Simultaneous determination of eugenol, isoeugenol and methyleugenol in fish fillet using gas chromatography coupled to tandem mass spectrometry

Development of broad-spectrum immunoassay with monoclonal antibody to detect five eugenols and study of their molecular recognition mechanism

In this study, three eugenol fragment-containing haptens were synthesized, and a monoclonal antibody (mAb) selective for five commonly-found eugenol compounds (EUGs, i.e., eugenol, isoeugenol, methyl eugenol, methyl isoeugenol, and acetyl isoeugenol) was obtained. Based on this mAb, a broad-spectrum indirect competitive ELISA for high-throughput detection of five EUGs was developed. The detection limits for eugenol, isoeugenol, methyl eugenol, methyl isoeugenol and acetyl isoeugenol in both tilapia and shrimp samples were 25.3/ 50.6 μg/kg, 0.075/0.15 μg/kg, 0.48/0.96 μg/kg, 0.16/0.32 μg/kg, and 18.16/36.32 μg/kg, respectively. The recoveries for five EUGs ranged from 80.4 to 114.0 % with a coefficient of variation less than 11.5 %. Moreover, homology modelling and molecular docking were conducted to elucidate the interactions mechanism of mAb-EUGs. The work provides a promising tool for high-throughput screening of EUGs in aquatic products, which can serve as a benchmark for designing haptens and developing immunoassays for other small molecules.

Gold nanocluster-based ratiometric fluorescence immunoassay for broad-spectrum screening of five eugenols

BACKGROUND

Eugenol compounds (EUGs), which share chemical similarities with eugenol, belong to a group of phenolic compounds primarily found in clove oil. They are highly valued by fish dealers due to their exceptional anesthetic properties, playing a crucial role in reducing disease incidence and mortality during the transportation of live fish. Despite their widespread use, the safety of EUGs remains a contentious topic, raising concerns about the safety of aquatic products. This underscores the need for efficient and sensitive analytical methods for detecting EUGs.

RESULTS

Nanomaterial-based ratiometric fluorescence immunoassay has gained increasing attention due to its integration of the immunoassay's excellent specificity and compatibility for high-throughput analysis, coupled with the exceptional sensitivity and anti-interference capabilities of ratiometric fluorescence assays. In this study, we developed a sensitive ratiometric fluorescence immunoassay for screening five EUGs. This method employs a broad-specificity monoclonal antibody (mAb) as a recognition reagent, selective for five EUGs. It leverages the horseradish peroxidase (HRP)-triggered formation of fluorescent 2,3-diaminophenazine (DAP) and the quenching of fluorescent gold clusters (Au NCs) for detection. The assay's detection limits for eugenol, isoeugenol, eugenol methyl eugenol, methyl isoeugenol, and acetyl isoeugenol in tilapia fish and shrimp were found to be 9.8/19.5 μg/kg, 0.11/0.22 μg/kg, 19/36 Tilapia ng/kg, 8/16 ng/kg, and 3.0/6.1 μg/kg, respectively. Furthermore, when testing spiked Tilapia fish and shrimp samples, recoveries ranging from 84.1 to 111.9 %, with the coefficients of variation staying below 7.1 % was achieved.

SIGNIFICANCE

This work introduces an easy-to-use, broad-specificity, and highly sensitive method for the screening of five EUGs at a pg/mL level, which not only provides a high-throughput strategy for screening eugenol-type fish anesthetics in aquatic products, but also can serve as a benchmark for developing immunoassays for other small molecular pollutants, rendering potent technological support for guarding food safety and human health.

Analysis and Stability Study of Isoeugenol in Aquaculture Products by Headspace Solid-Phase Microextraction Coupled to Gas Chromatography-Mass Spectrometry

Headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) offers an alternative analysis method for isoeugenol (an active ingredient in fish sedatives) that avoids the use of organic solvents, simplifies sample preparation, and can be fully automated. This work focuses on developing and evaluating an HS-SPME-GC-MS method for isoeugenol in aquaculture samples and testing the stability of isoeugenol itself. Because of isoeugenol's relatively low volatility, more polar SPME fiber coatings (polyacrylate and polydimethylsiloxane/divinylbenzene) had better performance and the headspace extractions took over 30 min to reach equilibrium. Additionally, it was found that isoeugenol was relatively unstable compared to a deuterated standard (d3-eugenol) in the presence of water. To address this, after the fish samples were homogenized with water, they were heated at 50 °C for 1 h prior to analysis for equilibration. By using the method developed in this work, isoeugenol's detection limits in multiple aquaculture matrices (shrimp, tilapia, and salmon) were in the low ng/g range (<15 ng/g), well below the target testing level (200 ng/g). Additionally, by adding d3-eugenol as an internal standard, excellent linearity (R2 > 0.98), accuracy (97-99% recoveries), and precision (5-13% RSDs) were all achieved.

Quantitative NMR Spectrometry of Phenylpropanoids, including Isoeugenol in Herbs, Spices, and Essential Oils

Isoeugenol (2-methoxy-4-(1-propenyl)phenol) has been recently classified as possibly carcinogenic to humans (Group 2B) by the International Agency for Research on Cancer (IARC). This study conducted an analysis of isoeugenol in common herbs and spices, including basil, cinnamon, ginger, and nutmeg, using 1H nuclear magnetic resonance (NMR) spectrometry. Additionally, over 1300 coffee samples were analysed by 1H-NMR for isoeugenol, but it was not detected in any of the analysed samples. Various essential oils, including nutmeg, basil, clove, sweet flag, and ylang-ylang oils, were examined for isoeugenol content. Out of the twelve nutmeg oils tested, four contained isoeugenol, with concentrations ranging from 3.68 ± 0.09 g/kg to 11.2 ± 0.10 g/kg. However, isoeugenol was not detected in the essential oils of calamus, basil, ylang-ylang, and clove using NMR spectrometry. These findings warrant critical evaluation of the previous literature, given reports of high isoeugenol levels in some of these matrices. A toxicological assessment has determined that there is no risk to human health by exposure to isoeugenol via nutmeg essential oils.

Determination of Eugenol Residues in Fish Tissue, Transport, and Temporary Water of Aquatic Product by Gas Chromatography-Tandem Mass Spectrometry with Application of the Electrospun Nanofibrous Membrane

Using gas chromatography-tandem mass spectrometry and electrospun nanofibrous membrane, we developed and validated a simple, rapid, and sensitive methodology for quantifying eugenol residues in fish tissue and water samples. Fish tissue extract and water samples (315 samples) collected from three southeastern China provinces (Shanghai, Zhejiang, and Fujian), originating from eight provinces of Zhejiang, Jiangsu, Shandong, Guangdong, Fujian, Anhui, Shanghai, and Jiangxi, from April 2021 to April 2023 were filtered with an electrospun nanofiber membrane, extracted with trichloromethane/n-hexane, and directly concentrated to dry after simple purification. An internal standard of p-terphenyl in n-hexane and 5-µL injection volumes of the solutions was used to analyze eugenol via internal calibration with a minimum concentration of 0.5 µg/L in water samples and 0.1 µg/kg in aquatic product samples. The highest amount of eugenol was detected in Fujian province, possibly due to the higher temperature during transportation, while the lowest amount was found in Shanghai, which mainly uses temporary fish-culture devices. This is a fast, inexpensive, and effective method for testing large quantities of fish water and meat samples.

Urinary Excretion of Mercapturic Acids of the Rodent Carcinogen Methyleugenol after a Single Meal of Basil Pesto: A Controlled Exposure Study in Humans

Methyleugenol (ME), found in numerous plants and spices, is a rodent carcinogen and is classified as "possibly carcinogenic to humans". The hypothesis of a carcinogenic risk for humans is supported by the observation of ME-derived DNA adducts in almost all human liver and lung samples examined. Therefore, a risk assessment of ME is needed. Unfortunately, biomarkers of exposure for epidemiological studies are not yet available. We hereby present the first detection of N-acetyl-l-cysteine conjugates (mercapturic acids) of ME in human urine samples after consumption of a popular ME-containing meal, pasta with basil pesto. We synthesized mercapturic acid conjugates of ME, identified the major product as N-acetyl-S-[3'-(3,4-dimethoxyphenyl)allyl]-l-cysteine (E-3'-MEMA), and developed methods for its extraction and LC-MS/MS quantification in human urine. For conducting an exposure study in humans, a basil cultivar with a suitable ME content was grown for the preparation of basil pesto. A defined meal containing 100 g of basil pesto, corresponding to 1.7 mg ME, was served to 12 participants, who collected the complete urine at defined time intervals for 48 h. Using d6-E-3'-MEMA as an internal standard for LC-MS/MS quantification, we were able to detect E-3'-MEMA in urine samples of all participants collected after the ME-containing meal. Excretion was maximal between 2 and 6 h after the meal and was completed within about 12 h (concentrations below the limit of detection). Excreted amounts were only between 1 and 85 ppm of the ME intake, indicating that the ultimate genotoxicant, 1'-sulfooxy-ME, is formed to a subordinate extent or is not efficiently detoxified by glutathione conjugation and subsequent conversion to mercapturic acids. Both explanations may apply cumulatively, with the ubiquitous detection of ME DNA adducts in human lung and liver specimens arguing against an extremely low formation of 1'-sulfooxy-ME. Taken together, we hereby present the first noninvasive human biomarker reflecting an internal exposure toward reactive ME species.

Fluorescent microsphere-based lateral-flow immunoassay for rapid and sensitive determination of eugenols

In this study, a sensitive monoclonal antibody (mAb) 1B5 against eugenols was prepared based on a novel hapten. Based on this mAb, a paper-based lateral-flow immunoassay (LFIA) was developed using Eu-fluorescent microspheres sensor, that could achieve qualitative and quantitative detection of eugenols within 10 min. Results showed colorimetric values observed by the naked eye were 12.3 µg/kg, 12.3 µg/kg, 37 µg/kg and 111 µg/kg for eugenol, isoeugenol, methyl eugenol, and methyl isoeugenol, respectively, in both water and fish samples. For quantitative detection of eugenol, isoeugenol, methyl eugenol and methyl isoeugenol, the detection ranges were 4.49-48.4 µg/kg, 6.02-66.8 µg/kg, 16.5-150 µg/kg and 47.9-710 µg/kg in water, and 3.9-30.9 µg/kg, 5.9-62.6 µg/kg, 16.7-255 µg/kg, and 44.5-890 µg/kg in fish, respectively. The recovery test and detection in fish demonstrated the reliability of the LFIA in real samples. Therefore, the developed LFIA produced a promising alternative tool for the rapid on-site detection of eugenols.

Simultaneous determination of the residues of anesthetics and sedatives in fish using LC-QLIT-MS/MS combined with DSPE

Liquid chromatography coupled with quadrupole linear ion trap tandem mass spectrometry (LC-QLIT-MS/MS) technology operated in electrospray ionization (ESI) was developed for tracing anesthetic (AETs) and sedatives (SDTs) in fish. Sampling procedure was achieved by using acetonitrile extraction followed by dispersive solid phase extraction (DSPE) clean-up. Under the optimized laboratory conditions, reliable qualitative confirmation was obtained through the multiple reaction monitoring-information dependent acquisition-enhanced product ion (MRM-IDA-EPI) mode. Results indicated a favorable linear in the concentration range of 1-100 μg∙kg^-1 (0.1-10 μg∙kg^-1 for MS-222), with regression coefficient not less than 0.9997. The detection limit ranges from 0.03 to 0.4 μg∙kg^-1 (S/N = 3). The validated method was applied to determine AETs and SDTs in fish with satidfied recoveries of 86.3 %-111.7 % and the relative standard deviations (RSD) of 1.9 %-8.9 % (n = 6). Practical samples analysis indicated that the proposed method is simple, rapid, sensitive and accurate for identification of AETs and SDTs.

A Non-aqueous Capillary Electrophoresis for Determination of Eugenol in Cloves and Dental Preparations

A total non-aqueous capillary electrophoresis method was developed and applied for the first time for the quantification of eugenol in cloves and dental preparations. The optimized conditions included a buffer consisting of 150 mM sodium acetate and 300 μL 1 M acetic acid methanol solution (30 mM), an applied voltage of 25 kV, and a temperature of 25 °C and an applied wavelength of 214 nm. The developed method of determining the eugenol was characterized by the following parameters: a detection time within 1.97 min, good linearity (R2 = 0.9989–0.9999), detection limit at the level from 0.19 to 0.35 µg mL−1, very good extraction yield of 99.6–100.6% from both methanol standard solutions, clove buds’ matrix, and dental preparations. Limit of quantitation at the level from 0.81 to 0.98 µg mL−1. The method is based on the developed one-step extraction procedure. Moreover, the developed method does not require the use of any eugenol solubility enhancers such as SDS.

Hydrophobic deep eutectic solvent-based ultrasonic-assisted liquid-liquid microextraction combined with GC for eugenol, isoeugenol, and methyl isoeugenol determination in aquatic products

The use of deep eutectic solvents (DESs) has great prospects because of the green and efficient characteristics, which can be used for developing analytical methods for foods. In this research, assisted by ultrasonic waves, a liquid-liquid microextraction detection method combined with gas chromatography was established for three anaesthetics (eugenol, isoeugenol, and methyl isoeugenol) in aquatic food. The processing conditions including the components, ratio of hydrogen bond acceptor and hydrogen bond donor, DES volume, ultrasonic time, and pH were evaluated and optimised to improve the extraction efficiency, which was based on the DES structures and properties. In-house method validation was carried out by applying to real samples. A Thymol: levulinic acid DES (with a molar ratio of 1:2) was used as the extractant and the recoveries were as high as 93-101% for eugenol, 90-100% for methyl isoeugenol, and 86-94% for isoeugenol with RSDs <5% under optimum conditions. The limit of detection and quantification of the eugenol compounds were 0.08-0.10 μg/mL and 0.26-0.33 μg/mL, respectively. The method has green credentials and comparable LOD to homologous apparatus, which can be used for the determination of eugenol components in aquatic food.

[Study of the stability of 2-methoxy-4-(2-propenyl) hydroxybenzene in biological material]

The purpose of this work is to study the stability of 2-methoxy-4-(2-propenyl)hydroxybenzene [2-MO-4-(2-P)HOB] in biological material. For analysis, gas chromatography-mass spectrometry (GC-MS) was used: column DB-5MS EVIDEX (25 m × 0.2 mm) with a stationary phase of 5%-phenyl-95%-dimethylpolysiloxane; thin layer chromatography (TLC): Sorbfil plates, hexane-dioxane-propanol-2 mobile phase (40:5:1) and UV spectrophotometry (solvent - 95% ethanol). 2-MO-4-(2-P)HOB was isolated from the biomatrix (liver tissue) by infusion with a mixture of ethyl acetate-acetone (7:3). Purification of the analyte was carried out by combining extraction (water-ethyl acetate system) and semi-preparative column chromatography [sorbent - silica gel L 40/100 μm, eluent - hexane-dioxane (8.5:1.5)]. It was established that at -22 °C, 4 °C, 12 °C, 20 °C and 30 °C 2-MO-4-(2-P)HOB is stored in the liver tissue for 385, 357, 301, 245 and 217 days, respectively. We studied the possibility of mathematical description of the dynamics of analyte decomposition in a biomaterial (liver tissue) at the indicated temperatures using the hyperbolic equation. The coefficients in the hyperbola equation (k_av), calculated according to the results of the experiment, for temperatures of -22 °C, 4 °C, 12 °C, 20 °C and 30 °C amounted to 6223, 3036, 2387, 1903 and 932, respectively., which is described by the equation: kav=101.19∙(50-to)-1272.78. It was established that on the basis of this equation it is possible to predict the nature of the stability of 2-MO-4-(2-P)HOB in the biomaterial (liver tissue) at temperatures in the range from -22 °C to 30 °C.

[Features of assay and decomposition dynamics of 2-methoxy-4-(1-propenyl)hydroxybenzene in biological material]

The objective was to study the features of assay and dynamics of decomposition of 2-methoxy-4-(1-propenyl)hydroxybenzene in biological material. Extraction, semi-preparation chromatography, TLC, HPLC, GC-MS and UV-spectrophotometry were used as test methods. 2-Methoxy-4-(1-propenyl)hydroxybenzene was extracted from the biological material by double infusion (45 min each) with ethyl acetate at a 2:1 mass ratio of isolating agent and biomatrix. Purification was performed by extraction and chromatography in a semi-preparative (190×10 mm) L 40/100 μm silica gel column using a hexane-dioxane (7:3) eluent. The analyte was determined by TLC methods (Sorbfil plates, hexane-acetone 9:1 as a mobile phase), HPLC [Discovery C18 HPLC Column (250×4.6 mm), acetonitrile-acetate buffer pH 5.5 (5:5) as a mobile phase], GC-MS [DB-5MS EVIDEX (25 m×0.2 mm) column with 5%-phenyl-95% dimethyl polysiloxane as a stationary phase], UV-spectrophotometry (95% ethanol as a solvent). The proposed assay method for 2-methoxy-4-(1-propenyl)hydroxybenzene in biomaterial (liver tissue) is validated for linearity, selectivity, accuracy and precision. The study results showed that the decomposition rate of the analyte increases as the store temperature increases. At 0-2 °C, 8-10 °C and 18-22 °C 2-methoxy-4-(1-propenyl)hydroxybenzene is stable for 480, 390 and 260 days respectively.

SAFE and SBSE combined with GC-MS and GC-O for characterization of flavor compounds in Zhizhonghe Wujiapi medicinal liquor

Volatile compounds in Chinese Zhizhonghe Wujiapi (WJP) medicinal liquor were extracted by solvent-assisted flavor evaporation extraction (SAFE) and stir bar sorptive extraction (SBSE), respectively, and identified by gas chromatography-mass spectrometry. Results showed that a total of 123 volatile compounds (i.e., 108 by SAFE, 50 by SBSE, and 34 by both) including esters, alcohols, acids, aldehydes, ketones, heterocycles, terpenes and terpenoids, alkenes, phenols, and other compounds were identified, and 67 of them were confirmed as aroma-active compounds by the application of the aroma extract dilution analysis coupled with gas chromatography-olfactometry. After making a simulated reconstitute by mixing 41 characterized aroma-active compounds (odor activity values ≥1) based on their concentrations, the aroma profile of the reconstitute showed good similarity to that of the original WJP liquor. Omission test further corroborated 34 key aroma-active compounds in the WJP liquor. The study of WJP liquor is expected to provide some insights into the characterization of special volatile components in traditional Chinese medicine liquors for the purpose of quality improvement and aroma optimization.

Dispersive solid-phase extraction combined with high-performance liquid chromatography for determination of seven anesthetics in aquatic products

随着麻醉剂广泛用于渔业生产过程和水产品运输等领域,建立水产品中麻醉剂残留的检测方法具有重要意义。由于水产品基质复杂且麻醉剂残留水平低,因此需要合适的前处理方法以提高检测灵敏度。该研究基于分散固相萃取-高效液相色谱,建立了一种同时检测水产品中普鲁卡因、丁氧卡因、三卡因、丁香酚、甲基丁香酚、异丁香酚、甲基异丁香酚7种麻醉剂的分析方法。前处理采用分散固相萃取;确定了1.0%甲酸乙腈为提取溶剂,20 mg苯乙烯-甲基丙烯酸缩水甘油酯聚合物微球(PS-GMA)、50 mg N-丙基乙二胺(PSA)和10 mg C18混合吸附剂为净化剂,二甲基亚砜(DMSO)辅助氮吹的前处理方法;优化了提取时间和DMSO用量等条件。7种麻醉剂采用Welch welchrom C18色谱柱(250 mm×4.6 mm, 5 μm)进行分离,以甲醇和0.05%甲酸-5 mmol/L乙酸铵水溶液为流动相进行梯度洗脱,检测波长为235、260和290 nm,以鱼肉和对虾两种基质匹配标准曲线进行定量分析。实验结果表明,在优化的实验条件下,7种目标麻醉剂在各自的浓度范围内具有良好的线性关系(相关系数R²>0.999),检出限(LOD)为0.011~0.043 mg/kg。在鱼肉样品中,3个水平的平均加标回收率为79.7%~109%,相对标准偏差(RSD)低于7.2%;在对虾样品中,平均回收率为78.0%~99.9%, RSD低于8.3%。该方法具有快捷简便、操作简单、灵敏度高等优点,可应用于水产品中3种氨基苯甲酸酯类和4种丁香酚类麻醉剂的检测。

[Solid phase microextraction-high performance liquid chromatography of fluorinated covalent organic polymer to determine eugenol anesthetics in aquatic products]

Fluorinated covalent organic polymers (F-COPs) constitute a new class of porous materials with a topological structure, large surface area, and potential superiority over other types of polymers in sample preparation. In this study, a F-COP was rapidly synthesized by a simple Schiff-based reaction using 2,3,5,6-tetrafluoroterephthalaldehyde (TFA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as monomers, and by adding scandium (Ⅲ) triflate (Sc(OTf)₃) as the metal catalyst at room temperature. The prepared F-COP was applied as a coating adsorbent for solid phase microextraction (SPME) to enrich three kinds of eugenol anesthetics in aquatic products. The extraction performance of an enrichment medium is an important factor for practical application in real analytical projects. This F-COP adsorbent with rich π-stacking electrons contained abundant phenyl rings and imine (-C=N) groups throughout the molecular framework. The adsorption mechanism was explored and discussed based on the π-π affinity and hydrogen bonding interaction, which contributed to its strong recognition affinity to targets. The F-COP was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, and scanning electron microscopy (SEM). The results indicated that the novel F-COP-SPME bar exhibited a rough and porous surface structure, good preparation reproducibility, and high stability. High performance liquid chromatography (HPLC) was performed with an ultraviolet-visible (UV-vis) wavelength detector. A Diamonsil plus C18 column (250 mm×4.6 mm, 5 μm) was used as the analytical column. The mobile phase comprised 60% methanol and 40% ultrapure water, and was flowed at 0.800 mL/min. The injected volume of the sample was 20.0 μL. The column temperature was maintained at 30 ℃ and the detection wavelength was set to 280 nm. Further, the SPME conditions (including extraction time, stirring rate, desorption solvent, and desorption time) that influenced the extraction efficiencies of the eugenol anesthetics were investigated in detail. Thus, the optimized F-COP-SPME bar conditions were established as follows: extraction time: 30 min; stirring rate: 700 r/min; desorption solvent: acetonitrile; desorption time: 10 min. By combining F-COP-based SPME with HPLC-UV analysis, an effective method was developed for the extraction and determination of eugenol, eugenyl acetate, and methyl eugenol residues in aquatic products. The method demonstrated good linearity in the range of 10-1000 μg/L for eugenol and eugenyl acetate, and 10-1500 μg/L for methyl eugenol, with correlation coefficients (r²) greater than 0.9961, low limits of detection (2.9-4.5 μg/kg, S/N=3), and excellent precision (relative standard deviations lower than 8.7%, n=5). Finally, the method was applied for the effective extraction of three kinds of eugenol anesthetics from tilapia and shrimp samples. The obtained recoveries were in the range of 76.7%-98.7% and 80.3%-104% with relative standard deviations of 8.5%-11.8% and 8.6%-12.4% (n=5), respectively. These results demonstrated that the F-COP is promising for use as an adsorbent in SPME for the determination of eugenol anesthetics in aquatic products. The developed method was suitable for the qualitative and quantitative determination of three kinds of eugenol anesthetics in aquatic products, yielding a satisfactory purification effect and sensitivity.

Determination of Six Eugenol Residues in Aquatic Products by Gas Chromatography-Orbitrap Mass Spectrometry

Eugenol compounds are widely used in the circulation and transportation of fresh aquatic products because of their good anesthetic effects. However, some studies have shown that eugenol compounds are potential carcinogens. Therefore, in order to ensure the edible safety of aquatic products, eugenol compounds in aquatic products need to be screened quickly. A method for determination of six eugenol residues in aquatic products was established by multiplug filtration cleanup (m-PFC), combined with gas chromatography-Orbitrap mass spectrometry (Orbitrap GC-MS). Samples were ultrasonically extracted with acetonitrile, and the extracts were frozen at −18°C for 1 h, then purified with the m-PFC column, and detected by Orbitrap GC-MS in full scan mode. The results showed the linear relationships for six eugenols were good in the range of 0.001–0.1 μg/mL, and the correlation coefficients (R2) were above 0.9950. The limits of detection (LODs) were 2–10 μg/kg, and the limits of quantitation (LOQs) were 5–20 μg/kg. The average recoveries at the spiked levels of 5–200 μg/kg were in the range of 76.4%–105.1%, with relative standard deviations (RSDs) of 1.2%–7.5%. Eighty aquatic products were detected by this method, of which only eugenol was detected in 12 samples, and eugenol and isoeugenol were detected in two samples at the same time. The other eugenol compounds were not detected in any sample. The detection rate of positive samples was 17.5%. The method is simple, accurate, and suitable for the rapid screening of eugenol compounds in aquatic products.

Analytical Separation of Carcinogenic and Genotoxic Alkenylbenzenes in Foods and Related Products (2010-2020)

Alkenylbenzenes are potentially toxic (genotoxic and carcinogenic) compounds present in plants such as basil, tarragon, anise star and lemongrass. These plants are found in various edible consumer products, e.g., popularly used to flavour food. Thus, there are concerns about the possible health consequences upon increased exposure to alkenylbenzenes especially due to food intake. It is therefore important to constantly monitor the amounts of alkenylbenzenes in our food chain. A major challenge in the determination of alkenylbenzenes in foods is the complexity of the sample matrices and the typically low amounts of alkenylbenzenes present. This review will therefore discuss the background and importance of analytical separation methods from papers reported from 2010 to 2020 for the determination of alkenylbenzenes in foods and related products. The separation techniques commonly used were gas and liquid chromatography (LC). The sample preparation techniques used in conjunction with the separation techniques were various variants of extraction (solvent extraction, liquid-liquid extraction, liquid-phase microextraction, solid phase extraction) and distillation (steam and hydro-). Detection was by flame ionisation and mass spectrometry (MS) in gas chromatography (GC) while in liquid chromatography was mainly by spectrophotometry.

Development and evaluation of a novelty single-step cleanup followed by HPLC-QTRAP-MS/MS for rapid analysis of tricaine, tetracaine, and bupivacaine in fish samples

A novelty single-step cleanup method combined with HPLC coupled with triple quadrupole-linear ion trap MS/MS (HPLC-QTRAP-MS/MS) was developed for the analysis of tricaine, tetracaine, and bupivacaine in fish tissue. The target analytes were extracted using acetonitrile based on the modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method under ultrasound irradiation. A cheap analytical filtration syringe (CAFS) cleanup column for single-step purification was proposed first; 300 mg of primary/secondary amino was proposed as the optimum purification sorbent; 1 mL of acetonitrile extract was transferred into a CAFS cleanup column and purified for analysis using HPLC-QTRAP-MS/MS. The limits of detection and the limits of quantification were 2.0 and 5.0 μg kg^-1 , respectively. The recoveries were in the range of 88.73-108.72%. Inter-day and intra-day relative standard deviations were lower than 15% for all analytes. The developed method has been applied to measure real samples obtained from the local market.

HS-SPME and SDE combined with GC-MS and GC-O for characterization of flavor compounds in Zhizhonghe Wujiapi medicinal liquor

Volatile compounds in Chinese medicinal liquor, Zhizhonghe Wujiapi (WJP liquor), were extracted by headspace-solid-phase microextraction (HS-SPME) and simultaneous distillation and extraction (SDE), respectively, and identified and quantified by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). Results showed that a total of 133 volatile compounds (i.e., 99 by HS-SPME, 67 by SDE, and 33 by both) including esters, alcohols, acids, aldehydes, ketones, furans, terpenes, and other miscellaneous compounds were identified by GC-MS. A total of 66 aroma active compounds were further recognized by GC-O, and 43 of them were confirmed as key aroma compounds owing to their high OAV values. After making a simulated reconstitute by mixing 31 characterized aroma compounds (OAVs ≥ 1) based on their measured concentrations, the aroma profile of the reconstitute showed a good similarity to the aroma of the original WJP liquor. Omission test further corroborated 25 key aroma-active compounds in the WJP liquor. The analysis of the volatile components of this special Chinese medicinal liquor is expected to provide some insights in terms of its quality improvement and aroma profile optimization.

Chiral determination of nornicotine, anatabine and anabasine in tobacco by achiral gas chromatography with (1S)-(-)-camphanic chloride derivatization: Application to enantiomeric profiling of cultivars and curing processes

The alkaloid enantiomers are well-known to have different physiological and pharmacological effects, and to play an important role in enantioselectivity metabolism with enzymes catalysis in tobacco plants. Here, we developed an improved method for simultaneous and high-precision determination of the individual enantiomers of nornicotine, anatabine and anabasine in four tobacco matrices, based on an achiral gas chromatography-nitrogen phosphorus detector (GCNPD) with commonly available Rtx-200 column using (1S)-(-)-camphanic chloride derivatization. The method development consists of the optimization of extraction and derivatization, screening of achiral column, analysis of the fragmentation mechanisms and evaluation of matrix effect (ME). Under the optimized experimental conditions, the current method exhibited excellent detection capability for the alkaloid enantiomers, with coefficients of determination (R2) > 0.9989 and normality test of residuals P > 0.05 in linear regression parameters. The ME can be neglected for the camphanic derivatives. The limit of detection (LOD) and limit of quantitation (LOQ) ranged from 0.087 to 0.24 μg g - 1 and 0.29 to 0.81 μg g - 1, respectively. The recoveries and within-laboratory relative standard deviations (RSDR) were 94.3%~104.2% and 0.51%~3.89%, respectively. The developed method was successfully applied to determine the enantiomeric profiling of cultivars and curing processes. Tobacco cultivars had a significant impact on the nornicotine, anatabine, anabasine concentration and enantiomeric fraction (EF) of (R)-nornicotine, whereas the only significant change induced by the curing processes was an increase in the EF of (R)-anabasine.

Elimination kinetics of eugenol in grass carp in a simulated transportation setting

BACKGROUND

Fish are vulnerable to stress from over-crowding during transportation and eugenol is the most common sedative used to minimize fish injury. The ADI value of 2.5 mg/kg is recommended by the Joint FAO/WHO Expert Committee on Food Additives. The aim of this work was to study the elimination kinetics of eugenol following exposure of grass carp to a eugenol bath in a simulated transportation setting.

RESULTS

Grass carp, Ctenopharyngodon idella (120 fish) were exposed for 24 h to a 10 mg/L eugenol bath. Sampling was performed during a 96 h period after the 24 h bath. Eight fish were sampled at each time point and muscle, plasma and liver concentrations of the drug were determined by ultra-performance liquid chromatography-tandem mass spectrometry. The concentration-time data of eugenol in each tissue were analyzed using non-compartmental methods. The peak concentrations (C_max) in plasma, muscle and liver were 7.68, 5.30 and 24.63 mg/kg and the elimination half-lives (t_1/2β) were 19.79, 10.27 and 55.28 h, respectively. The clearance (CL) values were 0.10, 0.44 and 0.04 L/h/kg and the areas under the concentration-time curve (AUC_0-96h) were 91.54, 22.44, and 214.12 mg·h/L in plasma, muscle and liver, respectively. After a eugenol exposure bath, drug concentrations in muscle tissue of grass carp were below 1 mg/kg at 8 h and 0.1 mg/kg at 24 h.

CONCLUSIONS

The drug concentrations in muscle tissue at 8 h were lower than the recommended ADI value.