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

Intake of tobacco nitrosamines of smokers in various provinces of China and their cancer risk: A meta-analysis

Nitrosamines are a class of carcinogens which have been detected widely in food, water, some pharmaceuticals as well as tobacco. The objectives of this paper include reviewing the basic information on tobacco consumption and nitrosamine contents, and assessing the health risks of tobacco nitrosamines exposure to Chinese smokers. We searched the publications in English from "Web of Science" and those in Chinese from the "China National Knowledge Infrastructure" in 2022 and collected 151 literatures with valid information. The content of main nitrosamines in tobacco, including 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), N-nitrosoanatabine (NAT), N-nitrosoanabasine (NAB), total tobacco-specific nitrosamines (TSNA), and N-nitrosodimethylamine (NDMA) were summarized. The information of daily tobacco consumption of smokers in 30 provinces of China was also collected. Then, the intakes of NNN, NNK, NAT, NAB, TSNAs, and NDMA via tobacco smoke were estimated as 1534 ng/day, 591 ng/day, 685 ng/day, 81 ng/day, 2543 ng/day, and 484 ng/day by adult smokers in 30 provinces, respectively. The cancer risk (CR) values for NNN and NNK inhalation intake were further calculated as 1.44 × 10-5 and 1.95 × 10-4. The CR value for NDMA intake via tobacco smoke (inhalation: 1.66 × 10-4) indicates that NDMA is similarly dangerous in tobacco smoke when compared with the TSNAs. In China, the CR values caused by average nitrosamines intake via various exposures and their order can be estimated as the following: smoke (3.75 × 10-4) > food (1.74 × 10-4) > drinking water (1.38 × 10-5). Smokers in China averagely suffer 200% of extra cancer risk caused by nitrosamines in tobacco when compared with non-smokers.

Mass spectrometry based fragmentation patterns of nitrosamine compounds

RATIONALE

Nitrosamines are a class of mutagenic substances that can display high carcinogenic potential. New chemical entities may have the potential to form unique nitrosamines specific to the drug substance. It is therefore essential to understand the gas-phase fragmentation behavior of nitrosamine compounds to enable the development of analytical methods to characterize novel nitrosamine compounds.

METHODS

The gas-phase fragmentation behavior of eight model nitrosamine compounds representing the common substructures seen in many small molecule pharmaceutical compounds was studied with positive electrospray ionization tandem mass spectrometry (ESI-MS/MS). The fragmentation patterns of these compounds under various collision parameters available in commercially available mass spectrometers were studied.

RESULTS

Protonated nitrosamine compounds produced diagnostic fragment ions upon MS/MS. Three primary structure-dependent fragmentation pathways were observed. The first pathway involves the loss of 30 Da which corresponds to the loss of the NO radical from the protonated nitrosamine compound (Group 1). The second and third fragmentation pathways, which have not been reported for nitrosamine compounds, proceed via the loss of H₂ O from the protonated nitrosamine compound (Group 2), and elimination and a loss of 46 Da (loss of NH₂ NO) from the nitrosamine compound (Group 3).

CONCLUSIONS

Results presented in this work provide an overview of the gas-phase fragmentation patterns of nitrosamine compounds and may be useful in identifying novel nitrosamine compounds in complex matrices.

Multifunctional MgO/HKUST-1 Composite for Capture, Catalysis, and Cyclic Cataluminescence Detection of Esters All-In-One to Rapidly Identify Scented Products

The integration of metallic oxide and metal-organic frameworks has attracted considerable attention as obtained composite materials because they show synergistic effects in applications of catalysis and sensing. Herein, we developed the hybrid MgO and HKUST-1 for efficient capture, catalysis, and cyclic cataluminescence (CCTL) detection of esters all-in-one to rapidly identify scented products. The multifunctional MgO/HKUST-1 composite with high CCTL activity was synthesized and characterized. The multifunctional MgO/HKUST-1 composite acts as an enrichment material for ester capture and serves as a catalyst, assisting the analyte to trigger multistage signals. The multistage signals of ester-containing scented products also satisfy the exponential decay equation with a certain τ-value. The τ-values obtained by the CCTL system were applied to identify the brands of essential oils. The working temperature served as the sensor element to obtain various τ-values. The τ-values constituted a digital code to label the different brands of cigarettes with the same aroma type. The multistage signals could be used to distinguish the origin regions of essential oils and tobacco. This work combines the CCTL strategy with the sample pretreatment, opening up a new direction to develop CCL and providing a new platform to rapidly identify ester-containing scented products.

Separation of N'-nitrosonornicotine isomers and enantiomers by supercritical fluid chromatography tandem mass spectrometry

N'-nitrosonornicotine (NNN) is one of the most prevalent and toxic tobacco-specific nitrosoamines. A chiral center at its 2'-position results in R and S enantiomers, the partial double bond character of the NN = O group also results in E and Z isomers, therefore, NNN can form a total of four absolute configurations (E-(R)-NNN, E-(S)-NNN, Z-(R)-NNN, and Z-(S)-NNN). This study investigated the resolution of R/S enantiomers and E/Z isomers of NNN by supercritical fluid chromatography tandem mass spectrometry (SFC-MS/MS). The baseline separation of E/Z-(R,S)-NNN isomers/enantiomers was accomplished through the optimization of chiral columns and co-solvents. Due to the lack of single standard of E/Z isomers, only R-NNN (sum of E-(R)-NNN and Z-(R)-NNN) and S-NNN (sum of E-(S)-NNN and Z-(S)-NNN) were further examined. Through the comprehensive optimization of SFC-MS/MS conditions, R-NNN and S-NNN were separated with a run time of 5 min, the developed method was validated, and its applicability to the determination of NNN enantiomers in burley tobacco samples was demonstrated. This study could be applied to preparative separation of single enantiomer and/or isomer of NNN, and could provide potential benefits to biologic activity studies on these enantiomers and isomers.

Determination of Methomyl Residue in Tobacco Samples by Heart-Cutting Two-Dimensional Liquid Chromatography with Tandem Mass Spectrometry

A novel heart-cutting two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) was developed for the qualitative and quantitative analysis of methomyl residue in tobacco. Compared to traditional methodologies, fairly high sensitivity and stability were achieved, and the sample procedure was simplified in the two-dimensional liquid chromatography (2D-LC) method. Although methomyl had poor retention performance in most of the reversed-phase liquid chromatography (RPLC) columns, an effective RP/RP strategy was successfully facilitated. An XB-Phenyl column was employed in the first dimension to effectively remove thousands of interference compounds in the matrix. In the second dimension, an ADME column was applied for further separation. After optimization of the separation conditions, a six-way valve was utilized for direct transformation of the target fraction from the 1st column to the 2nd column. A dynamic range of 2.5 ng/mL to 500 ng/mL was achieved with correlation coefficient (r ²) greater than 0.9995. The limit of detection and limit of quantification were determined to be 0.69 and 2.30 ng/mL, respectively. The 2D-LC method shows high sensitivity, good reproducibility, and recovery for methomyl in tobacco samples. Therefore, the new method was quite suitable for routine analysis.

Progress in the pretreatment and analysis of N-nitrosamines: an update since 2010

As highly toxic substances, N-nitrosamines (NAs) have been proved to cause carcinogenesis and mutagenesis in humans. Therefore, to carefully monitor safety and preserve human health, the development of rapid, accurate, and high-sensitivity determination methods of NAs is of substantial importance. This review provides a current-status comprehensive summary of the pretreatment and determination methods of NAs in various samples since 2010. Common pretreatment methods that have been used to extract and purify targets include solid-phase extraction, liquid-liquid extraction and various microextraction methods, such as solid-phase microextraction and liquid-phase microextraction, among others. Determination methods include liquid chromatography, gas chromatography, supercritical fluid chromatography and electrochemical methods, among others. In addition, we discuss and compare the advantages and disadvantages of various pretreatment and analytical methods and examine the prospects in this area.

Use of autoclave extraction-supercritical fluid chromatography/tandem mass spectrometry to analyze 4-(methylintrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosonornicotine in tobacco

4-(methylintrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are the most prevalent and toxic tobacco specific nitrosamines (TSNAs). Due to their carcinogenicity, knowledge of the composition of NNK and NNN in tobacco is necessary. Herein, a sensitive and rapid method, which employs autoclave extraction-supercritical fluid chromatography/tandem mass spectrometry (SFC-MS/MS), has been developed for the analysis of NNK and NNN in tobacco. Both water-soluble and matrix-bound NNK and NNN were extracted with 100 mM ammonium acetate in an autoclave (130 °C, 4 h), and the aqueous extract was subjected to solvent replacement prior to SFC-MS/MS analysis. NNK and NNN were effectively separated within 5 min by using supercritical CO2 as the main mobile phase coupled with a co-solvent of methanol. Excellent linearity was obtained with coefficients of determination (R2) greater than 0.9997 in the range of 1-160 ng/mL and 5-800 ng/mL for NNK and NNN, respectively. The recoveries were in the range of 92.5-110.0% at different spiked levels of real samples. 12 tobacco samples which include 3 typical tobacco varieties of burley, flue-cured, and oriental tobaccos had been analyzed, and the fraction of matrix-bound NNK was determined as well. In addition, a comparison between the proposed SFC-MS/MS method and a validated liquid chromatography tandem mass spectrometry (LC-MS/MS) internal standard method was conducted. Both techniques exhibit comparable analysis results, but peak splitting of NNN was observed by LC-MSMS due to the existence of E/Z isomers, while SFC-MS/MS offers great improvement through elution condition optimization, demonstrating the applicability of SFC-MS/MS as an alternative tool for NNK and NNN analysis.

Simultaneous determination of tobacco minor alkaloids and tobacco-specific nitrosamines in mainstream smoke by dispersive solid-phase extraction coupled with ultra-performance liquid chromatography/tandem orbitrap mass spectrometry

RATIONALE

The minor alkaloids in tobacco play an important role in the chemical composition of cigarette smoke, and they are precursors of tobacco-specific nitrosamines (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), N-nitrosoanabasine (NAB) and N-nitrosoanatabine (NAT)). NNN and NNK are classified as group 1 carcinogens. A method quantitating both tobacco minor alkaloids and tobacco-specific nitrosamines in mainstream smoke has not been reported.

METHODS

Tobacco minor alkaloids and tobacco-specific nitrosamines in cigarette mainstream smoke were extracted by sonication. The extract was cleaned up by dispersive solid-phase extraction, and separation was achieved via ultra-performance liquid chromatography/tandem orbitrap mass spectrometry.

RESULTS

The method was validated by analysis of six replicate samples spiked with three levels of the analyses. The mean recoveries for the six replicates were from 84.7% to 118% with less than 15% relative standard deviation except myosmine at the low spiked level and the calculated detection limits were 0.066 to 13.2 ng/cig, respectively. The mean concentrations of nicotyrine, anabasine, nornicotine, anatabine, myosmine, 2,3-bipyridine, cotinine, nicotelline, N-formylnornicotine, NNK, NNN, NAB and NAT in 30 different brands of commercial cigarette smoke under the ISO smoking regimen were 2.50 μg/cig, 2.34 μg/cig, 3.21 μg/cig, 5.78 μg/cig, 2.83 μg/cig, 1.05 μg/cig, 1.55 μg/cig, 0.55 μg/cig, 2.48 μg/cig, 6.06 ng/cig, 3.62 ng/cig, 0.40 ng/cig and 6.15 ng/cig, respectively.

CONCLUSIONS

The proposed method was suitable for analysis of tobacco minor alkaloids and tobacco-specific nitrosamines in cigarette mainstream smoke.