Effects of seasoning addition and cooking conditions on the formation of free and protein-bound heterocyclic amines and advanced glycation end products in braised lamb

The accumulation of heterocyclic amines (HAs) and advanced glycation end products (AGEs) in thermally processed meats has been arising safety concerns. The effects of cooking conditions and seasoning addition on the formation of HAs and AGEs in Chinese traditional braised lamb were investigated by UPLC-MS/MS analysis. Soy sauce significantly increased the formation of HAs and AGEs, among which light soy sauce had the greatest promoting effect (69.45-15300.62 %). Conversely, spices inhibited HAs and AGEs formation, the inhibition rate of free HAs and AGEs reached 22.06-34.72 % when using 70 % ethanol extract. Hot blanching treatment and adding soy sauce and spices at a later stage could significantly suppress HAs and AGEs production. Flavonoids, including galangin, hesperidin, narirutin, etc., were identified as key effectors in spices. These findings help to promote awareness of the formation of HAs and AGEs in braised lamb and provide valuable insights for optimizing processing techniques to minimize their production.

Mechanism of aroma enhancement methods in accelerating Congou black tea acidification subjected to room temperature storage

Acidification of aroma-enhanced black tea during storage was studied. UPLC-Q-TOF/MS (Ultra Performance Liquid Chromatography and Quadrupole-Time of Flight Mass Spectrometer) and HPLC (High-Performance Liquid Chromatography) analysis of non-volatile substances and organic acids revealed a decrease of soluble sugars and amino acids in aroma-enhanced black tea, while an increase in organic acids such as oxalic acid, malic acid and quinic acid. Further in vitro experiments indicated that the acidification of aroma-enhanced tea during storage can be attributed to decomposition of sugars and amino acids by heating, oxidation of aromatic aldehydes. Meanwhile, the amino acids, catechins, soluble sugars and flavonoids that constitute the taste of black tea are further reduced, changing the taste composition of tea infusion and further increasing its acidity. This study revealed the reasons for black tea acidification during aroma enhancement and storage and provided a theoretical basis for improving black tea quality.

Aromatic amine antioxidants (AAs) and p-phenylenediamines-quinones (PPD-Qs) in e-waste recycling industry park: Occupational exposure and liver X receptors (LXRs) disruption potential

Recently, evidence of aromatic amine antioxidants (AAs) existence in the dust of the electronic waste (e-waste) dismantling area has been exposed. However, there are limited studies investigating occupational exposure and toxicity associated with AAs and their transformation products (p-phenylenediamines-quinones, i.e., PPD-Qs). In this study, 115 dust and 42 hand wipe samples collected from an e-waste recycling industrial park in central China were analyzed for 19 AAs and 6 PPD-Qs. Notably, the median concentration of ∑6PPD-Qs (1,110 ng/g and 1,970 ng/m2) was significantly higher (p < 0.05, Mann-Whitney U test) than that of ∑6PPDs (147 ng/g and 34.0 ng/m2) in dust and hand wipes. Among the detected analytes, 4-phenylaminodiphenylamine quinone (DPPD-Q) (median: 781 ng/g) and 1,4-Bis(2-naphthylamino) benzene quinone (DNPD-Q) (median: 156 ng/g), were particularly prominent, which were first detected in the e-waste dismantling area. Occupational exposure assessments and nuclear receptor interference ability, conducted through estimated daily intake (EDI) and molecular docking analysis, respectively, indicated significant occupational exposure to PPD-Qs and suggested prioritized Liver X receptors (LXRs) disruption potential of PPDs and PPD-Qs. The study provides the first evidence of considerable levels of AAs and PPD-Qs in the e-waste-related hand wipe samples and underscores the importance of assessing occupational exposure and associated toxicity effects.

Qualitative and quantitative assessment of key aroma compounds, advanced glycation end products and heterocyclic amines in different varieties of commercially roasted meat products

Studies on the interactions and links between aroma and hazardous compounds were inadequately investigated. A complete analysis was conducted on the key aroma compounds, typical hazardous compounds and their precursors in 25 samples of roasted meats. Forty-nine aroma compounds were identified as essential odorants with odor-activity values exceeds 1. Nε-carboxymethyl lysine (CML, 11.78-49.32 μg/g) and Nε-carboxyethyl lysine (CEL, 8.48-171.00 μg/g) were identified as representative advanced glycation end products (AGEs) of meats with high concentrations. Harman and Norharman were typical heterocyclic aromatic amines. Meanwhile, correlation analysis indicated that aldehyde and alcohols showed a negative correlation with AGEs (p < 0.01), while pyrazines might affect the formation of Harman and Norharman. The furaldehyde, 1-hexanol, 2, 4-Decadienal, AGEs, and creatine were regarded as potential biomarkers that distinguished different roasted meat products. Therefore, the study could provide new insights for synergistic regulation of aroma and hazardous compounds in roasted meat products.

Attenuation of heterocyclic amine formation and lipid and protein oxidation in air-fried fish fillets by marination with selected legume seed extracts

The present study aimed to investigate the potential of marination with extracts prepared from five legume seeds on heterocyclic amine (HA) formation in chemical models and air-fried fish fillets. In terms of total HAs, clove seed marinade (CSM) was found with the maximum inhibitory effect (43.98 %), followed by tamarind seed marinade (TSM) (40.26 %), fenugreek seed marinade (FSM) (39.07 %), acacia seed marinade (ASM) (37.99 %), and black bean seed marinade (BSM) (29.95 %). In particular, at higher levels (3 mg/mL, 4 mg/mL), CSM and FSM achieved the greatest mitigating effect against 4,8-DiMeIQx, 7,8-DiMeIQx, and MeIQx. Furthermore, all marinades were effective in lowering thiobarbituric acid-reactive substances (TBARS) and carbonyl and retaining thiol content relative to the control. PCA analysis revealed that higher levels of ASM, BSM, and FSM had better mitigating effect against IQ and MeIQx formation, whereas Pearson correlation shows that TBARS and carbonyl were positively correlated to HAs.

Structural elucidation of derivatives of polyfunctional metabolites after methyl chloroformate derivatization by high-resolution mass spectrometry gas chromatography. Application to microbiota metabolites

Metabolomics has become an essential discipline in the study of microbiome, emerging gas chromatography coupled to mass spectrometry as the most mature, robust, and reproducible analytical technique. Silylation is the most widely used chemical derivatization strategy, although it has some limitations. In this regard, alkylation by alkyl chloroformate offers some advantages, such as a rapid reaction, milder conditions, better reproducibility, and the generation of more stable derivatives. However, commercial spectral libraries do not include many of the alkyl derivatives, mainly for polyfunctional metabolites, which can form multiple derivatives. That introduces a huge bias in untargeted metabolomics leading to common errors such as duplicates, unknowns, misidentifications, wrong assignations, and incomplete results from which non-reliable findings and conclusions will be retrieved. For this reason, the purpose of this study is to overcome these shortcomings and to expand the knowledge of metabolites in general and especially those closely related to the gut microbiota through the thorough study of the reactivity of the different functional groups in real matrix derivatized by methyl chloroformate, a common representative alkylation reagent. To this end, a systematic workflow has been developed based on exhaustive structural elucidation, along with computational simulation, and taking advantage of the high sensitivity and high-resolution gas chromatography-mass spectrometry. Several empirical rules have been established according to chemically different entities (free fatty acids, amino acids, polyols, sugars, amines, and polyfunctional groups, etc.) to predict the number of derivatives formed from a single metabolite, as well as their elution order and structure. In this work, some methyl chloroformate derivatives not previously reported as well as the mechanisms to explain them are given. Extremely important is the interconversion of E- and Z- geometric isomers of unsaturated dicarboxylic acids (case of fumaric-maleic and case of citraconic-mesaconic acids), or the formation of cycled derivatives for amino acids, as well as common metabolites, as in the case of serine and cysteine, and many others.

Selenium content, chemical composition and volatile components of essential oil and hydrosol from flowers of Cardamine violifolia

Cardamine violifolia is a unique selenium hyperaccumulating vegetable in China, but its flowers are commonly wasted in large-scale cultivation. To better utilize this resource, this study explored the selenium content, chemical composition, and volatile organic compounds (VOCs) of hydro-distilling essential oil (EO) and hydrosol from C. violifolia flowers. ICP-MS results indicated that the EO and hydrosol contained selenium reaching 13.66±2.82 mg/kg and 0.0084±0.0013 mg/kg, respectively. GC-MS analysis revealed that organic acids, hydrocarbons, and amines were the main components of EO. Additionally, benzyl nitrile, benzaldehyde, benzyl isothiocyanate, benzyl alcohol, megastigmatrienone, and 2-methoxy-4-vinylphenol also existed in considerable amounts. The hydrosol extract had fewer components, mainly amines. HS-SPME-GC-MS corresponded to the composition analysis and aromatic compounds were the prevalent VOCs, while HS-GC-IMS primarily identified C2-C10 molecular alcohols, aldehydes, ethers, and sulfur-containing compounds. This study first described the chemical composition and VOC profiles of EO and hydrosol from selenium hyperaccumulating plant.

Comparative metabolomic analysis and antigenicity comparison of cow milk and enzymatically treated cow milk

BACKGROUND

Amino acids (AAs) are important protein building blocks that play a critical role in the function of the immune system. However, comprehensive comparative metabolomics and antigenicity analyses of cow milk (CM) and enzymatically treated CM are relatively scarce. This study analyzed the AAs in the CM and Flavourzyme-treated milk groups (FT), and their antigenicity was also explored.

RESULTS

Overall, 50 AAs were detected in the CM and FT groups, with 23 significantly different AAs. The interaction network of these significantly different AAs was analyzed, and 34 significantly different metabolic pathways were found to be involved. It was also found that the antigenicity of the FT group was significantly reduced in comparison with that of the CM group.

CONCLUSION

These results enhance our understanding of AAs and antigenicity regarding CM and FT, and provide new ideas and directions for the development of high-quality hypoallergenic dairy products. © 2023 Society of Chemical Industry.

Integrating Post-Ionization Separation via Differential Mobility Spectrometry into Direct Analysis in Real Time Mass Spectrometry for Toy Safety Screening

Direct analysis in real time (DART) enables direct desorption and ionization of analytes, bypassing the time-consuming chromatographic separation traditionally required for mass spectrometry (MS) analysis. However, DART-MS suffers from matrix interference of complex samples, resulting in compromised detection sensitivity and quantitation accuracy. In this study, DART-MS was combined with differential mobility spectrometry (DMS) to provide an additional dimension of post-ionization ion mobility separation within a millisecond time scale, compensating for the lack of separation in DART-MS analysis. As proof-of-concept, primary aromatic amines (PAAs), a class of potentially hazardous chemicals, were analyzed in various toy products, including bubble solutions, finger paints, and plush toys. In addition to commercial Dip-it glass rod and metal mesh sampling tools, a customized rapid extractive evaporation device was designed for the accelerated extraction and sensitive analysis of solid toy samples. The incorporation of DMS in DART-MS analysis enabled the rapid separation and differentiation of isomeric analytes, leading to improved accuracy and reliability. The developed protocols were optimized and validated, achieving good linearity with correlation coefficients greater than 0.99 and acceptable repeatability with relative standard deviations less than 10%. Moreover, satisfactory sensitivity was realized with limits of detection and quantitation ranges of 0.2-5 and 1-20 μg/kg (μg/L) for the 11 PAA analytes. The established methodology was applied for the analysis of real toy samples (n = 18), which confirmed its appealing potential for toy safety screening and consumer health protection.

GC-MS Analysis of Primary Aromatic Amines Originated From Azo Dyes in Commercial Textile or Leather Products Using Helium Alternative Carrier Gases

BACKGROUND

In recent years, due to the global shortage of helium gas, the development of gas chromatography (GC) analytical methods using alternatives to helium carrier gases is necessary.

OBJECTIVE

The objective of this study was to examine the applicability of hydrogen and nitrogen as alternative carrier gases using the test method for azo compounds in the Act on Control of Household Products Containing Harmful Substances of Japan.

METHOD

The gas chromatograph mass spectrometer (GC-MS) analytical method using hydrogen and nitrogen as alternative carrier gases was compared with a method using helium for 26 primary aromatic amines (PAAs) originated from azo dyes.

RESULTS

When hydrogen and nitrogen were used as carrier gases under the same conditions used during analysis using helium (same column, gas flow rate, oven temperature conditions, etc.), sufficient peak separation of 26 PAAs was obtained. The sensitivities of the methods using helium and hydrogen were comparable, whereas the sensitivity was lower when nitrogen was used, with the detection limits ranging from 1/220 to 1/25. However, all carrier gases achieved quantification at concentrations below the standard value (30 μg/g) of the Act on Control of Household Products Containing Harmful Substances, and the results were in agreement with the standard value for the target product.

CONCLUSIONS

Our results indicated that hydrogen or nitrogen can be used as alternative carrier gases to helium for GC-MS analysis of azo compounds producing specific aromatic amines.

HIGHLIGHTS

Using hydrogen or nitrogen as an alternative carrier gas to helium, azo compounds could be quantified with excellent accuracy.

Effects of volatile organic compounds of smoke from different woods on the heterocyclic amine formation and quality changes in pork patty

This study investigated the effects of smoke derived from cypress (CY), mulberry (MU), metasequoia (ME), pine (PI), and camphor (CA) on the heterocyclic aromatic amines (HAs), flavor, and sensory attributes of smoked pork patty. The results showed that the smoke derived from the five kinds of wood and the flavor of the corresponding smoked meat were classified into three types. Moreover, the smoke of CY and PI, and the smoke of MU and ME can be classified into one category respectively, which significantly improved the flavor of the smoked meat. Both free and protein-bound HAs were detected in smoked meat, while the smoking process significantly increased the HAs content, especially free Norharman (3.26 ng/g in control meat, and 82.24 ng/g in meat smoked with CY). Correlation analysis showed that various volatile organic compounds (VOCs) and HAs were closely associated. Future research should pay attention to the VOCs in smoked meat including vanillin, Close attention should be paid to tridecane and crotonic acid, as well as tetradecane and α-Dehydro-ar-himachalene in smoke, which were consistently correlated with various HAs and may participate in HAs formation. These results may reveal how the smoking process influences the formation of HAs and which factors should be targeted to inhibit HAs in smoked meat products.

Effects of soy protein and its hydrolysates on the formation of heterocyclic aromatic amines in roasted pork

This study investigated the influence mechanism of soy protein and its hydrolysates (under three different degree of hydrolysis) on formation of heterocyclic aromatic amines (HAAs) formation in roasted pork. The results showed that 7S and its hydrolysates significantly inhibited the formation of quinoxaline HAAs, and the maximum inhibitory rate of MeIQx, 4,8-MeIQx, and IQx was 69%, 79%, and 100%, respectively. However, soy protein and its hydrolysates could promote the formation of pyridine HAAs (PhIP, and DMIP), its content increased significantly with the increase in the degree of hydrolysis of the protein. The content of PhIP increased 41, 54, and 165 times with the addition of SPI, 7S, and 11S at 11% degree of hydrolysis, respectively. In addition, they promoted the formation of β-carboline HAAs (Norharman and Harman), in a manner similar with that of PhIP, especially the 11S group. The inhibitory effect on quinoxaline HAAs was probably correlated with DPPH radical scavenging capacity. Nevertheless, the promotive effect on other HAAs might be related to the high levels of free amino acids and reactive carbonyls. This research may provide recommendation for the application of soy protein in high-temperature meat products.

The Flexibility of β-Content, γ-Confidence Tolerance Intervals to Qualimetry a Simultaneous 22 Aromatic Amines Derived from Azo Dyes in Fabric Using a Sensitive GC-MS Technique

BACKGROUND

Azo dyes are among the most widely used dyes in the textile industry, releasing a series of carcinogenic aromatic amines that can be absorbed through the skin.

OBJECTIVE

This work aims to show that 22 azo dye amines in a textile matrix can be quantified using a GC-MS method.

METHODS

Based on the notion of total error and β-content, γ-confidence tolerance intervals (β,γ-CCTI), a chemometric approach known as the "uncertainty profile" has been used to completely validate a GC-MS method for the simultaneous assay of 22 azo amines in fabrics. According to International Organization for Standardization (ISO) in ISO 17025 guidelines, analytical validation and measurement uncertainty estimates have evolved to be two main principles for ensuring the accuracy of analytical results and controlling the risk associated with their use.

RESULTS

The calculated tolerance intervals allowed for the determination of the uncertainty limits at each concentration level. These limits when compared to the acceptable limits show that a significant portion of the expected outcomes is in conformity. Additionally, the relative expanded uncertainty values, calculated with a proportion of 66.7% and a 10% risk, do not exceed 27.7, 12.2, and 10.9% for concentration levels 1, 15, and 30 mg/L, respectively.

CONCLUSION

The capability and flexibility of the β-content, γ-confidence intervals have been established through the use of this innovative approach to carrying out qualimetry of the GC-MS method depending on the behavior, required conformity proportion, and acceptable tolerance limits of each amine.

HIGHLIGHTS

An efficient GC-MS technique for the simultaneous determination of 22 azo amines in a textile matrix has been developed. Analytical validation using a new strategy based on the uncertainty concept is reported, uncertainty associated to measurement results is estimated, and the applicability of our approach to the GC-MS method is investigated.

Sensory acceptability of antioxidant-based formulations dedicated to mitigate heterocyclic aromatic amines in cooked meat

In a previous work, we studied the inhibition of heterocyclic aromatic amine formation by natural ingredients rich in antioxidants: caper, oregano, wine and green tea. This present work aimed to assess the sensory impact of the addition of these ingredients in ground beef patties. The best liked formulations were determined by a hedonic scoring. Caper and oregano were not significantly different from the standard, the most appreciated, due to their congruency with cooked meat. Direct dissimilarity assessment was performed to evaluate the overall, gustative and odor differences between formulations. Olfactive differences were evidenced as key drivers of these differences. Standard and caper were close while oregano was found significantly different from them. A fast sensory profiling permitted to evidence that aromatic plant note was discriminant for oregano formulation. Gas chromatography-mass spectrometry/multibooth olfactometry identified the distinctive odor-active compounds of the formulations as pyrazines and sulfide for oregano formulation and ester for caper formulation.

Development and evaluation of a novel fluorescent chiral derivatization reagent DBD-S-M-Pro: first observation of four chiral amino acids in human hair

This study reports a novel fluorescent chiral derivatization reagent, 4-(N,N-dmethylaminosulfonyl)-2,1,3-benzoxadiazole-(2-succinimidoxy)-trans-2-methyl-L-proline (DBD-S-M-Pro), with a benzoxadiazole structure containing an N-hydroxysuccinimide activation group. DBD-S-M-Pro targets chiral amino-functional compounds under alkaline conditions without a condensation agent. Gradient elution was performed on a BEH C18 (100 × 2.1 mm, 1.7 μm) column with a mobile phase of 0.05% formic acid (FA) in 10 mM ammonium acetate (CH₃COONH₄) and 0.1% FA in acetonitrile or methanol. The efficiency of the chiral resolution was evaluated under excitation and emission wavelengths of 450 nm and 560 nm, respectively. The 19 chiral amino acids were separated in the range of 1.45-14.84. The resolutions of almost all DL-amino acids exceeded 1.5; the exceptions were serine (Ser) and lysine (Lys), with resolutions of 1.45 and 1.46, respectively. In addition, a new approach was devised for the simultaneous analysis of four chiral amino acids (DL-Glu, DL-Ala, DL-Val, and DL-Phe) in human hair. These amino acids were analyzed in the range of 12.5-400 pmol, with R² ≥ 0.9990, limits of detection (S/N = 3) of 4-10 pmol, and intraday and interday precisions of 0.57-6.23%. The average spikes in the hair recoveries were 89.76-111.54%, and the matrix effects were 92.47-102.40%. Next, the contents of free chiral amino acids in the hair samples of 10 healthy volunteers (five males and five females) were analyzed with this method, and the differences were compared. The developed DBD-S-M-Pro provides a novel strategy for the sensitive determination of free chiral amino acids in living organisms.

Advancing metabolic networks and mapping updated urinary metabolic fingerprints after exposure to typical carcinogenic heterocyclic aromatic amines

Heterocyclic aromatic amines (HAAs) were not only present in cooked foods and cigarette smoke, but also measured in airborne particles and diesel-exhaust particles. Typical HAAs have been reported to induce carcinogenicity and metabolic disturbances, but how these hazardous compounds interfere with metabolic networks by regulating metabolic pathways and fingerprinting signature metabolites as biomarkers remains ambiguous. We developed an advanced strategy that adopted chemical isotope labeling ultrahigh-performance liquid chromatography coupled to quadrupole-Orbitrap high-resolution mass spectrometry for urinary nontargeted metabolomics analysis to gain new insight into in vivo physiological responses stimulated by exposure to typical HAAs. Rats were orally administered with a single dose of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) or 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) (1 and 10 mg/kg bw) and their D₃-isotopic compounds, respectively, and urine samples were then continuously collected within 36 h. Metabolomics data were acquired and processed by classical multivariate statistical analysis, while urinary metabolites were further identified and characterized according to mass spectrometric fragmentation rules, time- and dose-dependent profiles, and calibration of synthesized standards. We monitored 23 and 37 urinary metabolites as the biotransformation products of PhIP and MeIQx, respectively, and first identified demethylated metabolites of PhIP, tentatively named 2-amino-6-phenylimidazo[4,5-b]pyridine, and dihydroxylation products of classical HAAs as short-term biomarkers of exposure to further unravel the metabolic networks. In addition, our findings revealed that both HAAs significantly disturb histidine metabolism, arginine and proline metabolism, tryptophan metabolism, pyrimidine metabolism, tricarboxylic acid cycle, etc. Furthermore, we found that histamine, methionine, alanine, and 4-guanidinobutanoic acid could be considered potential characteristic biomarkers for the oncogenicity or carcinogenicity of both PhIP and MeIQx and screened their specific key pivotal metabolites. The current metabolomics approach is applicable in mapping updated urinary metabolic fingerprints and identifying potential specific biomarkers for HAAs-induced early tumorigenesis.

The effect of PhIP precursors on the generation of particulate matter in cooking oil fumes at high cooking temperatures and the inflammation response in human lung cells

Cooking Oil Fumes (COFs) contain carcinogenic organic substances such as polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs), of which 2-Amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) is known as mainly meat-borne carcinogens. In this work, to identify the mechanisms to induce the inflammation response in human lung cells (A549) exposed to COFs, we investigated the physicochemical and biological characteristics of COFs generated with PhIP precursors (L-phenylalanine, creatinine, and glucose) at high cooking temperatures (300 °C and 600 °C). Interestingly, we found that PhIP was not formed both at 300 °C and 600 °C, while a large number of carbon nanoparticles were generated from soybean oil containing the PhIP precursors at 600 °C. From the biological analysis, COFs generated with the PhIP precursors at 600 °C induced the most significant pro-inflammatory cytokine (IL-6). This result indicates that the particulate matter in COFs generated with the PhIP precursors above the smoke temperature is the primary factor directly affecting the lung inflammatory response rather than PhIP. This study demonstrates for the first time a novel principle of the inflammatory response that the PhIP precursors can aggravate lung injury by affecting the physical properties of COFs depending on cooking temperature. Therefore, our finding is a significant result of overcoming the bias in previous studies focusing only on the chemical toxicity of PhIP in the inflammatory response of COFs.

Assessment of heterocyclic aromatic amines contents in flamed and braised chicken in Burkina Faso

The nutritional status of meat is tarnished by its association with the induced cooking contaminants. The aim of this study was to assess the heterocyclic aromatic amines profile and contents in processed chicken in Burkina Faso. Eight polar and apolar heterocyclic aromatic amines (HAAs) including 2-mino-3-methylimidazo[4,5-f]quinolone (IQ), 3-amino-1,4-dimethyl-5H-pyrido[4, 3-b]indole (Trp-P1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P2), 2-mino-9H-pyrido-[2,3-b]indole (AαC), 2-amino-1-methyl-6-phenylimidazo[4, 5- ]pyridine (PhIP), 2-amino-3-methyl-9H-pyrido[2,3-b] indole (MeAαC), 2-amino-3,4,8-rimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) and 2-amino-3,8-imethylimidazo[4,5-]quinoxaline (MeIQx) were screened by high performance liquid chromatography from 29 samples of flamed chicken and 66 samples of braised chicken collected in Ouagadougou city. Apolar HAAs and polar HAAs were respectively 12 and 3 times more abundant in flamed chickens (32.66±10 and 3.48±10.39 ng/g, respectively) than in braised chickens (2.70±9.67 and 0.92 ng/g, respectively). The maximum levels of AαC were in the same proportions in flamed (12.01 ng/g) and braised chickens (14.13 ng/g). Flamed chicken had the highest Trp-P1 content (530.31 ng/g). The 4,8-DiMeIQx was not detected in braised chicken. The AαCs were more abundant in flamed than in braised chicken. The profile and the contents of the HAAs in processed chicken are related to cooking methods. Because of the high variability observed on the obtained concentrations, investigations on the contents of precursors in raw chicken, the effect of marinating ingredients on the formation of HAAs are needed.

Position-specific carbon isotope analysis of serine by gas chromatography/Orbitrap mass spectrometry, and an application to plant metabolism

RATIONALE

Position-specific ¹³ C/¹² C ratios within amino acids remain largely unexplored in environmental samples due to methodological limitations. We hypothesized that natural-abundance isotope patterns in serine may serve as a proxy for plant metabolic fluxes including photorespiration. Here we describe an Orbitrap method optimized for the position-specific carbon isotope analysis of serine to test our hypothesis and discuss the generalizability of this method to other amino acids.

METHODS

Position-specific carbon isotope ratios of serine were measured using a Thermo Scientific™ Q Exactive™ GC Orbitrap™. Amino acids were hydrolyzed from Arabidopsis biomass, purified from potential matrix interferences, and derivatized alongside standards. Derivatized serine (N,O-bis(trifluoroacetyl)methyl ester) was isolated using gas chromatography, trapped in a reservoir, and purged into the electron ionization source over tens of minutes, producing fragment ions containing different combinations of atoms from the serine-derivative molecule. The ¹³ C/¹² C ratios of fragments with monoisotopic masses of 110.0217, 138.0166, and 165.0037 Da were monitored in the mass analyzer and used to calculate position-specific δ¹³ C values relative to a working standard.

RESULTS

This methodology constrains position-specific δ¹³ C values for nanomole amounts of serine isolated from chemically complex mixtures. The δ¹³ C values of fragment ions of serine were characterized with ≤1‰ precisions, leading to propagated standard errors of 0.7-5‰ for each carbon position. Position-specific δ¹³ C values differed by up to ca 28 ± 5‰ between serine molecules hydrolyzed from plants grown under contrasting pCO₂ , selected to promote different fluxes through photosynthesis and photorespiration. The method was validated using pure serine standards characterized offline.

CONCLUSIONS

This study presents the first Orbitrap-based measurements of natural-abundance, position-specific carbon isotope variation in an amino acid isolated from a biological matrix. We present a method for the precise characterization of isotope ratios in serine and propose applications probing metabolism in plants. We discuss the potential for extending these approaches to other amino acids, paving the way for novel applications.

Improved Ion Mobility Separation and Structural Characterization of Steroids using Derivatization Methods

Steroids are an important class of biomolecules studied for their role in metabolism, development, nutrition, and disease. Although highly sensitive GC- and LC-MS/MS-based methods have been developed for targeted quantitation of known steroid metabolites, emerging techniques including ion mobility (IM) have shown promise in improved analysis and capacity to better identify unknowns in complex biological samples. Herein, we couple LC-IM-MS/MS with structurally selective reactions targeting hydroxyl and carbonyl functional groups to improve IM resolution and structural elucidation. We demonstrate that 1,1-carbonyldiimidazole derivatization of hydroxyl stereoisomer pairs such as testosterone/epitestosterone and androsterone/epiandrosterone results in increased IM resolution with ΔCCS > 15%. Additionally, performing this in parallel with derivatization of the carbonyl group by Girard's Reagent P resulted in unique products based on relative differences in number of each functional group and C17 alkylation. These changes could be easily deciphered using the combination of retention time, collision cross section, accurate mass, and MS/MS fragmentation pattern. Derivatization by Girard's Reagent P, which contains a fixed charge quaternary amine, also increased the ionization efficiency and could be explored for its potential benefit to sensitivity. Overall, the combination of these simple and easy derivatization reactions with LC-IM-MS/MS analysis provides a method for improved analysis of known target analytes while also yielding critical structural information that can be used for identification of potential unknowns.

Influence of meteorological parameters and oxidizing capacity on characteristics of airborne particulate amines in an urban area of the Pearl River Delta, China

Nine amine species in atmospheric particles during haze and low-pollution days with low and high relative humidity (RH) were analyzed in urban Guangzhou, China. The mean concentrations of total measured amines (Ʃamines) in fine particles were 208 ± 127, 63.7 ± 21.3, and 120 ± 20.1 ng m^-3 during haze, low pollution-low RH (LP-LRH), and low pollution-high RH (LP-HRH) episodes, respectively. The dominant amine species were methylamine (MA), dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA), which in total accounted for 82-91% of the Ʃamines during different pollution episodes. The contributions of Ʃamines-C to water-soluble organic carbon (WSOC) and Ʃamines-N to water-soluble organic nitrogen (WSON) were 1.52% and 2.49% during haze, 1.24% and 1.96% during LP-LRH, and 2.00 and 2.98% during LP-HRH days, respectively. The mass proportion of Ʃamines in fine particles was higher during LP-HRH periods (0.19%) than during haze and LP-LRH periods (0.16%). The mass proportion of DBA in Ʃamines increased from 7% during haze and LP-LRH episodes to 25% during LP-HRH episodes. Compared with other amines, DBA showed a stronger linear relationship with RH (r = 0.867, p < 0.01), which demonstrates its high sensitivity to high RH conditions. Meteorological parameters (including RH, the mixed layer depth, wind speed and temperature), the oxidizing capacity (ozone concentration), and gaseous pollutants (NO_x and SO₂) correlated with amines under different pollution conditions. Under high RH, acid-base reactions were the dominant pathway for the gas-to-particle distribution of amines in urban areas, while direct dissolution dominated in the background site. To our knowledge, this study is the first attempt to conduct in situ measurements of particulate amines during different pollution conditions in China, and further research is needed to in-depth understanding of the influence of amines on haze formation.

Levels of nitramines and nitrosamines in lake drinking water close to a CO2 capture plant: A modelling perspective

While CO₂ capture is considered a key climate change mitigation option, we must ensure that global implementation occurs without causing harm to the local environment and the human health. The most mature option for capture is using amines, which however, is associated with a risk of contaminating nearby drinking water sources with carcinogenic nitramines (NAs) and nitrosamines (NSAs). Here we present the first process-based simulation of NAs and NSAs in a catchment-lake system with the input of previously modelled atmospheric deposition rates. Considering full-scale CO₂ capture at the Oslo waste incineration plant in Norway, future (∼10 y) levels in a nearby lake approach the national drinking water limit. We further quantified the effect of hydrological and biogeochemical processes and identified those with the highest sensitivity (NA biodegradation). The uncertainty of the results is presented by a probabilistic distribution (Monte Carlo analysis), incorporating variability in catchment, lake, and literature NA and NSA parameter values. This modelling tool allows for the site-specific assessment of the abovementioned risks related to amine-based CO₂ capture and aspires to contribute to the sound evaluation of costly amine emission reduction measures.

Chemical composition and sources of amines in PM2.5 in an urban site of PRD, China

Atmospheric amines have attracted increasing attention due to their significant impact on new particle formation, particle hygroscopicity and particle optical properties. In this study, four low-molecule-weight amines were detected from PM_2.5 filter samples collected at an urban site of Pearl River Delta (PRD) region of China in 2018 autumn. During the campaign, the mass concentrations of ambient particulate methylamine (MA, CH₃NH₂), dimethylamine (DMA, (CH₃)₂NH), trimethylamine (TMA, (CH₃)₃N), and diethylamine (DEA, (C₂H₅)₂NH) were quantified at daily or 12-h resolution using an optimized Ion Chromatograph (IC) method. The total measured amine concentration was 297 ± 209 ng/m³, which can account for 0.76 ± 0.33% of PM_2.5 mass concentrations. The particulate amines in PRD urban area were dominated by MA (243 ± 179 ng/m³), accounting for over 80% of total amines, then followed by DMA (49 ± 30 ng/m³, 16.5%), TMA (4 ± 2 ng/m³) and DEA (1 ± 1 ng/m³). Based on the correlation analysis, MA and DMA mainly presented as nitrate and sulfate salts. We speculate the amines tend to react with gas-phase HNO₃ or particle-phase nitrate to form particulate amine salts via local process in Guangzhou. As the relative humidity (RH) increased, enhanced partitioning of amine towards the particle phase was observed. Using approach of multiple linear regression, 71% of the particulate amines in PRD urban site could be explained by acid-base process and the rest by primary emissions from combustion sources (29%).

Heterocyclic Aromatic Amines and Risk of Kidney Stones: A Cross-Sectional Study in US Adults

Background

Heterocyclic aromatic amines (HAAs) are a group of harmful substances produced while cooking meat at high temperatures. This study aimed to investigate the relationship between HAAs and the occurrence of kidney stones.

Methods

Data on the level of four HAAs, including 2-Amino-9H-pyrido [2, 3-b] indole (A-α-C), 1-Methyl-9H-pyrido [3, 4-b] indole (Harman), 9H-Pyrido [3, 4-b] indole (Norharman), and 2-Amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine (PhIP), in the urine from adult participants were extracted from the 2013–2014 NHANES database. Propensity score matching (PSM) was used to balance confounding variables between the stone former and non-stone former groups, and logistic regression analysis was performed to analyze the relationship between HAAs and the occurrence of kidney stones.

Results

Of the 1,558 eligible participants, a history of kidney stones was self-reported by 140 (9.0%). Compared to non-stone formers, stone formers had higher concentrations of A-α-C, Harman, and Norharman and lower concentrations of PhlP in urine. After adjusting for all other confounding variables, multivariate logistic regression analysis showed that the high-Harman group had a higher risk of kidney stones than the low-Harman group [adjusted odds ratios (aOR) = 1.618, 95% CI: 1.076–2.433, p = 0.021]. After PSM analysis, Harman concentration remained a risk factor for kidney stones (high-Harman group vs. low-Harman group: aOR = 1.951, 95% CI: 1.059–3.596, p = 0.032).

Conclusion

Increased urinary Harman concentrations are associated with an increased risk of kidney stones in the general US population.

The Unexpected Selectivity Switching from Mitochondria to Lysosome in a D-π-A Cyanine Dye

Two interesting benzothizolium-based D-π-A type hemicyanine dyes (3a-3b) with a diphenylamine (-NPh₂) donor group were evaluated for fluorescence confocal microscopy imaging ability in live cells (MO3.13, NHLF). In sharp contrast to previously reported D-π-A dyes with alkyl amine donor (-NR₂) groups (1), 3a and 3b exhibited significantly different photophysical properties and organelle selectivity. Probes 3a and 3b were nearly non-fluorescent in many polar and non-polar solvents but exhibited a bright red fluorescence (λ_em ≈ 630-640 nm) in stained MO3.13 and NHLF with very low probe concentrations (i.e., 200 nM). Fluorescence confocal microscopy-based co-localization studies revealed excellent lysosome selectivity from the probes 3a-3b, which is in sharp contrast to previously reported D-π-A type benzothiazolium dyes (1) with an alkyl amine donor group (-NR₂) (exhibiting selectivity towards cellular mitochondria). The photostability of probe 3 was found to be dependent on the substituent (R') attached to the quaternary nitrogen atom in the cyanine dye structure. The observed donor-dependent selectivity switching phenomenon can be highly useful in designing novel organelle-targeted fluorescent probes for live-cell imaging applications.

Analysis of six aromatic amines in the mainstream smoke of tobacco products

Aromatic amines are a class of carcinogenic compounds in tobacco smoke that are listed on the FDA list of harmful and potentially harmful constituents (HPHCs). A method using solid-phase microextraction-coupled to gas chromatography-triple quadrupole mass spectrometry (SPME headspace GC-MS/MS) was developed and validated for the quantitative determination of six aromatic amines, including 1-aminonaphthalene (1-AN), 2-aminonaphthalene (2-AN), 3-aminobiphenyl (3-ABP), 4-aminobiphenyl (4-ABP), o-toluidine (o-TOL), and o-anisidine (o-ANI), in the mainstream smoke of cigarettes, cigars, and heated tobacco products. The method developed here combines high sensitivity with simple sample preparation and has demonstrated satisfactory linearity for all six aromatic amines with correlation coefficients greater than 0.9994. The limits of detection range and the limits of quantitation range were 12-96 pg/mL and 41-320 pg/mL, respectively. Their recoveries and coefficients of variation (CV%) were 90-112% and 2.1-6.6%, respectively. The new SPME headspace GC/MS/MS method has been successfully applied to measure the contents of the six aromatic amines in the mainstream smoke of cigarettes, cigars, and heated tobacco products.

Influence of soybean isolate on the formation of heterocyclic aromatic amines in roasted pork and its possible mechanism

In this paper, the effects of soybean protein isolate (SPI) on the formations of five heterocyclic aromatic amines (HAAs) in roasted pork were investigated. The levels of all five HAAs improved upon addition of 2.5% of SPI (P < 0.05). With higher SPI dosage, the levels of HAA decreased after seeing an increase. Two HAAs (MeIQx and 4,8-DiMeIQx) were inhibited by 10.0% of SPI, with the inhibitory efficiencies of 7.0 % and 85.7%, respectively. After being heated, the levels of both the free amino acids and carbonyl groups in the SPI were observed significantly increased, from 55.04 μg g·SPI-1 to 91.66 μg g·SPI-1 and from 123.85 ± 13.07 to 931.78 ± 32.56, respectively (P < 0.05). Therefore, the possible promotion mechanism of the SPI was speculated that the heated SPI would provide both the HAA precursors and carbonyls, which significantly promoted the Strecker degradation and generated more HAA intermediates (P < 0.05).

Formation and Prediction of PhIP, Harman, and Norharman in Chemical Model Systems Containing Epicatechin under Various Reaction Conditions

The aim of this study was to investigate the formation rules of 1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), 1-methyl-9H-pyrido[3,4-b]-indole (Harman), and 9H-pyrido[3,4-b]-indole (Norharman) in chemical model systems containing epicatechin under various reaction conditions and establish their prediction models. The results indicated that at 100-200 °C and pH 5.5-7.5 for 10-90 min, epicatechin inhibited the formation of PhIP, Harman, and Norharman by 32-100, 1-93, and 5-98%, respectively. The exponential growth equation in the growth model with R² of 0.986-0.997, the second-order equation in the polynomial model with R² of 0.900-0.949, and the trigonometric function equation in the Fourier model with R² of 0.513-0.926 were well fitted for the formation of PhIP, Harman, and Norharman at various temperatures, times, and pHs, respectively. The calibration set (R²c) and the prediction set (R²p) of the optimal partial least squares regression prediction model was 0.74 and 0.70 for PhIP, 0.75 and 0.70 for Harman, and 0.90 and 0.91 for Norharman, respectively. The results provide theoretical support to develop technologies or equipment for the real-time synchronous monitoring of PhIP, Harman, and Norharman during meat processing.

Primary aromatic amines in indoor dust from 10 countries and associated human exposure

Although primary aromatic amines (AAs) are widely used in consumer products, little is known about their occurrence in indoor dust. A liquid chromatography - tandem mass spectrometry (LC-MS/MS) method was applied for the determination of 29 AAs and two tobacco smoke markers (nicotine and cotinine) in 256 house dust samples collected from 10 countries. Of the 29 AAs analyzed, p-anisidine, o-anisidine, 2,6-dimethylaniline (2,6-DMA), p-cresidine (p-CD), p-toluidine (p-TD), 4,4'-methylenedianiline (4,4'-MDA), ortho/meta-toluidine (o/m-TD), 4-chloroaniline (4-CA), 2,4-diaminotoluene (2,4-DAT), aniline, and 2-naphthylamine (2-NA) as well as nicotine and cotinine, were found prevalent in house dust samples. Sum median concentrations of AAs and tobacco smoke markers varied from 29.6 to 576 ng/g (overall median: 200 ng/g) and 10.8 to 2920 ng/g (415 ng/g), respectively. Among AAs, aniline was the abundant contaminant, found at median concentrations ranging from 19.6 ng/g (Colombia) to 334 ng/g (South Korea). Nicotine was detected in all indoor samples at median concentrations ranging from 9.92 ng/g (Colombia) to 2790 ng/g (India) ng/g. Concentrations of AAs in indoor dust were significantly correlated with those of nicotine. Estimated daily intake (EDI) of select AAs through the ingestion of house dust was in the range of 0.019-3.03 ng/kg-bw/day, which was five orders of magnitude below the tolerance limits.

NBD-based synthetic probes for sensing small molecules and proteins: design, sensing mechanisms and biological applications

Compounds with a nitrobenzoxadiazole (NBD) skeleton exhibit prominent useful properties including environmental sensitivity, high reactivity toward amines and biothiols (including H2S) accompanied by distinct colorimetric and fluorescent changes, fluorescence-quenching ability, and small size, all of which facilitate biomolecular sensing and self-assembly. Amines are important biological nucleophiles, and the unique activity of NBD ethers with amines has allowed for site-specific protein labelling and for the detection of enzyme activities. Both H2S and biothiols are involved in a wide range of physiological processes in mammals, and misregulation of these small molecules is associated with numerous diseases including cancers. In this review, we focus on NBD-based synthetic probes as advanced chemical tools for biomolecular sensing. Specifically, we discuss the sensing mechanisms and selectivity of the probes, the design strategies for multi-reactable multi-quenching probes, and the associated biological applications of these important constructs. We also highlight self-assembled NBD-based probes and outline future directions for NBD-based chemosensors. We hope that this comprehensive review will facilitate the development of future probes for investigating and understanding different biological processes and aid the development of potential theranostic agents.

Determination of primary aromatic amines from cooking utensils by capillary electrophoresis-tandem mass spectrometry

This paper describes a fast, sensitive, environment-friendly method for the determination of 19 primary aromatic amines (PAAs) in cooking utensils by capillary zone electrophoresis coupled with tandem mass spectrometry. The best electrophoretic separation of PAAs was obtained in 0.1 mol l^-1 formic acid (pH 2.4) as the background electrolyte, fused silica capillary (67 cm) with a run time below 6 min. The proposed method presented a linear calibration with correlation coefficients higher than 0.99 and reproducibility in a range of 1-25%. Limits of detection were in the range of 0.2-1.3 μg kg^-1 and recoveries were in a range of 85-120% for all the PAAs. The validated method was employed to determine PAAs on 36 samples of cooking utensils using acetic simulant. The results showed that 4,4'-diaminodiphenylmethane and aniline being the most frequently found PAAs in these samples and 28% of cooking utensils were not compliant.

The presence of polycyclic aromatic hydrocarbons and heterocyclic aromatic amines in barbecued meatballs formulated with different animal fats

The formations of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HAAs) in barbecued meatballs formulated with different animal fats [beef intermuscular and/or sheep tail (ST)] were investigated. Meatballs were also analyzed in terms of some qualitative and quantitative properties. From perspective of nutrition, meatballs formulated with ST fat at level 10% contained the highest ratios of linoleic acid (2.29%), ∑PUFA (2.52%), and ∑PUFA/∑SFA (0.05). Animal fat type had no significant effect on total HAAs amount of the samples and total HAAs amount was ranged between 1.35 and 2.91 ng/g. On the other hand, the usage of different animal fat significantly affected amount of BaP and PAH4, and the levels of BaP and PAH4 were ranged between 2.33-4.30 and 8.41-15.48 ng/g, respectively. From perspective of health risk, it can be noted that the meatballs formulated with ST fat at level 10% are more risky due to their total amounts of food toxicants.

Effects of ten vegetable oils on heterocyclic amine profiles in roasted beef patties using UPLC-MS/MS combined with principal component analysis

Soybean oil (SBO), rapeseed oil (RSO), peanut oil (PO), corn oil (CO), olive oil (OO), sunflower oil (SFO), rice germ oil (RGO), walnut oil (WO), torreya seed oil (TSO), and grapeseed oil (GSO) were used to investigate the formation of heterocyclic amines (HAs) in roasted beef patties. Seven HAs, including 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4-dimethyl-3H-imidazo[4,5-f]quinolone (MeIQ), 2-amino-3-methyl-3H-imidazo[4,5-f]quinoxaline (IQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 1-methyl-9H-pyrido[3,4-b]indole (harman), and 9H-pyrido[3,4-b]indole (norharman) were detected in control patties and patties with vegetable oils. GSO, SFO, and WO greatly reduced the content of PhIP and MeIQ. 1.25%TSO and 3.75% RGO showed higher inhibition effects on the more strongly mutagenic compounds (PhIP, MeIQ, IQx, 4,8-DiMeIQx, MeIQx). SBO, PO, and RSO promoted imidazoquin(ox)aline (MeIQ, MeIQx, 4,8-DiMeIQx, and IQx) and β-carboline (harman and norharman); 1.25% SBO had the most significant promoting effect on total HA. This could be useful for the reduction of HA by selecting oils during cooking.

Bromopyrylium Derivatization Facilitates Identification by Mass Spectrometry Imaging of Monoamine Neurotransmitters and Small Molecule Neuroactive Compounds

Mass spectrometry imaging using matrix-assisted laser desorption/ionization and desorption electrospray ionization has recently been employed to investigate the distribution of neurotransmitters, including biogenic amines and amino acids, directly in brain tissue sections. Ionization is facilitated by charge-tagging through pyrylium derivatization of primary amine containing neurotransmitters directly in tissue sections, significantly improving the limit of detection. Since the derivatization adds carbon and hydrogen to the target compounds, the resulting isotopic patterns of the products are not distinctive from those of the nonderivatized species. Here, we describe an approach for chemically modifying the reactive pyrylium ion to introduce the distinct isotopic signature of bromine in mass spectra of chemically derivatized substances in tissue sections. The method enables monoamine compounds to be distinguished directly in tissue sections, facilitating their identification.

Determination of atmospheric amines at Seoul, South Korea via gas chromatography/tandem mass spectrometry

Due to their important roles in salt-producing acid-base reactions, new particle formation (NPF), and as precursors in secondary organic aerosol (SOA) producing reactions, the atmospheric concentrations of particulate volatile amines (dimethylamine (DMA), ethylamine, diethylamine (DEA), propylamine, and butylamine) at Seoul were analyzed and evaluated. To quantify the presence of volatile amines in particulate matter with aerodynamic diameters less than or equal to a nominal 2.5 μm (PM_2.5), an efficient and rapid analytical method based on in-matrix ethyl chloroformate (ECF) derivatization followed by headspace solid-phase microextraction (HS-SPME) was developed and validated using gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) in the multiple reaction monitoring (MRM) mode. The annual mean concentration of the total 5 target amines was 5.56±2.76 ng/m³ and the seasonal difference was small. The concentrations of particulate amines measured in this study were lower than those observed in Zongludak, Turkey, Nanjing, China, and Jeju, Korea but slightly higher than that reported in Kobe, Japan. The concentrations of the nitrosamines (nitrosodimethylamine (NDMA) and nitrosodiethylamine (NDEA)), and of the nitramines (dimethylnitramine (DMN) and diethylnitramine (DEN)) measured along with those of the target amines were used in a simple linear regression analysis. It indicates the contribution of DMA to the formation of NDMA in all seasons (except the fall) and DEA to the formation of NDEA in the summer, while DMA and DEA did not significantly contribute to the formation of nitramines.

Analysis of clozapine in its tablets using two novel spectrophotometric reactions targeting its tertiary amino group

Two simple spectrophotometric methodologies have been proposed and validated for the measurement of an atypical antipsychotic drug Clozapine (CLZ). Method A depends on interaction of CLZ with N-bromosuccinimide(NBS) resulting in formation of a yellowish orange colored product, measured at 320 nm. The linearity range was 5.0-70.0 μg/mL. Method B depends on condensation of the same drug with acetic acid mixed anhydride reagent producing a purple colored product, measured at 319 nm. The linearity range was 8.0-24.0 μg/mL. All parameters affecting the reaction condition (volume of both reagent, temperature, time and the different diluting solvents) were optimized. Both methods were successfully applied to assay CLZ in its pure form and tablets giving mean percentage recoveries of (98.87 ± 1.8 and 100 ± 1.7) for method A, and corresponding values of (98.6 ± 0.96 and 99.5 ± 1) for method B. Besides, the study of reactions stoichiometry was performed and the reaction mechanisms were proposed.

Towards a generic method for ion chromatography/mass spectrometry of low-molecular-weight amines in pharmaceutical drug discovery and development

RATIONALE

Low-molecular-weight amines are encountered in pharmaceutical analysis, e.g. as reactants in chemical syntheses, but are challenging to analyse using ultrahigh-performance liquid chromatography/mass spectrometry (UHPLC/MS) due to their high polarity causing poor retention. Ion chromatography/mass spectrometry (IC/MS) is an emerging technique for polar molecule analysis that offers better separation. A generic IC/MS method would overcome problems associated with using UHPLC/MS in drug discovery and development environments.

METHODS

Amine standards were analysed using IC/MS with gradient elution (variety of column temperatures evaluated). An electrospray ionisation (ESI) quadrupole mass spectrometer was operated in positive ion polarity in scanning mode. The make-up flow composition was evaluated by assessing the performance of a range of organic modifiers (acetonitrile, ethanol, methanol) and additives (acetic acid, formic acid, methanesulfonic acid). The ESI conditions were optimised to minimise adduct formation and promote generation of protonated molecules.

RESULTS

The performance attributes were investigated and optimised for low-molecular-weight amine analysis. Organic solvents and acidic additives were evaluated as make-up flow components to promote ESI, with 0.05% acetic acid in ethanol optimal for producing protonated molecules. The hydrogen bonding capability of amines led to abundant protonated molecule-solvent complexes; optimisation of source conditions reduced these, with collision-induced dissociation voltage having a strong effect. The detection limit was ≤1.78 ng for the amines analysed, which is fit-for-purpose for an open-access chemistry environment.

CONCLUSIONS

This study demonstrates the value of IC/MS for analysing low-molecular-weight amines. Good chromatographic separation of mixtures was possible without derivatisation. Ionisation efficiency was greatest using a make-up flow of 0.05% acetic acid in ethanol, and optimisation of ESI source conditions promoted protonated molecule generation for easy determination of molecular weight.

Meat intake, meat cooking methods, and meat-derived mutagen exposure and risk of sessile serrated lesions

BACKGROUND

Red and processed meat, recognized carcinogens, are risk factors for colorectal neoplasia, including polyps, the precursor for colorectal cancer. The mechanism is unclear. One possible explanation is the mutagenic activity of these foods, perhaps due to generation during cooking [e.g., heterocyclic amine (HCA) intake]. Few studies have evaluated meat intake and sessile serrated lesion (SSL) risk, a recently recognized precursor, and no study has evaluated meat cooking methods and meat-derived mutagens with SSL risk.

OBJECTIVE

We evaluated intakes of meat, meat cooking methods, and inferred meat mutagens with SSL risk and in comparison to risk of other polyps.

METHODS

Meat, well-done meat, and inferred meat mutagen intakes were evaluated. Polytomous logistic regression models were used to estimate ORs and 95% CIs among cases (556 hyperplastic polyp, 1753 adenoma, and 208 SSL) and controls (3804) in the large colonoscopy-based, case-control study, the Tennessee Colorectal Polyp Study.

RESULTS

The highest quartile intakes of red meat (OR: 2.38; 95% CI: 1.44, 3.93), processed meat (OR: 2.03; 95% CI: 1.30, 3.17), well-done red meat (OR: 2.19; 95% CI: 1.34, 3.60), and the HCA 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQX; OR: 2.48; 95% CI: 1.49, 4.16) were associated with increased risk of SSLs in comparison to the lowest quartile intake.

CONCLUSIONS

High intakes of red and processed meats are strongly and especially associated with SSL risk and part of the association may be due to HCA intake. Future studies should evaluate other mechanism(s) and the potential for primary prevention.

Integrated fate assessment of aromatic amines in aerobic sewage treatment plants

The fate and exposure of chemicals in sewage treatment plants (STPs) are major considerations in risk assessment and environmental regulation. The biodegradability and removal of seven aromatic amines were systematically evaluated using a three-tiered integrated method: a standard ready biodegradability test, an aerobic sewage treatment simulation method, and model prediction. In tier 1, the seven aromatic amines were not readily biodegraded after 28 days. In adapted aerobic active sludge, 4-isopropyl aniline, 2,4-diaminotoluene, and 4-nitroaniline among them exhibited the degradation half-life time less than 20 h, the other four aromatic amines exhibited persistent with degradation half-life of > 60 h. In tier 2 of the aerobic sewage treatment simulation testing, 2,4-diaminotoluene, 4-nitroaniline, and 4-isopropylaniline demonstrated moderately to high overall removal. Hydraulic retention time (HRT) affects the removal with the optimum HRT was determined to be 12 h to 24. 2,6-Dimethyl aniline, 2-chloro-4-nitroaniline, 2,6-diethylaniline, and 3,4-dichloroaniline were not removed during the test, indicting these four aromatic amines will enter surface water and hence pose a potential risk to aquatic ecology. Considering the lack of an STP model in China for regulation purposes, in tier 3, we developed a Chinese STP (aerobic) (abbreviated as C-STP(O)) model that reflects a universal scenario for China to predict the fate. The predicted degradation, volatilization, and absorption showed a close relationship to the physicochemical properties of the chemicals, and had same tendency with tier 2 simulation test. The prediction showed that biodegradation rather than absorption or volatilization was the main removal process of aromatic amines in aerobic STP. With the combination of modified kinetics test with C-STP (O) model, the chemical fate can be more accurately predicted than using only the readily biodegradation result.

Cellulose-based fluorescent sensor for visual and versatile detection of amines and anions

It is practical and challenging to construct ultrasensitive and multi-responsive sensors for visual and real-time monitoring of the environment. Herein, a cellulose-based multi-responsive fluorescent sensor (Phen-MDI-CA) is fabricated, and realizes a visual and ultrasensitive detection of not only various amines but also three anions based on the change of the fluorescence and/or visible colors. Once exposure to various amines in both the solution and vapor state, the Phen-MDI-CA solution and test paper exhibit different fluorescence colors, which can be used to distinguish triethylamine, ethylenediamine, methylamine, aniline, hydrazine and pyrrolidine from other amines. Moreover, via combining the Phen-MDI-CA with the Phen-MDI-CA/malachite green ratiometric system, phosphate (PO₄^3-), carbonate (CO₃^2-) and borate (B₄O₇^2-) can be visually and accurately recognized depending on the change of the visible and fluorescence colors. In fluorescent mode, the LOD for B₄O₇^2-, PO₄^3- and CO₃^2- ions is as low as 0.18 nmol, 0.69 nmol and 0.86 nmol, respectively. Significantly, the Phen-MDI-CA can readily make a qualitative and quantitative detection of B₄O₇^2-, PO₄^3- and CO₃^2- anions in the mixture of anions. The state-of-the-art responsive behavior of Phen-MDI-CA originates from the amplification effect of cellulose polymer chain and the differentiated interactions between the sensor and analytes.

Heterocyclic Amine Formation in Grilled Chicken Depending on Body Parts and Treatment Conditions

Heterocyclic amines (HCAs) carcinogenicity is known since the 1970′s, but the exact way of their formation is still unclear. During these examinations different body parts (breast filet with and without skin, thigh filet without skin and full wing with skin) of chickens from the same Ross 308 strain were analyzed after grilling with the combination of 3-3 temperature and duration levels (150-180-210 °C and 2.5-5-10 min per side). Five different kinds of heterocyclic amines (HAR, NOR, MeIQx, 4,8-DiMeIQx and PhIP) were detected by HLPC-MS/MS. The results obtained from the present study confirm that, in general, the higher the temperature and longer the duration of the grilling the more HCAs will be generated. Grilling of chicken thigh without bones and skin resulted in lower amounts of HCAs generated in comparison to the grilling of chicken breast without skin. The presence of skin on the chicken breast increased the amounts of HCAs formed, especially if grilling was performed at high temperature for longer duration, especially at 210 °C for 10 min. In case of grilling the chicken wings, the amounts of HCAs formed were lower than observed in the breast.

[Determination of seven heterocyclic aromatic amines in oils and fried foods by ultra performance liquid chromatography-triple quadrupole mass spectrometry]

An ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS) method was developed for the determination of seven heterocyclic aromatic amines (HCAs) in oil and fried food samples. The samples were extracted with acetonitrile containing 1% (v/v) ammonia water, defatted by n-hexane saturated with acetonitrile, and cleaned up with PCX solid phase extraction column. The extracts were separated on a Waters ACQUITY UPLC BEH C18 reversed-phase column (50 mm×2.1 mm, 1.7 μm) with gradient elution by using acetonitrile-10 mmol/L ammonium formate aqueous solution as the mobile phase. Quantitative detection was performed by using a positive-ion electrospray ionization source in the multiple reaction monitoring (MRM) mode, employing an internal isotope standard. The method showed good linear relationships in the range of 0.5-100 μg/L for the seven HCAs with correlation coefficients (R²)>0.999. The average recoveries ranged from 64.31% to 113.8% with the relative standard deviations of 0.18%-9.26% at the three spiked levels in oil and fried food samples. The limits of detection (LODs) and limits of quantification (LOQs) were 0.01-0.14 ng/g and 0.09-0.38 ng/g, respectively. The method is sensitive, accurate, and suitable for the determination and confirmation of the seven HCAs in oil and fried food samples.

Effects of smoke flavoring using different wood chips and barbecuing on the formation of polycyclic aromatic hydrocarbons and heterocyclic aromatic amines in salmon fillets

Herein, the concentrations of food toxicants, polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HAAs), in salmon fillets smoke flavored with different smoking wood chips (oak, apple, bourbon soaked oak, cherry and hickory) and barbecuing were determined. Benzo[a]anthracene (up to 0.24 ng/g) and chrysene (0.22 ng/g) were determined in the raw salmon fillets. While ∑PAH8 (benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, indeno[1,2,3-cd]pyrene) in the raw samples ranged between 0.44 and 0.46 ng/g, smoke flavoring increased the amount of ∑PAH8 and the amount varied between 0.47 and 0.73 ng/g. Salmon smoked flavored with bourbon soaked oak, cherry and hickory wood chips and barbecued showed significantly (P <0.05) lower contents of ∑PAH4 (benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[a]pyrene) and ∑PAH8 compared to non-smoke flavored barbecued samples. Additionally, smoke flavoring with apple, bourbon soaked oak, and cherry wood chips significantly (P <0.05) reduced the total HAA contents in barbecued salmon. A remarkable result was that the bourbon-soaked oak and cherry wood chips had inhibitory effects on both PAH and HAA contents. In sum, barbecued non-smoke flavored and smoke flavored salmon with different wood chips could be considered safe from the perspective of the detected amounts of PAHs and HAAs in salmon fillets.

Reaction-Based Amine and Alcohol Gases Detection with Triazine Ionic Liquid Materials

We demonstrated in this work the use of affinity ionic liquids, AIL 1 and AIL 2, for chemoselective detection of amine and alcohol gases on a quartz crystal microbalance (QCM). These detections of gaseous amines and alcohols were achieved by nucleophilic aromatic substitution reactions with the electrophilic 1,3,5-triazine-based AIL 1 thin-coated on quartz chips. Starting with inexpensive reagents, bicyclic imidazolium ionic liquids AIL 1 and AIL 2 were readily synthesized in six and four synthetic steps with high isolated yields: 51% and 63%, respectively. The QCM platform developed in this work is readily applicable and highly sensitive to low molecular weight amine gases: for isobutylamine gas (a bacterial volatile) at 10 Hz decrease in resonance frequency (i.e., ΔF = -10 Hz), the detectability using AIL 1 was 6.3 ppb. Our preliminary investigation on detection of the much less nucleophilic alcohol gas by AIL 1 was also promising. To our knowledge, no example to date of reports based on nucleophilic aromatic substitution reactions demonstrating sensitive gas detection in these triazine ionic liquids on a QCM has been reported.

Amphiphilic calix[4]arenes as a highly selective gas chromatographic stationary phase for aromatic amine isomers

Efficient separation of aromatic amine isomers is a challenging issue in chemical industry and environmental analysis. Here we report the use of p-amino-tetradecyloxy-calix[4]arene (C4A-NH₂) as a novel stationary phase for gas chromatographic (GC) separations. The statically coated C4A-NH₂ capillary column showed a high column efficiency of 4332 plates/m for a 0.25 mm ID column and medium polarity. The C4A-NH₂ stationary phase exhibited an excellent separation performance both for aromatic amine isomers and a complex mixture of aliphatic analytes with a wide ranging polarity, showing distinct advantages over the commercial polysiloxane stationary phases via diversified molecular interactions covering H-bonding, π-π, van der Waals interactions and shape-fitting selectivity. The retention mechanisms of aromatic amine isomers on C4A-NH₂ column were further investigated by quantum chemistry calculations. In addition, the C4A-NH₂ column showed good column repeatability with relative standard deviation (RSD) values of 0.03%-0.07% for run-to-run, 0.10%-0.27% for day-to-day and 2.6%-5.7% for column-to-column, respectively, and thermal stability up to 240℃.

Odor assessment of NH3 and volatile sulfide compounds in a full-scale municipal sludge aerobic composting plant

Methods for assessing odors in municipal sewage sludge aerobic composting plants (MSSACPs) have been ineffective. This study identified the emission amount of typical odor-producing compounds, including NH₃ and volatile sulfide compounds from a full-scale MSSACP, and evaluated risks of odor emissions based on odor intensity and odor active value. Results revealed all sampling sites (i.e. sludge stacking yard, composting workshop, and screening workshop) produced serious odors, especially in the composting workshop. In the composting workshop, the amounts of DMDS (174.59 μg·dry kg^-1) and DMS (71.64 μg·dry kg^-1) emitted were far lower than that of NH₃ (6062.56 μg·dry kg^-1). However, DMDS and DMS showed a similar intensity as NH₃ according to odor intensity assessment. Furthermore, both of their odor active values were higher than that of NH₃. Using results from both odor intensity and odor active value were more reliable for the assessment of odors from MSSACPs.

The effect of using different types and rates of onion-water extract in meatball production on the formation of heterocyclic aromatic amines

BACKGROUND

The effect of using different types (yellow, white and purple) and rates (0.25%, 0.50% and 0.75%) of onion-water extract in meatball production on the various quality criteria of meatballs and the formation of heterocyclic aromatic amines (HCAs) was investigated.

RESULTS

It was determined that cooking process caused a reduction in the water content of meatballs as well as an increase in pH values. MeIQx, 7,8-DiMeIQx, 4,8-DiMeIQx, PhIP, AαC and MeAαC could not be detected in any of the analyzed meatballs, while IQx, IQ and MeIQ were determined in some of the samples.

CONCLUSION

The use of 0.25% and 0.50% white onion-water extract in meatball preparation inhibited the formation of IQx and IQ that were identified in the control group, but their quantities could not be determined. However, the use of water extract of varying types of onions in meatball preparation increased the total HCA content due to the increase of the MeIQ formation. In addition, it was determined that as the rate of onion-water extract for varying types of onions increased, the total HCA amount also increased. The total HCA amount of the meatballs varied between 0.05 and 0.1 ng g^-1 . © 2019 Society of Chemical Industry.

Analysis of heterocyclic amines in meat products by liquid chromatography – Tandem mass spectrometry

Heterocyclic amines (HCAs), a class made up of more than 25 compounds, are unintended hazardous substances that are generated by the heating or processing of proteinaceous foods at high temperatures. The International Agency for Research on Cancer (IARC) has classified four such HCAs (IQ, MeIQ, MeIQx, and PhIP) as being probable or possible human carcinogens. In this study, two sample preparation strategies, liquid–liquid extraction (LLE) with solid-phase extraction (SPE) and a rapid, easy, cheap, effective, rugged, and safe extraction (QuEChERS) method, were investigated for the determination of 11 types of HCAs in meat products by LC-MS/MS. The HCAs in the samples were first extracted with acetonitrile by LLE, and followed by SPE. In the case of QuEChERS extraction, acetonitrile is used as the LLME solvent, and PSA, C18EC and MgSO₄ were used as the dSPE sorbent. Both methods showed good performance with respect to precision (RSD < 15.15%), accuracy (79.80–117.64%), recovery (52.39–116.88%), limit of quantitation for a spiked meat extract (0.01–10 ppb) and correlation coefficients (>0.993). The QuEChERS extraction strategy provided a better linear dynamic range and superior sensitivity in comparison with the LLE-SPE approach. HCAs were successfully quantified in real samples using the two proposed approaches by LC-MS/MS.

Direct and indirect electrochemical oxidation of amine-containing pharmaceuticals using graphite electrodes

This study investigated the direct and indirect electro-oxidation of amine-containing pharmaceuticals (acetaminophen (ACT), diclofenac (DIC), and sulfamethoxazole (SMX)) by using graphite electrodes, and to compare the influence by using different electrolytes (Na₂SO₄ and NaCl). Under the optimum conditions of current (I) at 0.5 A, in direct system, 74.3%, 90.0%, 81.6% of ACT, DIC, and SMX were respectively removed after 60 min (k = 0.023, 0.037, 0.027 min^-1), 48.9%, 85.9%, 68.2% of TOC respectively removed after reaction time. In contrast, at the same current intensity, in indirect system, ACT, DIC, and SMX were eliminated within 30 min (k = 0.117, 0.307, 0.170 min^-1), 89.6%, 92.6%, 99.6% of TOC respectively removed after reaction time. The results indicated that the dissociated compounds were attracted to the anode due to electrostatic forces and had higher mass transformation rates in the direct electro-oxidation process. According to the cyclic voltammogram, indirect oxidation occurred when active chlorine species were generated from chloride ions anodically to destroy pollutants. Based on intermediates detected during electro-oxidation treatment by ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), only oxidized intermediates were found in the direct oxidation system, while both oxidized and chlorinated intermediates were found in the indirect oxidation system.

Amino-Functionalized Al-MOF for Fluorescent Detection of Tetracyclines in Milk

A fluorescent method for detection of tetracyclines (TCs) in milk was developed by using the NH₂-MIL-53(Al) nanosensor synthesized via a one-pot hydrothermal method. The nanosensor had a crystalline nanoplates structure with rich groups of -NH₂ and -COOH. The -NH₂/-COOH of NH₂-MIL-53(Al) reacted with the -CO-/-OH of TCs to form a complex. The electron of -NH₂/-COOH from the NH₂-BDC ligand transferred to the -CO-/-OH of TCs. -NH₂ of the NH₂-MIL-53(Al) interacted with the -CO-/-OH of TCs by hydrogen bonding. The quenching efficiency of the inner filter effect (IFE) was calculated to contribute 57-89%. The synergistic effect of photoinduced electron transfer (PET) and IFE account for fluorescence quenching. TCs were quantitatively detected in milk samples with recoveries of 85.15-112.13%; the results were in great accordance with high-performance liquid chromatography (HPLC) ( P > 0.05), confirming the NH₂-MIL-53(Al) nanosensor has potential applicability for the detection of TCs in food matrix.