Preparation of Nitroanilines by Ammonolysis of Multinitrobenzenes

Highly efficient ammonolysis of several multinitrobenzenes to the corresponding nitroanilines was achieved by aqueous ammonia. o-Dinitrobenzene on reaction with 8 equiv. of ammonia produce the o-nitroaniline in yields of 87%. Similar reactions with p-dinitrobenzene, m-dinitrobenzene, and trinitrobenzene produce p-nitroaniline, m-nitroaniline, and 3,5-dinitroaniline, in yields of 86%, 45%, and 84%, respectively.     

取代苯分子二阶非线性光学系数的理论计算

用INDO/CI方法研究了苯胺、硝基苯、邻硝基苯胺、间硝基苯胺、对硝基苯胺、2,4-二硝基苯胺的二阶非线性光学极化系数βijk, 用自编程序计算得到的矢量元βx和实验结果相当符合, 表明分子内电子受体和给体之间的电荷转移量和电荷转移的可能性共同决定βx。     

Simultaneous spectrophotometric determination of nitroaniline isomers after cloud point extraction by using least-squares support vector machines

Cloud point extraction has been used for the preconcentration of m-nitroaniline, o-nitroaniline and p-nitroaniline and later simultaneous spectrophotometric determination using polyethylene glycol tert-octylphenyl ether (Triton X-100) as surfactant. The resolution of a ternary mixture of the nitroaniline isomers (after extraction by cloud point) by the application of least-squares support vector machines (LS-SVM) was performed. The chemical parameters affecting the separation phase and detection process were studied and optimized. Under the optimum experimental conditions (i.e. pH 7.0, Triton X-100=0.6%, equilibrium time 20 min and cloud point 75 degrees C), calibration graphs were linear in the range of 0.2-20.0, 0.1-15.0 and 0.1-17.0 microg ml(-1) with detection limits of 0.08, 0.05 and 0.06 microg ml(-1) for m-nitroaniline, o-nitroaniline and p-nitroaniline, respectively. The experimental calibration matrix was designed with 21 mixtures of these chemicals. The concentrations were varied between calibration graphs concentrations of nitroaniline isomers. The root mean square error of prediction (RMSEP) for m-nitroaniline, o-nitroaniline and p-nitroaniline were 0.0146, 0.0308 and 0.0304, respectively. This procedure allows the simultaneous determination of nitroaniline isomers in synthetic and real matrix samples good reliability of the determination was proved.     

Application of vortex-assisted supramolecular solvent liquid–liquid microextraction for trace determination of nitroaniline isomers

A novel, fast and efficient method for the analysis of nitroaniline isomers as model compounds was developed using vortex-assisted supramolecular solvent liquid–liquid microextraction (VA-SMS-LLME). A vortex mixer was used as the mixer in supramolecular solvent liquid–liquid microextraction, and it decreased the extraction time greatly. Several important parameters influencing extraction efficiency, such as the type and volume of extraction solvent, pH of sample, salt effect and extraction time, were optimised in detail. Under the optimal conditions, the enrichment factor was 133 for p-nitroaniline, 98 for m-nitroaniline and 115 for o-nitroaniline, and the limits of detection by HPLC were 0.3, 1.0 and 0.5 μg L^?1, respectively. Linearity with determination coefficient from 0.9981 to 0.9993 was evaluated using water samples spiked with the nitroanilines at fourteen different concentration ranging from 4 to 1000 μg L^?1. The ranges of intra-day and inter-day precision (n = 5) at 10 μg L^?1 of nitroanilines were 1.67–7.05% and 9.4–11.6%, respectively. The VA-SMS-LLME method was successfully applied for preconcentration of nitroanilines in environmental water samples.     

Nachweis und Bestimmung isomerer Nitroaniline

Zusammenfassung m-Nitroanilin entfärbt sich in verdünnter Lösung mit Säure, die anderen zwei Isomeren nicht. Auf dieser Basis kann man m-Nitroanilin neben den anderen Isomeren bestimmen. Werden Nitroaniline diazotiert und mit -Naphthylamin oder Anilin gekuppelt, so entstehen Säure-Base-Indicatoren. Die Farbe der Azoverbindung ist in alkalischem Medium bei der p-Nitroanilinverbindung am stärksten, bei o-Nitroanilin schwächer und bei m-Nitroanilin am schwächsten. Auf dieser Basis wurde eine Methode zum Nachweis und zur Bestimmung von p-Nitroanilin neben o- bzw. m-Nitroanilin und von o-Nitroanilin neben m-Nitroanilin ausgearbeitet. Außerdem wird eine andere Reaktion zum Nachweis isomerer Nitroaniline mitgeteilt, bei der die diazotierten Nitroaniline mit 1-Naphthol-4-sulfonsäure gekuppelt werden. Auf diese Weise erhält man einen Säure-Base-Indicator aus p-Nitroanilin, eine Azoverbindung von geringem Säure-Base-Charakter aus m-Nitroanilin und keinen Indicator aus o-Nitroanilin. Die Azoverbindungen aus Nitroanilinen und 1-Naphthol-4-sulfonsäure führen zu verschieden gefärbten Mg-Komplexen.

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Summary A determination of m-nitroaniline in presence of the other isomers is based on the fact that only the m-compound is decolorized in dilute acid solution. When nitroanilines are diazotized and coupled with -naphthylamine or aniline acid-base indicators are formed, which can be applied to the identification and determination of p-nitroaniline in presence of o- or m-nitroaniline and of o-nitroaniline in presence of the m-compound, as the colours of the azo compounds in alkaline solution are of different strengths. Another reaction useful for the identification of the isomeric nitroanilines is the coupling of the diazotized compounds with 1-naphthol-4-sulphonic acid yielding acid-base indicators of different character, from which differently coloured magnesium complexes may be obtained.

     

Determination of tocopherols,tocopherolquinones and tocopherolhydroquinones by gas chromatography-mass spectrometry and preseparation with lipophilic gel chromatography

A method has been developed for the simultaneous determination of a range of aromatic amines using cation-exchange chromatography performed on a standard ion chromatography column using d.c. amperometric detection. The analytes separated were 2,4- and 2,6-toluenediamine (2,4- and 2,6-TDA), aniline, o-toluidine, benzidine, p-chloroaniline, 4,4'-diaminodiphenyl (4,4'-DDP), m-nitroaniline and 1-naphthylamine. A Dionex CS12 column was used with gradient elution from an initial eluent of 5% CH3CN+35 mM H2SO4 to 27% CH3CN+35 mM H2SO4 (at 35 min). Detection limits in the range 2.6-22.6 microg/l were observed for all analytes except m-nitroaniline, for which the detection limit was 201 microg/l. Linear calibrations and good precision were observed and the method was applied to the determination of benzidine, p-chloroaniline and 1-naphthylamine in wastewater samples. Further, the separation was also used (after some modification of the eluent conditions) for the determination of 2,4- and 2,6-toluene diisocyanate (2,4- and 2,6-TDI) and 4,4'-methylenediphenyl diisocyanate (4,4'-MDI) after their hydrolysis to 2,4-TDA, 2,6-TDA and 4,4'-DDP. Detection limits for 2,6- and 2,4-TDI and 4,4'-MDI were 3.8, 8.2, and 11.2 microg/l, respectively. The method was applied to the determination of diisocyanates in air.     

A dinitrophenylation method for the micro-determination of amide nitrogen

A new micro-method is reported for the determination of amide nitrogen, based on the estimation of 2,4-dinitroaniline produced by the reaction between ammonia, quantitatively liberated from the protein, and 1-fluoro-2,4-dinitrobenzene. Application of the method to 0.5-mg samples of wool gives results in agreement with those obtained by other authors for the same type of wool. Analyses of cuticle-rich material obtained from these wool samples show that in one sample out of three the cuticle is significantly poorer in amide groups than the whole fibre The mean standard error taken over all the analyses is 4 5 %.     

Enzyme-linked immunosorbent assays for the sensitive analysis of 2,4-dinitroaniline and 2,6-dinitroaniline in water and soil

The development and characterization of one rat monoclonal antibody (mAb) for 2,4-dinitroaniline and of two rat mAbs for 2,6-dinitroaniline are described. With the immunization of rats with 2,4,6-trinitrophenyl-glycylglycine–keyhole limpet hemocyanine (KLH) conjugate one mAb (PK 5H6) has been developed and formatted into a competitive enzyme-linked immunosorbent assay (ELISA). This assay no. 1 is very sensitive for 2,4-dinitroaniline with a test midpoint of 0.24 ± 0.06 μg L⁻¹ (n = 19) in 40 mM phosphate-buffered saline (PBS). A second hapten, 3-(4-amino-2,6-dinitrophenyl)propionic acid, which was also conjugated to KLH and used for the immunization of rats, led to two sensitive ELISAs for 2,6-dinitroaniline in 40 mM PBS with test midpoints of 0.61 ± 0.08 μg L⁻¹ (n = 15; mAb DNT4 3C6; assay no. 2) and 0.94 ± 0.29 μg L⁻¹ (n = 17; mAb DNT4 1A7, assay no. 3). Selectivities of all mAbs were checked with more than 20 compounds, including nitroaromatic compounds, 2,6-dinitroaniline pesticides, and other substituted derivatives of aniline. As very noticeable cross-reactivities, all mAbs recognize 2-chloro-4,6-dinitroaniline, 4-chloro-2,6-dinitroaniline and 2-bromo-4,6-dinitroaniline, the last of these being a major metabolite of the azo dye Disperse Blue 79. As first demonstrations of applications, two ELISAs (assays no. 1 and 2) were used for the analysis of 2,4- or 2,6-dinitroaniline in spiked water and soil samples. Recovery data were determined and the majority of these data were in the range of 90–120%. These assays can contribute to a very cost-effective and environmentally friendly immunochemical surveillance monitoring of environmental samples for contaminations with these compounds. To the best of the authors’ knowledge, these are the first antibodies described for 2,4-dinitroaniline and for 2,6-dinitroaniline.     

Selective determination of 2,4-xylenol by gas chromatography/supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry

Gas chromatography/supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (GC/SSJ/REMPI/TOF-MS) was employed for isomer-selective determination of 2,4-xylenol in river and seawater samples. The sample containing 2,4-xylenol was measured using argon, rather than helium, as the GC carrier gas to cool the analyte molecule sufficiently. The instrumental detection limit (IDL) achieved at a flow rate of 1 mLmin(-1) was 14 pg. Although this value was comparable to the value (ca. 10 pg) obtained by gas chromatography/electron impact/quadrupole mass spectrometry (GC/EI/QMS). When the flow rate was increased to 8 mLmin(-1), interference from the 2,5-xylenol isomer was completely suppressed. The IDL was degraded to 83 or 160 pg at a flow rate of 5 or 8 mLmin(-1), respectively. The recovery of 2,4-xylenol from the river and the seawater samples was 85 and 93%, respectively. The time for analysis was only 10 min per one sample in GC/SSJ/REMPI/TOF-MS. These results suggest that GC/SSJ/REMPI/TOF-MS is useful for the selective measurement of 2,4-xylenol, which has been designated a Class I chemical substance in the Pollutant Release and Transfer Register (PRTR).     

替代模板印迹-高效液相色谱测定空气PM2.5中的羰基化合物

以替代模板法制备了分子印迹固相萃取柱（MISPE），该柱能够有效去除空气PM2.5样品分析过程中过量的衍生剂2，4-二硝基苯肼（2，4-DNPH），并能够大幅度浓缩样品溶液，提高羰基化合物的富集效率和监测灵敏度，缩短采样时间。与高效液相色谱联用，实现了对空气PM2.5中的羰基化合物的快速检测。本研究解决了传统固相萃取材料选择性低，不能去除2，4-DNPH干扰的瓶颈问题。本方法用于研究广州市大学城早春季节雾霾天和非霾天羰基化合物水平及其来源，结果发现无论是灰霾天气还是正常天气，14种目标羰基化合物均被检出。研究发现，在污染物排放和天气因素的影响下，灰霾天气羰基化合物总量增高，尤其是异戊醛增长迅速，并且与丙醛浓度变化呈现高度正相关。通过相关性分析，证明除了光化学反应等自然因素，人类活动对广州羰基化合物水平的干扰严重，应引起重视。     

Reduction of Cr(VI) in presence of some amino compounds

The rate of reduction of Cr(VI) to Cr(III) in 0.05 M K2Cr2O7 has been studied and was found to be first order. The rate of reaction was measured in the absence of amino compounds and in the presence of o-nitroaniline, p-nitroaniline, m-toulidine, p-chloroaniline, and o-bromoaniline at four different temperatures. The rate of reaction was found to decrease with the addition of amines. Thermodynamic parameters DeltaG*, DeltaH*, and DeltaS* were calculated from the study.     

Sensitive determination of strongly polar aromatic amines in water samples by stir bar sorptive extraction based on poly(vinylimidazole-divinylbenzene) monolithic material and liquid chromatographic analysis

A simple and sensitive method for the determination of polar aromatic amines (PAAs) was developed using stir bar sorptive extraction (SBSE) coupling to high-performance liquid chromatography. A hydrophilic poly(vinylimidazole-divinylbenzene) (VIDB) monolithic material was prepared and acted as SBSE coating. The influences of polymerization conditions for VIDB on the extraction efficiency were investigated using aniline and 2,4-dinitroaniline as detected solutes. To achieve optimum extraction performance for PAAs, several parameters including extraction and desorption time, desorption solvent, ionic strength and pH value of sample matrix were investigated. The results showed that under the optimized experimental conditions, the method showed good sensitivity and excellent recoveries, as well as advantages such as linearity, simplicity, low cost and high feasibility. The extraction performance of present method to the target compounds also compared with commercial SBSE which using polydimethylsiloxane as coating and other SBSE which based on monolithic materials. Finally, the proposed method was successfully applied to the determination of PAAs in lake and sea waters, and excellent recoveries of spiked target compounds in real samples were obtained.     

Determination of dye intermediates in oxidative hair dyes by fused-silica capillary gas chromatography

A fused-silica capillary gas chromatographic method is described for the determination of dye intermediates in oxidative hair dyes. An appropriate amount of hair dye sample is dissolved in 10 ml of methanol containing 0.25 g of ammonium thioglycolate and an appropriate amount of 2-amino-4-methylphenol as an internal standard. This solution is directly injected into a gas chromatograph. A fused-silica capillary column with cross-linked methyl silicone OV-1 or SE-54 as a liquid phase yields excellent resolution of dye intermediates. Some factors affecting the quantitation of dye intermediates are discussed. The proposed method gave good recoveries and reproducibilities, and permits simultaneous determination of various types of dye intermediates without any pretreatment. The use of a nitrogen-phosphorus detector allows the selective detection of nitrogen-containing dye intermediates. This simple and versatile method is applicable for the determination of dye intermediates in commercial hair dyes.     

Application of NaClO-treated multiwalled carbon nanotubes as solid phase extraction sorbents for preconcentration of trace 2,4-dichlorophenoxyacetic acid in aqueous samples

Multiwalled carbon nanotubes functionalized by oxidation of original multiwalled carbon nanotubes with NaClO were prepared and their application as solid phase extraction sorbent for 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated systemically, and a new method was developed for the determination of trace 2,4-D in water samples based on extraction and preconcentration of 2,4-D with solid phase extraction columns packed with NaClO-treated multiwalled carbon nanotubes prior to its determination by HPLC. The optimum experimental parameters for preconcentration of 2,4-D, including the column activating conditions, the amount of the sorbent, pH of the sample, elution composition, and elution volume, were investigated. The results indicated 2,4-D could be quantitatively retained by 100 mg NaClO-treated multiwalled carbon nanotubes at pH 5, and then eluted completely with 10 mL 3:1 (v/v) methanol-ammonium acetate solution (0.3 mol/L). The detection limit of this method for 2,4-D was 0.15 μg/L, and the relative standard deviation was 2.3% for fortified tap water samples and 2.5% for fortified riverine water sample at the 10 μg/L level. The method was validated using fortified tap water and riverine water samples with known amount of 2,4-D at the 0.4, 10, and 30 μg/L levels, respectively.     

高效液相色谱法同时测定氧化型染发产品中33种染发剂

建立了高效液相色谱同时测定氧化型染发产品中33种禁限用染发剂含量的分析方法。采用Waters Atlantis^® T3 MV Kit色谱柱（250 mm×4.6 mm，5 μm），以磷酸盐缓冲液-乙腈为流动相，梯度洗脱，流速为1.0 mL/min，柱温为25℃；采用二极管阵列检测器（DAD），检测波长为235及280 nm，进样量为5 μL。结果表明，各成分在线性范围内线性关系良好，相关系数均高于0.999，各成分精密度实验相对标准偏差（RSDs）均小于2%；四氨基嘧啶硫酸盐和2，4-二氨基苯氧基乙醇盐酸盐在12 h内稳定性实验RSDs小于5%，其余31种成分在24 h内稳定性实验RSDs均小于5%；各成分在3个浓度水平下的加标回收率为77.6%~116.3%。该方法简便、快速、准确，适用于氧化型染发产品中多种染发剂的检测。     

Evaluation of feed-forward back propagation and radial basis function neural networks in simultaneous kinetic spectrophotometric determination of nitroaniline isomers

Mixtures of 2-, 3-, and 4-nitoroanilines, are simultaneously analyzed with spectrophotometry, based on their different kinetic properties. These nitroanilines react differentially with 1,2-naphtoquinone-4-sulphonate (NQS) at pH 7 in micellar medium to produce colored product. The differential kinetic spectra were monitored and recorded at 500 nm, and the data obtained from the experiments were processed by chemometric approaches, such as back-propagation neural networks (BPNNs), radial basis function neural networks (RBFNNs), and partial least squares (PLS). Experimental conditions were optimized and training the network was performed using principal components (PCs) of the original data. A set of synthetic mixtures of nitroanilines was evaluated and the results obtained by the application of these chemometric approaches were discussed and compared. The analytical performance of the models was characterized by relative standard errors. It was found that the artificial neural networks model affords relatively better results than PLS. The proposed method was applied to the determination of considered nitroanilines in water samples.     

Use of a microcolumn packed with modified carbon nanofibers coupled with inductively coupled plasma mass spectrometry for simultaneous on-line preconcentration and determination of trace rare earth elements in biological samples

In this work, a new method was developed for the determination of trace rare earth elements (REEs) in biological samples by inductively coupled plasma mass spectrometry (ICP-MS) after preconcentration on a microcolumn packed with modified carbon nanofibers (CNFs). CNFs oxidized with nitric acid have been proved to possess an exceptional adsorption capability for REEs due to their surface functionalization. The effects of the experimental parameters, including pH, sample flow rate and volume, elution solution and interfering ions, on the recoveries of the analytes have been investigated systematically. A 100-fold enrichment factor was obtained. The adsorption capacity of CNFs was found to be 18.1, 19.3, 23.6, 17.6, 22.3 and 19.5 mg/g for La, Ce, Sm, Eu, Dy and Y, respectively. Under the optimum conditions, the detection limits of this method ranged from 0.2 pg/mL (Dy) to 1.2 pg/mL (Ce) with an enrichment factor of 15-fold, and the relative standard deviations (RSDs) for the determination of REEs at the 1.0 ng/mL level were less than 4% (n = 9). This method was applied to the analysis of trace REEs in a real sample of human hair with recoveries of 95-115%. In order to validate the proposed method, a certified reference material of human hair (GBW 07601) was analyzed with satisfactory results.     

Core-shell microgel stabilized silver nanoparticles for catalytic reduction of aryl nitro compounds

Silver nanoparticles loaded into shell of poly (styrene-N-isopropylmethacrylamide-co-acrylic acid) core shell [P (SNA-CS)] gel particles were synthesized and analyzed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis) and dynamic light scattering (DLS). Catalytic activity of Ag@P (SNA-CS) particles was investigated by reducing p-nitroaniline (p-NA) into p-aminoaniline (p-AA) in the presence of sodium borohydride (NaBH₄) reductant. Molecules of the substrate adsorbed on the surface of silver nanoparticles interact with borohydride ions (BH₄⁻) to form p-AA. Other nitroarenes like o-nitroaniline (o-NA), p-nitrophenol (p-NP) o-nitrophenol (o-NP), 2,4-dinitrophenol(2,4-DNP) were also reduced into their corresponding aryl amines using Ag@P (SNA-CS) composite microgels as catalyst. Reported catalyst efficiently reduced the nitro aromatic compounds individually as well as simultaneously at ambient temperature. Effect of different reaction conditions (catalyst dose, concentration of NaBH₄ and concentration of p-NA) on reaction completion time, value of apparent rate constant (k_app) and reduction efficiency of the catalyst for reduction of p-NA was also demonstrated. Ag@P (SNA-CS) catalyst was found to be able to retain activity up to four cycles.     

Flow Injection Spectrophotometric Determination of 2,4‐D Herbicide

2,4‐Dichlorophenoxy acetic acid herbicide is spectrophotometrically determined by diazotization method in a flow injection assembly. The method is based on base hydrolysis of herbicides. The hydrolyzed product 2,4‐dichlorophenol is reacted with diazotized sulfanilic acid. The absorbance of the resulting coloured product was measured at 480 nm. The calibration graph is linear over the range of 0.2–20 μgmL^?1, with a relative standard deviation of (RSD) of 7.2% and sample throughput of 90 samples h^?1. The % recovery for determination of 2,4‐dichlorophenoxy acetic acid was found to be 92.0–95.3%. The method is easy, simple and faster than the established chromatographic method. The method was applied for determination of 2,4‐dichlorophenoxy acetic acid herbicide in commercial formulations and for residue determination in fruits and food samples.     

A simple,rapid and sensitive method based on modified multiwalled carbon nanotube for preconcentration and determination of lead ions in aqueous media in natural pHs

In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL^?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples.