spin trapping procedure and UPCC was applied to facilitate efficient separation of complex derivative products. Coupling of orthogonal partial least squares discriminant analysis (OPLS-DA), UPCC-QTOF MS system enabled us to identify specific potential TFRs with exact chemical formula. Moreover, computational stimulations have been carried out to evaluate the optimized stability of TFRs. This work is a successful demonstration for the application of an advanced hyphenated technique for separation of TFRs with short detection time (less than 7min) and high throughput.

Sensitive determination of trace urinary 3-hydroxybenzo[a]pyrene using ionic liquids-based dispersive liquid-liquid microextraction followed by chemical derivatization and high performance liquid chromatography-high resolution tandem mass spectrometry.

3-Hydroxybenzo[a]pyrene (3-OHBaP) is widely used as a biomarker for assessing carcinogenic benzo[a]pyrene exposure risks. However, monitoring urinary 3-OHBaP suffers from an insufficient sensitivity due to the pg/mL level in urine excretion. In this study, a sensitive method for determination trace urinary 3-OHBaP was developed, involving enzymatic hydrolysis of the glucuronide and sulfate conjugates, ionic liquids dispersive liquid-liquid microextraction (IL-DLLME) enrichment, derivatization with dansyl chloride and HPLC-HRMS/MS analysis in the positive ion mode. Using IL-DLLME makes the enrichment of trace 3-OHBaP very simple, time-saving, efficiency and environmentally-friendly. To enhanced HPLC-HRMS/MS response, an MS-friendly dansyl group was introduced to increase the ionization and fragmentation efficiency. The optimal IL-DLLME extraction parameters and derivatization reaction conditions were investigated. Good linearity was obtained over a concentration range of 0.6-50.0pg/mL with correlation coefficients (r(2)) of 0.9918. The limit of detection (LOD) and limit of quantification (LOQ) values were 0.2pg/mL and 0.58pg/mL, respectively. The recoveries were 92.0±4.2% with the intra-day and inter-day RSD values ranged from 2.2% to 3.8% and from 3.3% to 6.8%, respectively. The proposed IL-DLLME-Dansylation-HPLC-HRMS/MS method was successfully applied to determine urinary 3-OHBaP of non-occupational exposed smokers and nonsmokers.

Tuning the adsorption behaviors of water, methanol, and ethanol in a porous material by varying the flexibility of substituted groups.

Exploring the adsorption and separation of water, methanol, and ethanol is important concerning the use of a sustainable energy source from biofuel. In this paper, the effects of the flexibility of substituted groups have been studied based on three iso-reticular metal-organic frameworks (MOFs), in which the pore surface is decorated with propargyl (-CH2-C[triple bond, length as m-dash]CH), allyl (-CH2-CH[double bond, length as m-dash]CH2), and propyl (-CH2-CH2-CH3) groups respectively. These substituted groups stretch into the channel, acting as gates, and the gate-opening for guests is controlled by the flexibility as well as host-guest interactions. Our study results indicate that (i) the adsorption capacity of water, methanol and ethanol enhances accordingly with the increase of the flexibility of substituted groups; (ii) the adsorptive discrimination of water, methanol, and ethanol on this porous sorbent could be tuned by varying the substituted groups.

Facile Synthesis of CeO2-LaFeO3 Perovskite Composite and Its Application for 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanone (NNK) Degradation.

A facile and environmentally friendly surface-ion adsorption method using CeCO3OH@C as template was demonstrated to synthesize CeO2-LaFeO3 perovskite composite material. The obtained composite was characterized by X-ray diffraction (XRD), fourier transform infrared spectra (FT-IR), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC), N2 adsorption/desorption isotherms and X-ray photoelectron spectra (XPS) measurements. The catalytic degradation of nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was tested to evaluate catalytic activity of the CeO2-LaFeO3 composite. Much better activity was observed for the CeO2-LaFeO3 composite comparing with CeO2 and LaFeO3. These results suggested that perovskite composite materials are a promising candidate for the degradation of tobacco-specific nitrosamines (TSNAs).

Synthesis of divinylbenzene polymer/Fe3O4 hybrid monolithic column for enrichment and online thermal desorption of methylmercury in real samples.

A novel method of divinylbenzene polymer (DVB)/Fe3O4 hybrid monolithic column solid phase extraction and on line thermal desorption was developed to analyze methylmercury (MeHg) in water and fish samples. The monolithic column was prepared by in situ polymerization in silica tube and its heating characteristic was studied in detail. Special accent was put on the study of parameters influencing adsorption and desorption of MeHg, such as pH, flow rate of sample solution, temperature of desorption and flow rate of carrier. Under optimum conditions, the detection limit and relative standard deviation of MeHg were 0.09 ng L(-1) and 2.6% (10 ng L(-1), N=11), respectively. Recoveries of MeHg were never less than 96%. Standard reference material GBW10029 was analyzed for validation of the methodology. This method was successfully applied to the determination of MeHg in water and fish samples.

A novel fully automated on-line coupled liquid chromatography-gas chromatography technique used for the determination of organochlorine pesticide residues in tobacco and tobacco products.

In this study, a novel fully automated on-line coupled liquid chromatography-gas chromatography (LC-GC) technique was reported and applied for the determination of organochlorine pesticide residues (OCPs) in tobacco and tobacco products. Using a switching valve to isolate the capillary pre-column and the analytical column during the solvent evaporation period, the LC solvent can be completely removed and prevented from reaching the GC column and the detector. The established method was used to determinate the OCPs in tobacco samples. By using Florisil SPE column and employing GPC technique, polarity impurities and large molecule impurities were removed. A dynamic range 1-100ng/mL was achieved with detection limits from 1.5 to 3.3µg/kg. The method exhibited good repeatability and recoveries. This technology may provide an alternative way for trace analysis of complex samples.

Preparation of phenyl group-functionalized magnetic mesoporous silica microspheres for fast extraction and analysis of acetaldehyde in mainstream cigarette smoke by gas chromatography-mass spectrometry.

Acetaldehyde is regarded as a toxic mainstream cigarette smoke constituent, and measurement of acetaldehyde in complex real samples is difficult owing to its high volatility and reactivity. In this work, phenyl group-functionalized magnetic mesoporous microspheres were developed as the solid-phase extraction sorbents for enrichment and analysis of acetaldehyde in mainstream cigarette smoke. The functional magnetic microspheres were first synthesized through a facile one-pot co-condensation approach. The prepared nanomaterials possessed abundant silanol groups in the exterior surface and numerous phenyl groups in the interior pore-walls, as well as a large surface area (273.5m(2)/g), strong superparamagnetism and uniform mesopores (3.3 nm). Acetaldehyde in mainstream cigarette smoke was collected in water and derivatizated with O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine. The formed acetaldehyde oximes were extracted and enriched by the prepared adsorbents via π-π interactions and subsequently analyzed using GC-MS. Extraction conditions such as amounts of sorbents, eluting solvent, adsorption and desorption time were investigated and optimized to achieve the best efficiency. Method validations including linearity, recovery, repeatability, and limit of detection were also studied. It was found that the suggested methodology provided low detection limit of 0.04 mg/mL, good recovery of 88-92%, intra-day and inter-day RSD values of 4.5% and 10.1%, and linear range of 0.25-4 mg/mL (R(2)=0.999). The results indicated that the proposed method based on phenyl-functionalized magnetic mesoporous microspheres was rapid, efficient and convenient for the enrichment and analysis of acetaldehyde in tobacco.

Development of a rapid method for the simultaneous separation and determination of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its N- and O-glucuronides in human urine by liquid chromatography-tandem mass spectrometry.

Determination of the tobacco-specific nitrosamine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its N- and O-glucuronides (NNAL-N-Gluc and NNAL-O-Gluc) is important for toxicology analysis of tobacco smoke induced carcinogenicity and the understanding of detoxification mechanisms of the carcinogenic nitrosamine in humans. But previously reported indirect measurement methods involving enzymolysis and base treatment steps were tedious and time-consuming. In this work, a direct measurement method for simultaneous determination of urinary NNAL, NNAL-N-Gluc and NNAL-O-Gluc by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a single run was developed for the first time without the need to perform enzymatic or base hydrolysis. Urine samples were purified using dichloromethane and further extracted by solid-phase extraction. Then they were analyzed by LC-MS/MS operated in electrospray positive ionization mode. Chromatographic separation was achieved on a Phenomenex Kinetex PFP column within 6 min. The proposed method was validated and the results demonstrated that the method can produce satisfactory recoveries and reproducibility for the analytes. The applicability of this newly developed method was investigated for the simultaneous analysis of the three metabolites in smokers' urine and the obtained results were comparable to those detected using the conventional enzymolysis method.

Development of solvent micro-extraction combined with derivatization.

Solvent microextraction (SME), such as single-drop microextraction (SDME), hollow-fiber liquid-phase microextraction (HF-LPME) and dispersive liquid-liquid microextraction (DLLME), has been explored for its ability to cover a wide range of analytes. Microextraction, combined microextraction with derivatization can greatly improve separation, detectability and compound identification, expand its scope of application, and improve the effect of analysis. In this view, the article not only highlights the development of the microextraction technology such as SDBE, HF-LPME and DLLME, but also improves the key strategies of microextraction coupled to derivatization in analytical chemistry. In order to encourage further development of microextraction-derivatization, its coupling with different analytical techniques such as GC or GC-MS, HPLC, and the other technique has also been discussed.

Surface properties of solid materials measured by modified inverse gas chromatography.

A novel modified inverse gas chromatography (IGC) method has been developed to investigate the surface properties of solid materials. On the modified IGC system, the every adjusted retention time of miscellaneous probe molecules can be rapidly calculated within only one sample injection through wisely induction a capillary column and two detectors, i.e., flame ionization detector (FID) and thermal conductivity detector (TCD). In the system, the relative dead time can be acquired from FID detector while the retention time can be obtained from TCD detector simultaneously. The significant advantage of our design is that, experimental time is greatly saved compared to the traditional IGC. In addition, the new system is capable of distinguishing variety surface properties of porous materials. Two types of active carbon samples were tested, and the results showed that their thermodynamic parameters were quite different, indicating that the samples have opposite acidic/basic properties. The use of IGC would be an effective tool to evaluate the physiochemical data of solid materials.

Preparation and characterization of organic-functionalized mesoporous silica as heavy metal adsorbents.

Novel organic-inorganic hybrid mesoporous materials have attracted much attention because the functional organic groups can bring these materials special properties, such as selective absorption and new catalytic properties. In this paper, two kind of bis(triethoxysilyl) organic skeleton (EtO)3Si-(CH2)3-NH-C(O)-X-C(O)-NH-(CH2)3-Si(OEt)3 (X = 1,4-benzene (BSPB), 2,5-thienyl (BSPT)) precursors were synthesized firstly. Then bridged organic-inorganic hybrid mesoporous materials were prepared by direct grafting on MCM-41. The MCM-41 was obtained under basic conditions using cetyltrimethylammonium bromide (CTAB) as a template with tetraethyl orthosilicate. FT-IR spectra showed the acylamino, carbonyl, phenyl and thienyl groups had been introduced into the materials. The structures of these materials were further confirmed by X-ray diffraction (XRD) and the N2 adsorption-desorption. In addition, the adsorption capacity of heavy metal ions such as mercury, cadmium, and lead, was evaluated. The results indicated that the functionalized mesoporous materials with high porosity and specific surface area were successfully prepared, and the new prepared materials exhibited good adsorption capacity for heavy metal ions Hg2+, Cd2+, and Pb2+.

Analysis of amino acids in tobacco by derivatization and dispersive liquid-liquid microextraction based on solidification of floating organic droplet method.

A new one-step derivatization and microextraction technique was developed for determination of amino acids in tobacco samples. In the proposed method, amino acids were derivatized with isobutyl chloroformate (IBCF) in aqueous solution. The derivatives were extracted by dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO). Parameters affecting the extraction efficiency were investigated in detail. The optimum conditions were as follows: a mixture of 500µL acetone, containing 40µL 2-dodecanol, was rapidly injected by syringe into the 2mL water sample. After centrifugation, the 2-dodecanol droplets were floated at the top of the tube. Then, the tube was cooled in an ice bath. After 5min the solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and it was injected into a gas chromatograph for analysis. Under the optimum conditions, the limits of detection were of the order of 0.12-2.82µg/mL. The calibration curves showed good linearity over the investigated concentration range between 0.5 and 200µg/mL with a coefficient of estimation (R(2))>0.9887 for GC-MS (SIM). The proposed method is an alternative approach to the quantification of amino acids in tobacco samples.

Analysis of the volatile components emitted from cut tobacco processing by gas chromatography/mass spectrometry thermal desorption system.

A sensitive and reliable method was developed for the determination of volatile components emitted from cut tobacco processing using thermal desorption (TD) followed by gas chromatography-mass spectrometry (GC-MS). In the work, to obtain the optimal sorbent, three commercial sorbents were compared in terms of adsorption efficiency. The carbotrap 349 was found to have the best performance. The desorption conditions were also studied. Validation of the TD-GC-MS method showed good sensibility, linearity and precision. Limits of detection ranges were from 0.20 to 3.6 ng. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients relating to linearity were at least 0.9984. The analysis was reproducible, with relative standard deviation (n=8) within 6.5%. The target compound breakthrough examination showed no significant losses when about 1500 ng standards were prepared. In order to evaluate the performance of the analytical method in the volatile constituents of cut tobacco, samples were taken in industrial areas of cut tobacco processing. Recoveries ranged from 85.1% to 110% for all the compounds and good precision had been reached (RSD<13.3). The results proved that TD-GC-MS was a simple, rapid and accurate method for the analysis of volatile compounds emitted from cut tobacco drying step.

Development, validation, and application of a liquid chromatography-tandem mass spectrometry method for the determination of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in human hair.

The tobacco-specific nitrosamine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a valuable biomarker for human exposure to the carcinogenic nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in tobacco and tobacco smoke. In this work, an efficient and sensitive method for the analysis of NNAL in human hair was developed and validated. The hair sample was extracted by NaOH solution digestion, purified by C(18) solid-phase extraction (SPE) and molecularly imprinted solid-phase extraction, further enriched by reverse-phase ultrasound-assisted dispersive liquid-liquid microextraction (USA-DLLME) into 1.0 % aqueous formic acid, and finally analyzed by liquid chromatography-electrospray ionization tandem mass spectrometry. Good linearity was obtained in the range of 0.24-10.0 pg/mg hair with a correlation coefficient of 0.9982, when 150 mg hair was analyzed. The limit of detection and lower limit of quantification were 0.08 and 0.24 pg/mg hair, respectively. Accuracies determined from hair samples spiked with three different levels of NNAL ranged between 87.3 and 107.7 %. Intra- and inter-day relative standard deviations varied from 4.1 to 8.5 % and from 6.9 to 11.3 %, respectively. Under the optimized conditions, an enrichment factor of 20 was obtained. Finally, the developed method was applied for the analysis of NNAL in smokers' hair. The proposed sample preparation procedure combining selectivity of two-step SPE and enrichment of DLLME significantly improves the purification and enrichment of the analyte and should be useful to analyze NNAL in hair samples for cancer risk evaluation and cancer prevention in relation to exposure to the tobacco-specific carcinogen NNK.