Integration of iron-manganese layered double hydroxide/tungsten carbide composite: An electrochemical tool for diphenylamine H•+ analysis in environmental samples.

Incompetent governance of post-harvest horticultural crops especially apples and pears lead to numerous physiological storage disorders. In order to manage this issue, diphenylamine (DPA) is widely used as an antioxidant and anti-scald agent to preserve fruits from superficial scalds and degradation during storage. As a result, this research focuses on utilizing disposable electrodes constructed with sphere-shaped iron-manganese layered double hydroxide (FeMn-LDH) entrapped tungsten carbide (WC) nanocomposite on its electrochemical performances towards emergent food contaminant, DPA. The importance of the current work is the selection and design of hierarchically structured functional materials especially layered double hydroxides, in virtue of their outstanding properties. These multi-dimensional structures when introduced to form a composite with the highly beneficial tungsten carbide offer excellent characteristics such as exceptional accessibility to active sites, enhanced surface area, and high mass transport and diffusion which serves as advantageous for the electrochemical quantification of DPA. Furthermore, the synergy between FeMn-LDH and WC nanomaterials contributes to the higher active surface area, increased electrical conductivity, fast electron transportation, and ion diffusion, resulting in static properties including a wide linear range (0.01-183.34 µM), low detection limit (1.1 nM), greater sensitivity, selectivity, and reproducibility thus confirming the potential capability of the WC@FeMn-LDH sensor towards the interference-free determination of DPA which validates its practicality and feasibility in real-time. Hence, this work aims to stimulate the fabrication of various advanced hierarchical structures by a simple hydrothermal approach that can have veracity of potential applications.

Hydrophobic deep eutectic solvent-based ultrasonic-assisted liquid-liquid micro-extraction combined with HPLC-FLD for diphenylamine determination in fruit.

In this paper, novel high extraction efficiency hydrophobic eutectic solvents (DESs), n-octanoic acid as a hydrogen bond donor (HBD) and menthol as a hydrogen bond acceptor (HBA), were selected from five hydrophobic DESs to extract trace diphenylamine (DPA) in fruits apple, pear and orange under ultrasonic-assisted liquid-liquid micro-extraction (UA-LLME) technology before high-performance liquid chromatography (HPLC) analysis. Working parameters such as the DESs type, molar ratio, extractant volume, and ultrasonic time of the LLME hydrophobic DESs technology were optimised. Average recoveries between 96% and 108% were obtained on actual samples. This method gave lower detection limit (LOD) than other existing methods due to combining the high-efficiency extraction of hydrophobic DES and high sensitivity of fluorescence detector. This method was sensitive and eco-friendly, and can be used for the determination of trace components in fruits.

Substituted diphenylamine antioxidants (SDPAs) in typical domestic wastewater treatment plants and Songhua River in the northeast of China.

Limited studies focus on the occurrence, removal rate and seasonal variation of substituted diphenylamine antioxidants (SDPAs) in surface water and wastewater in China. In this paper, the detection method of SDPAs was established by the ultra-performance liquid chromatography-tandem mass spectrometry. Daily variations suggested that significant variations were found for the concentrations of some SDPAs in the influent. It was found that the SDPAs could be detected in all the effluent samples and C8/C8-DPA was the predominant compound in two WWTPs. The levels of most SDPAs in the effluent were much lower than that of influent, with the removal efficiencies of total SDPAs ranged from 57.9% to 84.2%. There were significant differences with the SDPA concentrations in the influent between different seasons. Higher concentrations of SDPAs were found at downstream than those of upstream. The results of this study provide more environmental occurrence data and new insights into the research on the environmental fate of these compounds.

A simple GC-MS method for the determination of diphenylamine, tolylfluanid propargite and phosalone in liver fractions.

In this study, an accurate and robust gas chromatography/mass spectrometry method was developed for quantitative analysis of diphenylamine, tolylfluanid, propargite and phosalone in liver fractions. Different injector parameters were optimized by an experimental design technique (central composite design). An optimal combination of injector temperature (°C), splitless time (min) and overpressure (kPa) values enabled to maximize the chromatographic responses. Sample preparation was based on protein precipitation using trichloroacetic acid followed by liquid-liquid extraction (LLE) of the pesticides with hexane. All compounds and endrin as internal standard were quantified without interference in selected ion monitoring mode. The calibration curves for diphenylamine, tolylfluanid, propargite and phosalone compounds were linear over the concentration range of 0.1 to 25 µM with determination coefficients (R2) higher than 0.999. A lower limit of quantification of 0.1 µM was obtained for all analytes, i.e. 422.5, 868.0, 876.2 and 919.5 µg/kg of liver fraction (hepatocytes) for diphenylamine, tolylfluanid, propargite and phosalone, respectively. All compounds showed extraction recoveries higher than 93%, with a maximum RSD of 3.4%. Intra- and inter-day accuracies varied from 88.4 to 102.9% and, imprecision varied from 1.1 to 6.7%. Stability tests demonstrated that all pesticides were stable in liver extracts during instrumental analysis (20 °C in the autosampler tray for 72 h) following three successive freeze-thaw cycles and, at -20 °C for up to 12 months. This simple and efficient analytical procedure is thus suitable for metabolism studies or for assessing mammals liver contamination.

Ultrasound-assisted synthesis of two-dimensional layered ytterbium substituted molybdenum diselenide nanosheets with excellent electrocatalytic activity for the electrochemical detection of diphenylamine anti-scald agent in fruit extract.

Metal chalcogenides with large active sites have been received great attention as an excellent catalyst due to their hierarchical structural properties. Here, we have demonstrated the synthesis of ytterbium-doped molybdenum selenide (YbMoSe2) in the form of two-dimensional nanosheets by using a simple ultrasonic method. The formation of the crystal phase of prepared YbMoSe2 nanosheets was studied by using the selective characterization techniques. The reported HRTEM confirmed that the introduction of heterogeneous spin of Yb with MoSe2 creates the lattice distortion. Thus, the active sites can be increased by creating the lattice distortion on the basal plane of the metal chalcogenides nanosheets. The band gap study was carried out by using UV-visible spectrometer and demonstrated the decreasing band gap of MoSe2 from 1.30 eV to 1.15 eV due to the Yb substitution/doping. The increasing active sites with decreasing band gap facilitate an excellent electronic conductivity and electrochemical activity. Furthermore, the electrocatalytic activity of YbMoSe2 modified glassy carbon electrode (YbMoSe2/GCE) toward the sensing of diphenylamine (DPA) anti-scald agent. As expected, YbMoSe2/GCE showed a high level of electrochemical activity with a low limit of detection (0.004 µM) and excellent sensitivity (11.4 µA µM-1 cm-2) towards the detection of DPA. In addition, the superior selectivity, stability, and reproducibility of YbMoSe2/GCE also were recorded. The beneficial electrochemical activity of YbMoSe2/GCE offered the more advantages to detection of DPA in the food sample also.

Emerging aromatic secondary amine contaminants and related derivatives in various dust matrices in China.

Aromatic secondary amines (Ar-SAs), constituted of several analogues with varied substitutions in molecular structure, are among the most frequently used anthropogenic antioxidants. Despite the reported toxicity effects, little information is available on their environmental contamination, except for few particular congeners such as diphenylamine. In this study, the occurrence of two kinds of Ar-SAs, substituted diphenylamines (S-DPAs) and novel substituted p-phenylenediamines (S-PPDs), was investigated in dust samples collected from outdoor rubber playgrounds and residential houses. Seven S-DPAs (GM: 102 ng/g) and two S-PPDs (GM: 20.9 ng/g) were detected in indoor dust. Significantly higher concentrations of S-DPAs (GM: 422 ng/g) and S-PPDs (GM: 31.6 ng/g) were observed in playground dust (p < 0.05). Different dominant Ar-SA congeners were found for indoor dust (low molecular weight Ar-SAs) and playground dust (high molecular weight Ar-SAs), indicating varied sources of Ar-SAs for different dust matrices. Apart from these parent chemicals, three diphenylamine derivatives, including N-nitrosodiphenylamine, 2-nitrodiphenylamine, and 4-nitrodiphenylamine, were also confirmed in indoor dust (GM: 35.7 ng/g) and playground dust (GM: 7.88 ng/g). A preliminary estimated daily intake calculation via dust ingestion indicated no immediate health risk to Chinese population. To our knowledge, this is the first report on the occurrence of a wide range of Ar-SAs and related derivates in dust matrices.

[Detecting the concentrations of diphenylamine in air of workplace with HPLC].

Objective: To establish the method of detecting the concentrations of diphenylamine in air of workplace with high performance liquid chromatographic (HPLC) . Methods: According to standards of methods for determining the chemical substances in workplace air, diphenylamine in the air was collected by glass fiber filter treated with sulfuric acid, then dissolved by methanol and determined by high performance liquid chromatography with UV-detector. Results: There was a linear relationship within the range of 0-30.0 µg/ml, and regression equation was y=8425.6x-150.7, correlation coefficient was 0.999 9, the detection limit was 0.045 µg/ml. The lowest detected concentration was 0.030 mg/m(3) (sampling volume 15 L) . The within-run precision was 2.41 ℅-3.02%, the between-run precision was 3.11%-4.45%. The desorption efficiencies was 97.8℅ and the sampling efficiencies were 100%. The samples in glass fiber filter could be stored for 7 d at room temperature. Conclusion: The present method could meet with the requirements of Guide for establishing occupational health standards-Part 4 Determination methods of air chemicals in workplace and be feasible for determination of diphenylamine in workplace air.

Determination of Diphenylamine in Agricultural Products by HPLC-FL.

A method for the determination of diphenylamine in agricultural products was developed. Diphenylamine was extracted with acetonitrile from a sample under an acidic condition, passed through a C18 cartridge column, re-extracted with n-hexane, cleaned up on a PSA cartridge column, determined by HPLC with fluorescence detector and confirmed by liquid chromatography with tandem mass spectrometry. Average recoveries (n=5) from brown rice, corn, soybeans, potato, cabbage, eggplant, spinach, orange, apple and green tea were in the range from 76.7 to 94.9%, and the relative standard deviations were from 0.6 to 5.8% at concentrations equal to the maximum residue limits (MRLs). The quantification limits were 0.01 mg/kg, which is the uniform limit in the positive list system for agricultural chemical residues in food in Japan.

Determination of substituted diphenylamines in environmental samples.

Owing to their stability at high temperature, low biodegradation, low water solubility, and low vapor pressure, substituted diphenylamines are used as antioxidants in rubber, foamed polymers, and as high-temperature functional fluids (e.g., lubricants, gear oils, and hydraulic fluids). There are few existing environmental measurements of these substances in any environmental medium. In this study, a method was developed for the determination of 10 substituted diphenylamines in wastewater, biosolids, and sediments using gas chromatography-tandem mass spectrometry (GC-MS/MS). The substituted diphenylamines that were measured were two styrenated diphenylamines isomers, three di-styrenated diphenylamine isomers, tert-butyl-diphenylamine, tert-octyl-diphenylamine, di-tert-butyl-diphenylamine, tert-butyl/tert-octyl-diphenylamine, and di-tert-octyl-diphenylamine. The instrument limits of detection (LODs) and limits of quantitation (LOQs) were 0.02-0.1 and 0.06-0.3 ng mL-1, respectively. Target compounds were spiked into sediment, effluent water, influent water, and biosolids at the 100- and 1000-ng levels (N = 6). Analyte recoveries ranged from 71.5 to 117 % with relative standard deviations (RSDs) of 2.12-12.4 %. The method was applied to the analysis of influent, effluent, and biosolid samples; the sum of substituted diphenylamines were 48.1-713, 1.04-28.5 ngL-1, and 85.3-1184 ngg-1dw (median: 71.0, 7.30 ngL-1, and 402 ngg-1dw), respectively. Nine sediment samples collected in Ontario, Canada contained concentrations of the sum of substituted diphenylamines ranging from 1.55 to 897 ngg-1dw.

Simultaneous determination of substituted diphenylamine antioxidants and benzotriazole ultra violet stabilizers in blood plasma and fish homogenates by ultra high performance liquid chromatography-electrospray tandem mass spectrometry.

Analytical methods were developed for the determination of eight substituted diphenylamines (SDPAs) and six benzotriazole UV stabilizers (BZT-UVs) in blood plasma and fish homogenate matrices. Liquid-liquid extraction by methyl tert-butyl ether and denaturation by KOH following silica gel packed column clean-up was employed for blood plasma preparation. For the fish homogenate samples, ultrasonic assisted solvent extraction combined with automated gel permeation chromatography and silica gel packed column clean-up was used. The target compounds were determined by optimized ultra performance liquid chromatography-tandem mass spectrometry in positive electrospray ionization mode. The method limits of quantification (MLOQs) of the 14 analytes ranged from 0.002 to 1.5ngg(-1) and 0.001 to 2.3ngg(-1) (wet weight, w.w.) for blood plasma and fish homogenate, respectively. The total recoveries of the target compounds varied from 61% to 100% (mean 77±9%). Eleven targets including monobutyl- (C4), dibutyl- (C4C4), monooctyl- (C8), monobutyl monooctyl- (C4C8), dioctyl-(C8C8), monononyl- (C9), dinonly-(C9C9) and 4,4'-bis(α,α-dimethylbenzyl)-(diAMS) DPAs, as well as 2-(2H-Benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (UV234), 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl) phenol (UV327) and 2-(2H-Benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV328) were identified in the environmental biota samples, with concentrations in the range of

Gold nanoparticle-enhanced target for MS analysis and imaging of harmful compounds in plant, animal tissue and on fingerprint.

Gold nanoparticle-enhanced target (AuNPET) was used for detailed investigation of various materials of biological origin - human fingerprint, onion bulb and chicken liver. Analysis of these objects was focused on toxic and harmful compounds - designer drug containing pentedrone, diphenylamine in onion and potentially cancerogenic metronidazole antibiotic in liver. Detection of large quantity of endogenous compounds from mentioned objects is also shown. Most of analyzed compounds were also localized with MS imaging and relationship between their function and location was discussed. Detected compounds belong to a very wide range of chemical compounds such as saccharides, ionic and non-ionic glycerides, amino acids, fatty acids, sulfides, sulfoxides, phenols etc. Fingerprint experiments demonstrate application of AuNPET for detection, structure confirmation and also co-localization of drug with ridge patterns proving person-drug contact.

Diphenylamine and derivatives as predictors of gunpowder age by means of HPLC and statistical models.

The gunpowder age is information of great importance that could help to establish safety regulations related to the propellants use and manipulation. In this work, a forced aging treatment (65°C for 120 days) was applied to four gunpowders stabilized with diphenylamine (DPA). The evolution of DPA and derivatives (N-nitroso-DPA, 2-nitro-DPA, 4-nitro-DPA, and 4-4'-dinitro-DPA) concentration during the days was leaded by High Performance Liquid Chromatography (HPLC). The variation with time of the peak areas of these compounds was used to construct different statistical models that could predict the gunpowders age. These models were validated using nitrocellulose-based gunpowders of known manufacture date. Models that best predicted the gunpowder age provided prediction errors lower than 6, 4, and 2 years for single-base gunpowders with dinitrotoluene (≥ 10%(m/m)), single-base gunpowders and double-base gunpowders, respectively.

Design of molecularly imprinted polymers for diphenylamine sensing.

A series of the polymers imprinted with diphenylamine (DPA) and respective non imprinted polymers were synthesized using precipitation polymerization. Synthesized polymers were characterized by Fourier Transform Infra-Red spectroscopy with Total Attenuated Reflectance (FTIR-ATR), Scanning Electron Microscopy (SEM) and equilibrium batch re-binding experiments. Influence of the synthesis conditions, namely monomer/template ratio and reaction duration, on the polymer binding capacity and selectivity towards aromatic compounds was investigated. Binding behavior of MIP was described using Freundlich isotherm. Significance of the effects of the synthesis conditions on the polymer properties was evaluated using ANOVA. MIPs synthesized at different conditions, which displayed different properties (binding capacity and selectivity), and respective non-imprinted polymers were employed for the fabrication of the potentiometric sensors. While sensors prepared using imprinted polymers had higher sensitivity and selectivity compared to the ones containing non-imprinted polymer, no difference was observed between sensors containing different imprinted polymers. No correspondence between polymers' characteristics obtained in the equilibrium re-binding studies and potentiometric behavior of the sensors based on the same polymers was observed. Therefore, equilibrium re-binding studies cannot be used for predicting sensor behavior.

Diphenylamine residues in apples caused by contamination in fruit storage facilities.

The potential of fruit storage facilities that are contaminated with the widely used chemical antioxidant diphenylamine to cross-contaminate untreated apples (Malus × domestica Borkh.) was studied. A new sample preparation method identified the storage room paint, contaminated from past treatments, as the major source of cross-contamination in the analyzed facilities. Diphenylamine amounts of up to 917 g were found in a single storage room and were shown to correlate with the extent of cross-contamination on stored apples. Our data support a diffusion-based mechanism where the wall paint releases the antioxidant to the storage room atmosphere even years after the last treatment. Given the extent of cross-contamination found in our model experiments and under commercial storage conditions, we deduce a significant risk of exceeding the potentially upcoming maximum residue level of 0.01 mg kg(-1) on stored fruit in contaminated rooms even years after the last diphenylamine treatment.

In situ analysis of agrochemical residues on fruit using ambient ionization on a handheld mass spectrometer.

We describe a rapid in situ method for detecting agrochemicals on the surface or in the tissue of fruit using a portable mass spectrometer equipped with an ambient ionization source. Two such ionization methods, low temperature plasma (LTP) and paper spray (PS), were employed in experiments performed at a local grocery store. LTP was used to detect diphenylamine (DPA) directly from the skin of apples in the store and those treated after harvest with DPA were recognized by MS and MS/MS. These data therefore allowed ready distinction between organic and non-organic apples. DPA was also found within the internal tissue of purchased apples and its distribution was mapped using LTP. Similarly, thiabendazole residues were detected on the skin of treated oranges in a grocery store experiment in which paper spray was performed by wiping the orange surface with a moist commercial lens wipe and then applying a high voltage to ionize the chemicals directly from the wipe. The handheld mass spectrometer used in these measurements is capable of performing several stages of tandem mass spectrometry (up to MS(5)); the compounds on the fruit were identified by their MS/MS fragmentation patterns. Protonated DPA (m/z 170) produced a characteristic MS(2) fragment ion at m/z 92, while thiabendazole was identified by MS(3) using precursor to fragment ion transitions m/z 202 →m/z 175 →m/z 131. These particular examples exemplify the power of in situ analysis of complex samples using ambient ionization and handheld mass spectrometers.

[Study on the chemical constituents in the volatile oils of the flowers of Tibetan medicine Rhododendron anthopogon].

OBJECTIVE: To study the chemical constituents of the volatile oils from the flowers of Rhododendron anthopogon D. Don. METHODS: The volatile oils from the flowers of Rhododendron anthopogon D. Don were extracted by water steam distillation and its chemical constituents were separated and identified by GC-MS. The content of each constituent was determined by area normalizetion method. RESULTS: Fifty peaks were separated and forty seven components were identified, which constituted about 97.44% of the total essential oils. CONCLUSIONS: The main compounds are N-acetyl-1, 2, 3, 4-tetrahydro-isoquinoline (29.23%), 2-Ethoxypropane (12.47%), 3-Methyl-6-tert-butylphenol (10.83%), 3-Methyl-5-phenyl-isothiazole (6.38%), Diphenylamine (4.20%), N-ethyl-1, 2,3,4-tetrahydro-naphthalenamine (3.62%), Pentacosane (3.12%) and Tricosane (3.06%).

New protocol for the isolation of nitrocellulose from gunpowders: utility in their identification.

In this work, a new approach for the isolation of nitrocellulose from smokeless gunpowders has been developed. A multistep solvent extraction method was needed to purify nitrocellulose contained in gunpowders. For single-base or double-base gunpowders six consecutive solvent extractions were selected: three extractions with methanol (to remove nitroglycerin, 2,4-dinitrotoluene, ethyl-centralite, diphenylamine, and diphenylamine derivatives); one extraction with dichloromethane (to remove colorants and plasticizers of organic nature); one extraction with methanol (to facilitate a final polar extraction); and one extraction with water (to remove ionic components) were necessary at 35 degrees C. For the triple-base gunpowder studied, eight solvent extractions were needed due to a high concentration of the water-soluble nitroguanidine was present. In addition to the same five initial phases used for the single-base and double-base gunpowders, three water extraction phases at a higher temperature (75 degrees C instead of 35 degrees C) were also needed. A final step to solubilize nitrocellulose in methyl ethyl ketone was used to remove inert components (mainly graphite). Nitrocellulose isolated from these propellants was characterized by Fourier-Transformed Infrared Spectroscopy (FTIR spectroscopy). The same FTIR spectra were observed for nitrocelluloses isolated from different types of gunpowders. A comparison of FTIR spectra of nitrocellulose samples of different nitration degree evidenced that the bands regions most affected by this factor were: 3600-3400cm(-1), corresponding to the stretching vibrations of residual hydroxyl groups; 1200-1000cm(-1), attributed to the valence vibrations nuCO of the glucopyranose cycle; and 750-690cm(-1), assigned to vibrations of the nitrate group. In both cases, the bands appearing in these regions were more pronounced in the spectra of nitrocellulose samples of low nitration degree.

Dynamic planar solid phase microextraction-ion mobility spectrometry for rapid field air sampling and analysis of illicit drugs and explosives.

A preconcentration device that targets the volatile chemical signatures associated with illicit drugs and explosives (high and low) has been designed to fit in the inlet of an ion mobility spectrometer (IMS). This is the first reporting of a fast and sensitive method for dynamic sampling of large volumes of air using planar solid phase microextraction (PSPME) incorporating a high surface area for absorption of analytes onto a sol-gel polydimethylsiloxane (PDMS) coating for direct thermal desorption into an IMS. This device affords high extraction efficiencies due to strong retention properties at ambient temperature, resulting in the detection of analyte concentrations in the parts per trillion range when as low as 3.5 L of air are sampled over the course of 10 s (absolute mass detection of less than a nanogram). Dynamic PSPME was used to sample the headspace over the following: 3,4-methylenedioxymethamphetamine (MDMA) tablets resulting in the detection of 12-40 ng of piperonal, high explosives (Pentolite) resulting in the detection of 0.6 ng of 2,4,6-trinitrotoluene (TNT), and low explosives (several smokeless powders) resulting in the detection of 26-35 ng of 2,4-dinitrotoluene (2,4-DNT) and 11-74 ng of diphenylamine (DPA).

Analysis of essential oils from different organs of Scutellaria baicalensis.

OBJECTIVE: To evaluate the differences among essential oils from the fresh flowers, stem leaves, roots and seeds of Scutellaria baicalensis. METHODS: The oils was obtained by hydrodistillation and identified by gas chromatography-mass spectrometry (GC-MS) and the Kovats retention index. The relative contents of the components were determined by the peak-area normalization method adopted in gas chromatography. RESULTS: Fifty-three compounds constituting 91.16% of flower oil, forty-eight compounds comprising 88.48% of stem-leaf oil, thirty-nine compounds representing 91. 79% of root oil and thirty-two compounds accounting 84.58% of seed oil have been identified. CONCLUSION: The results showed that the components and relative contents of the essential oils among flowers, stem leaves, roots and seeds have significant differences. Each of them had a great range of potential utilities and a prospect of development.

Characterization of smokeless powders using nanoelectrospray ionization mass spectrometry (nESI-MS).

Smokeless powder is one of the most common types of explosives used in civilian ammunition and, hence, its detection and identification is of great forensic value. Based on comparison of physical properties, extraction yield in methanol, and the spectra obtained using nanoelectrospray ionization and multistage tandem mass spectrometry (MS/MS) in a quadrupole ion trap mass spectrometer, a method was developed to identify and differentiate unburned smokeless powders from different brands of ammunition. The mass spectrometry method was optimized for the simultaneous detection of the organic stabilizers commonly present in smokeless powders: methyl centralite, ethyl centralite, and diphenylamine. All but two of the powders were differentiated; however, the two that were not differentiated were produced by the same manufacturer. Gunshot residue from the cartridges was deposited on cotton cloth and collision-induced dissociation MS/MS was used to identify low levels of ethyl centralite in the residue, despite the presence of contaminants.