Desorption Electrospray Ionization Tandem Mass Spectrometry for Detection of 24 Carcinogenic Aromatic Amines in Textiles

A new organic soluble cucurbit[7]uril-truxene derivative as stationary phase for gas chromatographic separation of some challenging isomers

The insolubility of parent cucurbit[n]uril or substituted-cucurbit[n]uril derivatives in organic solvents has always been a key factor restricting the column efficiency and selectivity of capillary gas chromatography column based on cucurbit[n]uril. In this work, a novel organic soluble cucurbit [7]uril-truxene derivative (Q [7]-Tr) was synthesized by Heck coupling reaction between the mono-iodinated hexahexyl-truxene and 4-vinylbenzyloxy-Q [7]. A capillary gas chromatographic column was prepared by static method with this derivative as stationary phase. The column exhibited moderate polarity and an efficiency of 5857 plates/m using n-dodecane as analyte at 120 °C, indicating the highest column efficiency of all the based-cucurbit[n]uril columns published. The Q [7]-Tr column showed high resolutions for a wide range of analytes with different polarities and better separated selectivity towards tough isomers such as aromatic amines isomers and xylene isomers compared to commercial HP-5, DB-35, Stabilwax and Q [7]-based columns. Moreover, the new column exhibited high thermal stability up to 320 °C and excellent repeatability, demonstrating a great potential as a new stationary phase in capillary gas chromatography.

The first balloon-borne sample analysis of atmospheric carbonaceous components reveals new insights into formation processes

Atmospheric aerosol optical, physical, and chemical properties play a fundamental role in the Earth's climate system. A better understanding of the processes involved in their formation, evolution, and interaction with radiation and the water cycle is critical. We report the analysis of atmospheric molecules/particles collected with a new sampling system that flew under regular weather balloons for the first time. The flight took place on January 18, 2022 from Reims (France). The samples were subsequently analyzed by high-resolution mass spectrometry (Orbitrap) to specifically infer hundreds of organic components present in 4 different layers from the troposphere to the stratosphere (up to 20 km). Additional measurements of O₃, CO, and aerosol concentrations a few hours before this flight took place to contextualize the sampling. After separating common species found on each filter that might be common to atmospheric layers or residuals for contaminations, we found that each sample yields significant differences in the number and size of organic species detected that should reflect the unique composition of atmospheric layers. While tropospheric samples yield significantly oxidized and saturated components, with carbon numbers below 30 that might be explained by complex organics chemistry from local and distant source emissions, the upper tropospheric and stratospheric samples were associated with increased carbon numbers (C > 30), with a significantly reduced unsaturation number for the stratosphere, that might be induced by strong UV radiations. The multimodal distributions of carbon numbers in chemical formulas observed between 15 and 20 km suggest that oligomerization and growth of organic molecules may take place in aged air masses of tropical origin that are known to carry organic compounds even several km above the tropopause where their lifetime significantly increases. In addition, the presence of organics may also reflect the extended influence of wildfires smoke injected during the spring and summer in the NH hemisphere before the in situ observations and their long-lifetime in the upper troposphere and stratosphere.

Development and Application of Desorption Electrospray Ionization Mass Spectrometry for Historical Dye Analysis

A desorption electrospray ionization (DESI) source was built and attached to a Bruker 7T SolariX FT-ICR-MS for the in situ analysis of 14 early synthetic dyestuffs. Optimization using silk and wool cloths dyed with rhodamine B concluded that when using a commercial electrospray emitter (part number: 0601815, Bruker Daltonik), a nebulizing gas (N₂) pressure of 3.9 bar and a sprayer voltage of 4.5 kV (positive ionization mode) or 4.2 kV (negative ionization mode), a solvent system of 3:1 v/v ACN:H₂O, and a sprayer incident angle, α, of 35° gave the highest signal-to-noise ratios on both silk and wool for the samples investigated. The system was applied to modern early synthetic dye references on silk and wool as well as historical samples from the 1893 edition of Adolf Lehne's Tabellarische Übersicht über die künstliche organischen Farbstoffe und ihre Anwendung in Färberei und Zeugdruck [Tabular overview of the synthetic organic dyestuffs and their use in dyeing and printing]. The successful analysis of six chemically different dye families in both negative and positive modes showed the presence of known degradation products and byproducts arising from the original synthetic processes in the historical samples. This study demonstrates the applicability and potential of DESI-MS to the field of historical dye analysis.

Profiles of primary aromatic amines, nicotine, and cotinine in indoor dust and associated human exposure in China

Despite the widespread use of primary aromatic amines (AAs) in consumer products, little is known about their prevalence in house dust. In this study, we investigated the occurrence of 35 AAs and two tobacco chemical markers (nicotine and its breakdown product cotinine) in 119 samples of house dust collected from five provinces in China. Ten of the 35 AAs and [nicotine and cotinine] were found in >80% and 100% of the samples, respectively, at concentration ranges of 29.1-19,200 (median: 700 ng/g) and 23.2-22,400 (4600) ng/g, respectively. Aniline was the predominant AA found in all dust samples (median: 257 ng/g). Dust samples from Henan and Shanxi provinces contained higher summed concentrations of the 10 AAs than those from Sichuan and Shandong, although the concentrations did not vary significantly among the five provinces (p > 0.05). A significant (p = 0.048), positive correlation (r = 0.882) existed between concentrations of nicotine and cotinine in dust samples. Similarly, concentrations of AAs were significantly correlated with those of nicotine in dust samples. Dyestuffs, rubber products, polyurethane foam and tobacco smoke are the major sources of AAs in the indoor environment. The estimated daily intakes (EDI) through dust ingestion ranged from 0.349 (adults) to 6.62 ng/kg-bw/day (toddlers) for AAs and from 1.27 to 51.1 ng/kg-bw/day for nicotine which are well below the current tolerable daily intakes.

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.

Photocatalytic reduction-based liquid microjunction surface sampling-mass spectrometry for rapid in situ analysis of aromatic amines originating from azo dyes in packaging papers

A rapid in situ analytical method was developed for the detection of generated carcinogenic aromatic amines from banned azo dyes utilizing a photocatalytic reduction-based liquid microjunction surface sampling (LMJSS)-mass spectrometry (MS) system. We utilized photocatalytic reduction under UV irradiation with TiO₂ as catalyst to have rapid and mild reduction of azo dyes. The reaction conditions were optimized to have complete photocatalytic reduction within 2-5 min in pure methanol at room temperature. TiO₂ was immobilized in the inner wall of the capillaries in the LMJSS system to achieve in situ sampling-online rapid reduction-MS detection for aromatic amines originating from azo dyes in packaging surface. The yields of in-tube photocatalytic reduction were near 100% by delivering the azo dye extracts through the capillary at 1 μL/min under UV irradiation. With this design, in situ analysis was completed within 2 min via direct MS detection and 7 min via liquid chromatography (LC)-MS detection. The detection limits for five aromatic amines originating from four different azo dyes were in the range of 1-17 mg/kg with relative standard deviations (RSDs) < 8.5%. In the application of the new method, four carcinogenic aromatic amines were detected and identified in three commercial packaging materials, and the quantitation results were comparable with those obtained by the conventional chemical reduction-LC-MS method (relative recovery, 81-121%). Moreover, due to the spatial resolution of the present method with a flow probe, MS imaging was achieved demonstrating clear azo dye patterns of a lab-made sample.

Green preparation of carbon dots from Momordica charantia L. for rapid and effective sensing of p-aminoazobenzene in environmental samples

p-Aminoazobenzene (pAAB) is a hazardous azo dye that causes considerable harm to human health and the environment. The development of novel and sensitive sensors for the rapid detection of pAAB is in high demand. In this study, a simple fluorescent sensor for pAAB detection is designed based on carbon dots (CDs) which are prepared using green carbon source of Momordica charantia L. via a facile hydrothermal approach. The fluorescence spectra of CDs exhibit considerable overlap with the absorption band of pAAB, and the fluorescence is specifically suppressed in the presence of pAAB ascribed to the inner filter effect. Good and wide linearity is observed in the pAAB concentration range of 0.01-12.5 μg mL^-1 with a lower detection limit of 3.9 ng mL^-1. The established method achieves good results with a rapid analysis of pAAB in different practical water and soil samples. The as-constructed fluorescent sensor provides a simple, rapid, economical and eco-friendly platform and possesses prospective applications for the effective, selective and sensitive detection of pAAB in the environmental field.

Exploration of an odorous aldehydes and ketones produced by Uroglena americana using high resolution mass spectrometry, GC-Olfactometry, and multivariate analysis

Off-flavor events in tap water have been reported from various regions of Japan. Fishy smell is the second most common off-flavor in Japan and Uroglena americana (U. americana) is known to be a major contributor to the smell. However, the causative compound of the smell it produces still remains unrevealed to the best of our knowledge. In this study, an exploration of odorous aldehydes and ketones originating from U. americana was performed with a view to discovering a possible candidate substance of causative compounds. Environmental samples containing U. americana colony and cultured media with U. americana were analyzed with two high resolution mass spectrometers, one of them is coupled with liquid chromatography (LC-HRMS), and the other is with gas chromatography and a sniffing port (GC-O-HRMS). Multivariate analyses (MVA) were utilized to explore a compound that is likely to be odorous aldehydes or ketones with a reduced time of exploration. A combination of LC-HRMS and MVA resulted in the selection of one candidate substance and its formula was determined to be C₁₃H₂₀O₃ on the basis of its accurate mass and natural isotopic pattern. The candidate substance underwent GC-O-HRMS analyses and milk-like smell was detected at around its retention time. Although the detected smell was different from fishy smell, it is expected that the fishy smell is caused by multiple compounds to which the candidate substance belongs. First generation product ion spectra of the candidate substance suggested that it contains a hydroxyl group, a cyclohexene ring, and a ketone moiety.

Amphiphilic Block Copolymer PCL-PEG-PCL as Stationary Phase for Capillary Gas Chromatographic Separations

This work presents the first example of utilization of amphiphilic block copolymer PCL-PEG-PCL as a stationary phase for capillary gas chromatographic (GC) separations. The PCL-PEG-PCL capillary column fabricated by static coating provides a high column efficiency of 3951 plates/m for n-dodecane at 120 °C. McReynolds constants and Abraham system constants were also determined in order to evaluate the polarity and possible molecular interactions of the PCL-PEG-PCL stationary phase. Its selectivity and resolving capability were investigated by using a complex mixture covering analytes of diverse types and positional, structural, and cis-/trans-isomers. Impressively, it exhibits high resolution performance for aliphatic and aromatic isomers with diverse polarity, including those critical isomers such as butanol, dichlorobenzene, dimethylnaphthalene, xylenol, dichlorobenzaldehyde, and toluidine. Moreover, it was applied for the determination of isomer impurities in real samples, suggesting its potential for practical use. The superior separation performance demonstrates the potential of PCL-PEG-PCL and related block copolymers as stationary phases in GC and other separation technologies.

Novel approach for the rapid screening of banned aromatic amines in dyed textiles using a chromogenic method

A novel and simple method utilizing a chromogenic reaction on filter paper is introduced for the rapid screening of banned aromatic amines released from azo dyes. The proposed method involves the sample preparation protocols outlined by the current standard method and the chromogenic reaction of extracted aromatic amines on filter paper. Based on the principle of the reaction between primary amines and aldehydes, p-dimethylaminobenzaldehyde (DMAB) was used as the chromogenic reagent for the rapid screening of 24 carcinogenic aromatic amines and aniline without any chromatographic instruments under optimized experimental conditions. The detection limit for all the aromatic amines in this study was less than 15 mg/kg. A total of 727 dyed textile samples were analyzed using both the present standard method and the proposed method simultaneously. Using the proposed method, a total of 471 samples did not require further instrumental analysis, which can dramatically save instrumental detection time (61.2%), can decrease instrumental detection costs, and can avoid the use of large amounts of toxic reagents. The proposed method has been applied to detect banned aromatic amines in some inspection institutions and dye factories and has large social and economic benefits. Graphical abstract Chromogenic reaction methods.

MALDI imaging of enzymatic degradation of glycerides by lipase on textile surface

Most modern laundry detergents contain enzymes such as proteases, amylases, and lipases for more efficient removal of stains containing proteins, carbohydrates, and lipids during wash at low temperature. The function of the lipases is to hydrolyse the hydrophobic triglycerides from fats and oils to the more hydrophilic lipids diglycerides, monoglycerides and free fatty acids. Here, we use MALDI imaging to study the effect of enzymatic degradation of triglycerides by lipases directly on the textile surface. Textile samples were created by using swatches of different textile blends, adding a lipid stain and simulating washing cycles using well-defined detergents with lipase concentrations ranging between 0 and 0.5ppm. After washing, the textile swatches as well as cryo-sections of the swatches were imaged using MALDI imaging in positive ion mode at pixel sizes of 15-75μm. Similar samples were imaged by DESI-MSI for comparison. Despite the rough surface and non-conductive nature of textile, MALDI imaging of glycerides on textile was readily possible. The results show extensive enzymatic degradation of triglycerides into diglycerides, and images suggest that this degradation takes place in a quite heterogeneous manner as also observed in images of cross-sections. DESI-imaging reveals the same kind of enzymatic degradation, but with a more homogeneous appearance. While the enzymatic degradation is exemplified in a few images, the overall degradations process was monitored by extraction of ion intensities from 298 individual ion masses of mono-, di- and triglycerides and free fatty acids. MALDI imaging of glycerides was possible directly from a textile surface, allowing visualization of the enzymatic degradation of fatty stains on textile during the laundry process. The images showed an inhomogeneous presence of diglycerides after lipase treatment both in planar images of the textile surface as well as in cross-sections suggesting a non-uniform enzyme effect or extraction of the lipase reaction products from the textile.

Microwave induced plasma desorption ionization (MIPDI) mass spectrometry for qualitative and quantitative analysis of preservatives in cosmetics

The quantitative and qualitative behaviors of the MIPDI source were systematically studied for the first time in this work.

Sensitive ionization of non-volatile analytes using protein solutions as spray liquid in desorption electrospray ionization mass spectrometry

RATIONALE

Desorption electrospray ionization (DESI) is the most popular ambient ionization technique for direct analysis of complex samples without sample pretreatment. However, for many applications, especially for trace analysis, it is of interest to improve the sensitivity of DESI-mass spectrometry (MS).

METHODS

In traditional DESI-MS, a mixture of methanol/water/acetic acid is usually used to generate the primary ions. In this article, dilute protein solutions were electrosprayed in the DESI method to create multiply charged primary ions for the desorption ionization of trace analytes on various surfaces (e.g., filter paper, glass, Al-foil) without any sample pretreatment. The analyte ions were then detected and structurally characterized using a LTQ XL mass spectrometer.

RESULTS

Compared with the methanol/water/acetic acid (49:49:2, v/v/v) solution, protein solutions significantly increased the signal levels of non-volatile compounds such as benzoic acid, TNT, o-toluidine, peptide and insulin in either positive or negative ion detection mode. For all the analytes tested, the limits of detection (LODs) were reduced to about half of the original values which were obtained using traditional DESI. The results showed that the signal enhancement is highly correlated with the molecular weight of the proteins and the selected solid surfaces.

CONCLUSIONS

The proposed DESI method is a universal strategy for rapid and sensitive detection of trace amounts of strongly bound and/or non-volatile analytes, including explosives, peptides, and proteins. The results indicate that the sensitivity of DESI can be further improved by selecting larger proteins and appropriate solid surfaces.

Sinapine detection in radish taproot using surface desorption atmospheric pressure chemical ionization mass spectrometry

Plant research and natural product detection are of sustainable interests. Benefited by direct detection with no sample preparation, sinapine, a bioactive chemical usually found in various seeds of Brassica plants, has been unambiguously detected in radish taproot (Raphanus sativus) tissue using a liquid-assisted surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS). A methanol aqueous solution (1:1) was nebulized by a nitrogen sheath gas toward the corona discharge, resulting in charged ambient small droplets, which affected the radish tissue for desorption/ionization of analytes on the tissue surface. Thus, sinapine was directly detected and identified by tandem DAPCI-MS experiments without sample pretreatment. The typical relative standard deviation (RSD) of this method for sinapine detection was 5-8% for six measurements (S/N=3). The dynamic response range was 10(-12)-10(-7) g/cm2 for sinapine on the radish skin surface. The discovery of sinapine in radish taproot was validated by using HPLC-UV methods. The data demonstrated that DAPCI assisted by solvent enhanced the overall efficiency of the desorption/ionization process, enabling sensitive detection of bioactive compounds in plant tissue.

Differentiation of human kidney stones induced by melamine and uric acid using surface desorption atmospheric pressure chemical ionization mass spectrometry

Clinically obtained human kidney stones of different pathogenesis were dissolved in acetic acid/methanol solutions and then rapidly analyzed by surface desorption atmospheric pressure chemical ionization mass spectrometry (SDAPCI-MS) without any desalination treatment. The mass spectral fingerprints of six groups of kidney stone samples were rapidly recorded in the mass range of m/z 50-400. A set of ten melamine-induced kidney stone samples and nine uric acid derived kidney stone samples were successfully differentiated from other groups by principal component analysis of SDAPCI-MS fingerprints upon positive-ion detection mode. In contrast, the mass spectra recorded using negative-ion detection mode did not give enough information to differentiate those stone samples. The results showed that in addition to the melamine, the chemical compounds enwrapped in the melamine-induced kidney stone samples differed from other kidney stone samples, providing useful hints for studying on the formation mechanisms of melamine-induced kidney stones. This study also provides useful information on establishing a MS-based platform for rapid analysis of the melamine-induced human kidney stones at molecular levels.

Ambient ionization mass spectrometry: current understanding of mechanistic theory; analytical performance and application areas

Ambient ionization mass spectrometry allows the rapid analysis of samples or objects in their native state in the open environment with no prior preparation. Over the past six years, the ability of these techniques to provide selective analyte desorption and ionization, in combination with mass spectrometry (MS), has provided a growing number of powerful analytical alternatives across broad application areas, both quantitative and qualitative in nature, including pharmaceutical analysis, process chemistry, biological imaging, in vivo analysis, proteomics, metabolomics, forensics, and explosives detection. With the emergence of new ambient ionization methods, and the complementary nature of existing desorption and/or ionization techniques, additional hyphenated methods have been devised, which pushes the total number of documented methods to almost thirty. To cover all current ambient ionization techniques in detail would be too complex and detract from the main objective of this review. Rather, an overview of the field of ambient ionization MS will be given, followed by broad classification to allow detailed discussion of theory and common mechanistic factors underpinning a number of key techniques. Consideration will be given to experimental design, ease of implementation and analytical performance, detailing subsequent impact on a number of application areas, both established and emerging.

Ambient ionization mass spectrometry

Mass spectrometric ionization methods that operate under ambient conditions and require minimal or no sample pretreatment have attracted much attention in such fields as biomedicine, food safety, antiterrorism, pharmaceuticals, and environmental pollution. These technologies usually involve separate ionization and sample-introduction events, allowing independent control over each set of conditions. Ionization is typically performed under ambient conditions through use of existing electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) techniques. Rapid analyses of gas, liquid, and solid samples are possible with the adoption of various sample-introduction methods. This review sorts different ambient ionization techniques into two main subcategories, primarily on the basis of the ionization processes, that are further differentiated in terms of the approach used for sampling.