Determination of 4(5)-methylimidazole in foods and beverages by modified QuEChERS extraction and liquid chromatography-tandem mass spectrometry analysis

Research progress on generation, detection and inhibition of multiple hazards - acrylamide, 5-hydroxymethylfurfural, advanced glycation end products, methylimidazole - in baked goods

While baking produces attractive flavors for foods, it also generates various endogenous by-products, including acrylamide (AA), 5-hydroxymethylfurfural (5-HMF), advanced glycation end products (AGEs) and methylimidazole (MI). This review briefly presents the recent studies on the above hazards, and research progress on the formation and control of the above substances in detail. There have been more detailed studies on a single category of hazards. However, few studies and reports have considered the integrated prevention and control of multiple hazards, which is related to the difficulty of analyzing the reaction mechanisms of multiple hazards at multiple scales and under multiple phases in complex food matrices. In this regard, the sample pretreatment methods are a crucial step in achieving simultaneous detection. The coordinated implementation of various methods, including reducing precursor levels, modifying baking conditions and equipment, and incorporating exogenous additives, is necessary to achieve a synchronized reduction in multiple hazardous substances.

The Application of Cold-Induced Liquid-Liquid Extraction for the Determination of 4-Methylimidazole in Tea and Associated Risk Assessment for Chinese Tea Consumers

4-Methylimidazole (4-MEI), as a Maillard reaction product, often occurs in heat-processed food. Due to its widespread occurrence and strong carcinogenicity in food and beverages, 4-MEI has received attention from regulatory organizations and consumers. Some studies have reported the occurrence and exposure of 4-MEI in food, but few studies have involved traditional tea beverages, which is related to the limited analytical methods currently being influenced by complex tea matrices. For this issue, this study presents a simple, reliable, and highly sensitive analytical method for the determination of 4-MEI in tea using liquid chromatography-high resolution mass spectrometry. By means of this method, a total of 570 tea samples from typical tea-producing regions in China were monitored for contamination of 4-MEI. The results showed that the average 4-MEI level (136 μg/kg) in oolong tea was significantly higher than that in other types of tea samples. Based on contamination levels and tea consumption data in China, the daily intake doses (0.04-1.16 μg/day) of 4-MEI among tea consumers were obtained. As a result, the health risk of Chinese tea consumers consuming 4-MEI alone through tea consumption is relatively low, but the overall intake level of 4-MEI in other foods cannot be ignored.

4-Methylimidazole, a carcinogenic component in food, amount, methods used for measurement; a systematic review

4-methylimidazole (4-MEI) is widely used industrially. This carcinogenic component has been reported in some types of food. It is usually produced by the caramelization process in food, drinks and caramel coloring. The possible mechanism for the formation of this compound in food is the Maillard reaction. In order to estimate the amount of substance 4-MEI in food, a systematic study was conducted. The selected keywords were 4-methylimidazole, 4-MEI, beverage, drink, meat, milk, and coffee. 144 articles were obtained from the initial search. The articles were evaluated and finally, the data of 15 manuscripts were extracted. Based on the data extracted from selected articles, the highest amount is reported in caramel color, coffee, and cola drinks. In 70% of the selected studies, the analytical method was based on liquid chromatography. In this method, there is no need for derivatization. SPE columns were used to extract samples in most manuscripts. According to per capita consumption, the most exposure to 4-MEI is through coffee. In high risk food products, regular monitoring with analytical methods with high sensitivity is recommended. Furthermore, most of the selected studies were about the validation method, so few samples were selected. It is recommended to design more studies with a high sample size to accurately evaluate this carcinogenic compound in food.

Risk Assessment of Triflumezopyrim and Imidacloprid in Rice through an Evaluation of Residual Data

Triflumezopyrim, a novel mesoionic insecticide used to control planthoppers, is a potential substitute for imidacloprid. In this study, triflumezopyrim and imidacloprid residues in rice were determined using a quick, easy, cheap, effective, rugged, and safe procedure combined with ultra-high-performance liquid chromatography–tandem mass spectrometry. The limit of quantification of both triflumezopyrim and imidacloprid was 0.01 mg kg⁻¹, and the average recovery values were 94–104% and 91–106%, with relative standard deviations (RSDs) of 1.1–1.4% and 2.1–3.4% (n = 5), respectively. The consumer protection level was assessed by calculating the theoretical maximum daily intake using the reported maximum residue limits of triflumezopyrim and imidacloprid. The established method was successfully applied to 200 commercial rice samples collected from four provinces in China, and their potential public health risks were assessed using triflumezopyrim and imidacloprid residues. The risk associated with triflumezopyrim and imidacloprid dietary intake was assessed by calculating the national estimated short-term intake and the acute reference dose percentage (%ARfD). The results show that the theoretical maximum daily intake (NEDI) values of triflumezopyrim and imidacloprid in different age and gender groups were 0.219–0.543 and 0.377–0.935 μg kg⁻¹ d⁻¹ bw, and the risk quotient (RQ) values were 0.188–0.467% and 0.365–0.906%, respectively. The acute reference dose (%ARfD) of triflumezopyrim and imidaclopridin ranged from 0.615 to 0.998% and from 0.481 to 0.780%, respectively.

Application of gas flow headspace liquid phase micro extraction coupled with gas chromatography-mass spectrometry for determination of 4-methylimidazole in food samples employing experimental design optimization

Background

4-Methylimidazole (4-MeI) or 4-methyl-1H-imidazole, a slightly yellowish solid with molecular formula C₄H₆N₂, is a heterocyclic compound which supposedly does not exist as a natural product and is formed when carbohydrates are heating with ammonium compounds. This compound is used in pharmaceuticals, agriculture and photography chemicals, dyes and pigments, and rubber manufacturing. In the present study, a simple and efficient sample preparation method designated gas flow headspace liquid phase microextraction (GF-HS-SDME) was employed for the extraction and preconcentration of 4-methylimidazole (4-MeI) from food and beverage samples, before its determination by gas chromatography-mass spectrometry.

Result

To investigate the optimal conditions for the extraction process in GF-HS-SDME method, factors affecting extraction, including selection of extraction solvent, vial volume, extraction solvent ratio, position of extracting solvent, drop volume, sample volume, stirring speed, temperature, extraction time, sample pH, ionic strength of the sample solution and gas flow rate were optimized by utilizing both one-variable-at-a-time method and Plackett–Burman design. The investigation of protocol was carried out by using a standard solution containing 100.0 μg L⁻¹ of 4-MeI in deionized water.

Conclusion

In this study, a simple and green analytical method based on GF-HS-SDME was proposed for the extraction and preconcentration of 4-MeI from foodstuffs, followed by GC–MS determination. The main advantage of this method is its high preconcentration factor and fastness due to the application of an inert gas stream during microextraction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13065-022-00823-z.

[Determination of seven Alternaria toxins in infant milk powder by solid phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry]

Alternaria toxin is a general term for a class of toxic metabolites produced by Alternaria, which widely exists in soil, grain, vegetables, and fruits. This mycotoxin is extremely harmful to human health. It is well known that infant milk powder containing vegetable oil is easily contaminated by Alternaria alternata. Alternaria toxins have thus become an increasingly important focus in food. Rapid and accurate detection of Alternaria toxin residues in food is of great significance for food safety. This requires pretreatment to purify the target toxins and maximize the accuracy and precision of the analysis. In this study, a rapid method based on online solid phase extraction/purification and ultra-performance liquid chromatography-tandem mass spectrometry (online SPE UPLC MS/MS) was established to detect seven Alternaria toxins (alternariol monomethyl ether, altenuene, tenuazonic acid, alternariol, tentoxin, altenusin, and altertoxin Ⅰ) in infant milk powder. First, the mass spectrometry and chromatographic conditions were optimized. A BEH-C18 column (50 mm×2.1 mm, 1.7 μm) was selected, with 0.1% formic acid aqueous solution-acetonitrile as the mobile phase. Then, the extraction conditions (extraction agent ratio and extraction method) and the solid phase extraction process (extraction column, type and volume of the eluent, and pH of the sample loading solution) were optimized. One gram of milk powder (accurate to 0.01 g) was weighed into a 50 mL tip and bottom plug centrifuge tube. Acetonitrile-water (84∶16, v/v) was set as the extraction agent for the first two cycles, and acetonitrile-methanol-water (45∶10∶45, v/v/v) was set as the third extraction agent. Horizontal shaking for 30 min was the best extraction method. The sample was centrifuged at 9500 r/min for 10 min, and the supernatant extracted many times was mixed and blown with nitrogen at 40 ℃. The sample was redissolved in first-order water (pH 5.5), purified on an HLB column, and successively activated with 6 mL methanol and 6 mL first-order water (pH 5.5). The solution was then loaded onto the column, and the SPE was adjusted to ensure that the water sample flowed through the column at the rate of 1 mL/min so that the column did not dry up during the analysis process before the end of sample loading. The column was rinsed with 12 mL of first-order water. After leaching, the negative pressure filtration was continued for approximately 5 min, followed by elution with 10 mL methanol, and the eluted solution was directly tested after passing through a 0.22 μm filter membrane, without concentration. The analytes were determined by electrospray ionization (ESI) with alternating positive and negative ions. Under the optimal analysis conditions, the linear relationships of the seven Alternaria toxins were good in the mass concentration range of 0.5-200 μg/L, with coefficients of determination (R2)>0.9903. The limits of detection and limits of quantification were 0.15-0.64 μg/kg and 0.54-2.24 μg/kg, respectively. The recoveries of the seven Alternaria toxins were 79.1%-114.3%, and the relative standard deviations were less than 8.87% at different concentrations. The method was applied to the determination and analysis of 60 samples of infant milk powder, and the results showed that no toxin was found in stage one or stage two of the milk powder. Only one sample of the stage three of milk powder was detected, which was tentoxin, and the content was 4.97 μg/kg. The developed method is accurate, rapid, simple, sensitive, repeatable, and stable. It can be used for the practical determination of seven Alternaria toxins in infant milk powder.

A Review of the Analytical Methods for the Determination of 4(5)-Methylimidazole in Food Matrices

4(5)-Methylimidazole (4(5)MEI) is a product of the Maillard reaction between sugars and amino acids, which occurs during the thermal processing of foods. This compound is also found in foods with caramel colorants additives. Due to its prevalence in foods and beverages and its potent carcinogenicity, 4(5)MEI has received federal and state regulatory agency attention. The aim of this review is to present the extraction procedures of 4(5)MEI from food matrices and the analytical methods for its determination. Liquid and gas chromatography coupled with mass spectrometry are the techniques most commonly employed to detect 4(5)MEI in food matrices. However, the analysis of 4(5)MEI is challenging due to the high polarity, water solubility, and the absence of chromophores. To overcome this, specialized sample pretreatment and extraction methods have been developed, such as solid-phase extraction and derivatization procedures, increasing the cost and the preparation time of samples. Other analytical methods for the determination of 4(5)MEI, include capillary electrophoresis, paper spray mass spectrometry, micellar electrokinetic chromatography, high-performance cation exchange chromatography, fluorescence-based immunochromatographic assay, and a fluorescent probe.

Simultaneous Detection of Seven Alternaria Toxins in Mixed Fruit Puree by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with a Modified QuEChERS

The presence of Alternaria toxins (ATs) in fruit purees may cause potential harm to the life and health of consumers. As time passes, ATs have become the key detection objects in this kind of food. Based on this, a novel and rapid method was established in this paper for the simultaneous detection of seven ATS (tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene, tentoxin, altenusin, and altertoxin I) in mixed fruit purees using ultra-high performance liquid chromatography-tandem mass spectrometry. The sample was prepared using the modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method to complete the extraction and clean-up steps in one procedure. In this QuEChERS method, sample was extracted with water and acetonitrile (1.5% formic acid), then salted out with NaCl, separated on an ACQUITY UPLC BEH C₁₈ with gradient elution by using acetonitrile and 0.1% formic acid aqueous as eluent, and detected by UPLC-MS/MS under positive (ESI⁺) and negative (ESI⁻) electrospray ionization and MRM models. Results showed that the seven ATs exhibited a good linearity in the concentration range of 0.5–200 ng/mL with R² > 0.9925, and the limits of detection (LODs) of the instrument were in the range of 0.18–0.53 μg/kg. The average recoveries ranged from 79.5% to 106.7%, with the relative standard deviations (RSDs) no more than 9.78% at spiked levels of 5, 10, and 20 μg/kg for seven ATs. The established method was applied to the determination and analysis of the seven ATs in 80 mixed fruit puree samples. The results showed that ATs were detected in 31 of the 80 samples, and the content of ATs ranged from 1.32 μg/kg to 54.89 μg/kg. Moreover, the content of TeA was the highest in the detected samples (23.32–54.89 μg/kg), while the detection rate of Ten (24/31 samples) was higher than the other ATs. Furthermore, the other five ATs had similar and lower levels of contamination. The method established in this paper is accurate, rapid, simple, sensitive, repeatable, and stable, and can be used for the practical determination of seven ATs in fruit puree or other similar samples. Moreover, this method could provide theory foundation for the establishment of limit standard of ATs and provide a reference for the development of similar detection standard methods in the future.

g-C3N4/Fe3O4 Nanocomposites as Adsorbents Analyzed by UPLC-MS/MS for Highly Sensitive Simultaneous Determination of 27 Mycotoxins in Maize: Aiming at Increasing Purification Efficiency and Reducing Time

According to known studies, numerous mycotoxins have been found simultaneously in foods and have a certain expansion toxicity, so the simultaneous detection of multiple mycotoxins is absolutely critical. In this article, multifunctional magnetic g-C₃N₄/Fe₃O₄ nanocomposites have been fabricated to employ as modified QuEChERS adsorbents. In addition, they were also used in conjunction with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), an accurate quantitative approach, to analyze 27 mycotoxins in maize. The improved method not only has a powerful adsorption effect on the complex matrix by g-C₃N₄/Fe₃O₄ but also enables magnetic separation from the sample solution. Experiments proved that this method can exhibit good linearity under the appropriate and optimal external environment (r² ≥ 0.9954), high sensitivity (the threshold of detection limit is 0.0004-0.6226 μg kg^-1, and the threshold of quantification limit is 0.0014-2.0753 μg kg^-1), adequate recoveries (77.81-115.21%), and excellent repeatability (with a threshold of intraday precision of 1.5-10.8% and interday precision in the range of 2.9-12.5%). In practice this method has been used to evaluate a variety of mycotoxins in maize specimens, and certain actual outcomes have been achieved.

Combination of solid-phase extraction with microextraction techniques followed by HPLC for simultaneous determination of 2-methylimidazole and 4-methylimidazole in beverages

A sensitive analytical method for the monitoring 2-methylimidazole and 4-methylimidazole (2-MI and 4-MI) is desirable due to their carcinogenic property. Here, we propose a highly sensitive method basing on the combination of solid-phase extraction and dispersive liquid-liquid microextraction techniques followed by high-performance liquid chromatography to simultaneously determine 2-MI and 4-MI in beverages. Dansyl chloride was used as a derivatizing reagent. Microextraction parameters were optimized by Plackett-Burman design and response surface methodology. Results show that derivatization led to significant improvements in chromatographic behavior for 2-MI and 4-MI due to increased hydrophobicity. The method shows good linearity (R² ≥ 0.9985), satisfactory precision (%RSD ≤ 8.3%) and low limit of quantification (20 ng/mL), and was successfully applied to determine 2-MI and 4-MI in carbonated drinks, beers and energy drinks, achieving satisfactory recoveries (85-101%). This method provides a potential for routine analysis of 2-MI and 4-MI at the nanogram per milliliter level in beverages.