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1.
Phenol, 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) were baseline separated by using a homemade microchip CE with an end-channel amperometric detector where a 50 microm Pt microdisk working electrode (WE) and a Pt cathode were integrated onto the microchip itself. Separation parameters such as injection time and voltage, pH of the buffer, online pretreatment condition for WE, reproducibility, and detection potential were investigated. Under the selected separation conditions, the linear ranges for phenol, 2,4-DCP, and 2,4,6-TCP were 2-200, 4-400, and 4-400 microM, respectively. The LODs were 0.4, 0.5, and 0.7 microM for phenol, 2,4-DCP, and 2,4,6-TCP, respectively (S/N = 3). The standard addition method was successfully applied to the analysis of landfill leachate samples and the concentration of phenol in the landfill leachate samples was measured to be 0.32 and 0.21 mM, respectively. The recoveries were in the range of 85-103% and corresponding RSDs were less than 5.5%.  相似文献   

2.
实验发现,2,4-二氯苯氧基乙酸(2,4-D)经紫外光转化后与KMnO4在H2SO4介质中反应可产生化学发光。采用液相色谱-质谱联用技术(LC-MS)对2,4-D光降解产物进行分析,推断光降解主要生成了多酚类降解产物,如2-氯对苯二酚(CHQ)和4-氯邻苯二酚等。化学发光光谱研究发现,2,4-D经紫外光转化后,与KMnO4反应的发光波长为690 nm,与2,4-D的典型降解产物CHQ的化学发光光谱一致。此发光现象是氧化还原过程中生成的Mn?吸收反应所释放出的化学能成为激发态,再返回基态时产生的特征辐射峰。该反应体系可用于2,4-D的检测,当2,4-D浓度在0.01~10 mg/L范围内与发光强度呈良好的线性关系;检出限为3.0μg/L。  相似文献   

3.
Homogeneous aqueous solutions of organochlorine pesticides and chlorophenols, namely, lindane, hexachlorobenzene and 2,4-dichlorophenol (2,4DCP), undergo effective photodegradation upon photolysis with UV and near visible light in the presence of a characteristic polyoxometallate catalyst PW12O40 3−. These substrates remained, practically, intact (lindane, HCB) or underwent minor degradation under similar conditions in absence of catalyst. The main oxidant appears to be OH radicals formed by the reaction of the excited polyoxometallate with H2O. The system compares with the widely published TiO2. Chlorohydroquinone (ClHQ), hydroquinone (HQ), chlorobenzoquinone (ClBQ), benzoquinone (BQ), 3,5-dichlorocatechol (3,5DCC) and 4-chlorocatechol (4CC), among others, were identified as the main aromatic intermediates in the photodegradation of 2,4DCP. Acetic acid was detected as ring cleavage product. In all cases the final photodegradation leads to complete mineralization of substrates to CO2 and HCl.  相似文献   

4.
A high-performance liquid chromatography (HPLC) method was developed and validated to determine phenol and potential intermediates from hydroxylation (hydroquinone, benzoquinone, catechol) and hypochlorination (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,3,6-trichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) pathways during electrooxidation in the presence of chloride. A Hypersil ODS column (150 mm L × 4.6 mm I.D.) was used for the separation. The best separation was achieved when using a time variant gradient between a water mobile phase (with 0.1% formic acid adjusted to pH 3.0 with 0.1 mM sulfuric acid) and an organic phase (90:5:5 by volume mixture of acetonitrile:methanol:acetic acid). The flow rate was 0.8 mL min?1 and UV absorbance was monitored at 270, 280, 290 and 300 nm, choosing the wavelength of strongest response for each compound. The intra- and inter-day accuracy and precision were tested using five replicates each day on three consecutive days.  相似文献   

5.
采用循环伏安法和原位红外光谱技术研究了2,4-二氯苯酚在Pt电极上的电化学氧化降解反应,结合Fukui函数值预测了2,4-二氯苯酚在电化学氧化过程中的反应位点. 结果表明,Pt电极对2,4-二氯苯酚有良好的电催化活性,2,4-二氯苯酚在电极表面反应主要有3个途径:直接通过电化学反应脱去氯离子,生成苯酚;在·OH的进攻下,C—Cl键断裂,4位Cl较2位Cl先脱去,生成苯二酚,并可进一步氧化生成苯醌以及不饱和羧酸;在·OH的进攻下发生苯环开环反应,生成含氯不饱和羧酸. 在1700 mV左右,2,4-二氯苯酚可经电化学氧化生成CO2.  相似文献   

6.
The degradation of 2-(2,4-dichlorophenoxy)-5-chlorophenol (triclosan) in chlorinated water samples was investigated. Sensitive determination of the parent compound and its transformation products was achieved by gas chromatography with mass spectrometry detection after sample concentration, using a solid-phase extraction sorbent and silylation of the target compounds. Experiments were accomplished using ultrapure water spiked with chlorine and triclosan concentrations in the low mg/l and ng/ml ranges respectively. Chlorination of the phenolic ring and cleavage of the ether bond were identified as the main triclosan degradation pathways. Both processes led to the production of two tetra- and a penta-chlorinated hydroxylated diphenyl ether, as well as 2,4-dichlorophenol. The formation of 2,3,4-trichlorophenol was not detected in any experiment; however, significant amounts of 2,4,6-trichlorophenol were noticed. All of these five compounds were also identified when triclosan was added to tap-water samples with free chlorine concentrations below 1 mg/l. Minor amounts of three di-hydroxylated phenols, containing from one to three atoms of chlorine in their structures, were also identified as unstable triclosan chlorination by-products. The analysis of several raw wastewater samples showed the co-existence of important concentrations of triclosan and its most stable by-products (2,4-dichlorophenol and 2,4,6-trichlorophenol), reinforcing the potential occurrence of the described transformations when products containing triclosan are mixed with chlorinated tap water.  相似文献   

7.
The present study describes the synthesis and characterization of titania-silica mixed imidazolium based ionic liquid (Ti-Si-IL) as well as evaluation of its adsorption behavior towards the 2,4-dinitrophenol (2,4-DNP) and 2,4,6-trichlorophenol (2,4,6-TCP). Synthesized Ti-Si-IL adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), BET surface area Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA) and elemental analysis (CHN). The adsorption of 2,4-DNP and 2,4,6-TCP on Ti-Si-IL was investigated systematically by evaluating the effects of adsorbent dosage, initial pH, contact time and temperature. Satisfactory adsorption 95% and 65% for 2,4-DNP and 2,4,6-TCP was observed at pH 4 and 6, respectively. The kinetic results for 2,4-DNP and 2,4,6-TCP on Ti-Si-IL indicated that the kinetic data follows pseudo-second-order model (R2 = 0.9985 and 0.9750, respectively). Adsorption isotherms were fitted well by the Langmuir model for 2,4-DNP (qm = 44.64 mg g?1 at 318 K) and Freundlich model for 2,4,6-TCP (KF = 0.63 mg g?1 at 318 K). The +ΔH° and -ΔG° values demonstrated that the adsorption of 2,4-DNP was endothermic and spontaneous in nature. While the -ΔH° and +ΔG° values for 2,4,6-TCP adsorption demonstrated exothermic and comparatively nonspontaneous. During the removal process, the role of different functional groups, cyclic structure was monitored and found that the ionic property as well as π-π interactions of host molecules played important role in the extent of adsorption.  相似文献   

8.
Offline dispersive liquid‐liquid microextraction combined with online pressure‐assisted electrokinetic injection was developed to simultaneously enrich seven phenolic compounds in water samples, followed by determination using capillary electrophoresis, namely phenol, 4‐chlorophenol, pentachlorophenol, 2,4,6‐trichlorophenol, 2,4‐dichlorophenol, 2‐chlorophenol, and 2,6‐dichlorophenol. Several parameters affecting separation performance of capillary electrophoresis and the enrichment efficiency of pressure‐assisted electrokinetic injection and dispersive liquid‐liquid microextraction were systematically investigated. Under the optimal conditions, seven phenolic compounds were completely separated within 14 min and good enrichment factors were obtained of 61, 236, 3705, 3288, 920, 86, and 1807 for phenol, 4‐chlorophenol, pentachlorophenol, 2,4,6‐trichlorophenol, 2,4‐dichlorophenol, 2‐chlorophenol, and 2,6‐dichlorophenol, respectively. Good linearity was attained in the range of 0.1–200 μg/L for 2,4‐dichlorophenol, 0.5–200 μg/L for 4‐chlorophenol, pentachlorophenol, 2,4,6‐trichlorophenol, 2‐chlorophenol, and 2,6‐dichlorophenol, as well as 1–200 μg/L for phenol, with correlation coefficients (r) over 0.9905. The limits of detection and quantification ranging from 0.03–0.28 and 0.07–0.94 μg/L were attained. This two step enrichment method was potentially applicable for the rapid and simultaneous determination of phenolic compounds in water samples.  相似文献   

9.
New perthiophosphonic acid anhydrides (R-PS2)n with R = 2,4,6-tri-iso-propylphenyl and 2,4-di-tert-butyl-6-methylphenyl have been prepared. For the latter case, the isolation of the monomer (n = 1), the 2,4-di-tertbutyl-6-methylphenyl-dithioxophosphorane, and both dimers (n = 2), cis- and trans-2,4-bis(2,4-di-tertbutyl-6-methylphenyl)-2, 4-dithioxo-1, 3, 2, 4-dithiadiphosphetane, has been determined. The new cis and trans dithiadiphosphetanes and dithioxophosphoranes as well as the known compounds (2,4,6-trimethylphenyl-PS2)2 and 2,4,6-tri-tert-butylphenyl-PS2 are characterized by solution and high resolution solid-state 31P and 13C NMR spectroscopy. The existence of a dimer-monomer equilibrium is directly proved by 2D exchange 31P NMR spectroscopy. It is shown that the reaction of the monomer with methanol is faster than the reaction of the dimer with methanol.  相似文献   

10.
In the present study, H2O2/UV-C, Fenton and photo-Fenton treatment of 2,4-dichlorophenol was compared in terms of oxidation products and acute toxicity. The oxidation products were identified by gas chromatography-mass spectroscopy, high performance liquid chromatography and ion chromatography, whereas changes in acute toxicity were evaluated by the Vibrio fischeri luminescence inhibition assay. H2O2/UV-C and photo-Fenton processes ensured complete 2,4-dichlorophenolremoval, detoxification and significant mineralization. Hydroquinone and formic acid were identified as the common oxidation products of the studied advanced oxidation processes investigated. 3,5-dichloro-2-hydroxybenzaldehyde, phenol, 4-chlorophenol and 2,5-dichlorohydroquinone were identified as the additional H2O2/UV-C oxidation products of 2,4-dichlorophenol. Acute toxicity decreased with decreasing 2,4-dichlorophenol and increasing chloride release.  相似文献   

11.
《Electroanalysis》2018,30(2):274-282
Reduced Graphene oxide/ZnO nanoflowers ( rGO/ZnO‐NFs ) composite has been synthesized in‐situ using asymmetric Zn complex ( 1 ) as a single‐source molecular precursor (SSMP) with GO at 150 °C. The rGO/ZnO‐NFs composite was characterized by PXRD, UV‐vis, SEM, EDX mapping, TEM and SAED pattern to confirm its purity and morphology. The rGO/ZnO‐NFs composite shows uniform distribution of nanoflowers on graphene sheets. The modified glassy carbon electrode ( GCE ) was fabricated by drop wise layering of the rGO/ZnO‐NFs composite at the surface of the GCE without using binder. The binder free modified electrode ( GCE‐rGO/ZnO ) was explored for detection of nitroaromatics such as p‐nitro‐phenol ( p ‐NP ), 2,4‐dinitrophenol ( 2,4‐DNP ), 2,4‐dinitrotoluene ( 2,4‐DNT ) and 2,4,6‐trinitrophenol ( 2,4,6‐TNP ). The fabricated sensor showed remarkable response for the both toxicants and explosives. The LOD, sensitivity and linear range for the studied toxicants and explosives were found to be in a good range: p ‐NP= 0.93 μM, 240 μA mM−1 cm−2 and 0.2–0.9 mM; 2,4‐DNP= 6.2 μM, 203 μA mM−1 cm−2 and 0.1–0.9 mM; 2,4‐DNT= 10 μM, 371 μA mM−1 cm−2 and 0.2–0.9 mM; 2,4,6‐TNP= 16 μM, 514 μA mM−1 cm−2 and 0.2–0.9 mM, respectively.  相似文献   

12.
In the formylation reaction of 2,4-dialkylphenol (2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2,4-dimethylphenol) in the presence of hexamethylenetetramine, steric effects of alkyl groups play important roles in forming different types of by-products, namely 2,4-di-tert-butyl-6-[(6,8-di-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (1), 2-tert-butyl-4-methyl-6-[(6-tert-butyl-8-methyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (2) and tris(2-hydroxy-3,5-dimethylbenzyl)amine hydrochlorate (3). These three compounds are fully characterized and single-crystal structures of 1 and 3 are further elucidated.  相似文献   

13.
Brominated phenols 2- and 4-bromophenol (2-BP and 4-BP); 2,4- and 2,6-dibromophenol (2,4-DBP and 2,6-DBP) and 2,4,6-tribromophenol (2,4,6-TBP) have been identified as key flavor compounds found in seafoods. Depending on their concentrations, they were responsible for marine or ocean flavor (shrimp/crab/fish/sea salt-like) or for phenolic/iodine/iodoform-like off-flavor. In this work a new analytical methodology was developed to determine, simultaneously, such bromophenols in fish meats, based on reversed-phased high-performance liquid chromatographic separation (RP-HPLC). The separation of bromophenols was made onto a Lichrospher 100 RP-18 column using water:acetonitrile gradient at a flow rate of 1.0 mL min−1, using absorbance detection at 286 nm, were the 2-BP, 4-BP, 2,4- and 2,6-DBP show significant absorbtivity values and at 297 nm for 2,4,6-TBP. They were separated in 20 min with a good chromatographic resolution (Rs) for the isomeric compounds: 2- and 4-BP, Rs = 1.23; 2,4- and 2,6-DBP, Rs = 1.63. The calibration curves were linear in the bromophenols concentration range of 200.0-1000 ng mL−1. Under optimized conditions, the detection limit of the HPLC method was 127 ng mL−1 for 2-BP; 179 ng mL−1 for 4-BP; 89.0 ng mL−1 for 2,4-DBP; 269 ng mL−1 for 2,6-DBP and 232 ng mL−1 for 2,4,6-TBP. This method has been applied in determination of bromophenols, isolated by combined steam distillation-solvent extraction with 2 mL of pentane/diethyl ether (6:4), from Brazilian fishes samples, collected on the Atlantic coast of Bahia (13°01′S and 38°31′W), Brazil. The concentration range determined were 0.20 ng g−1 (2-BP) to 299 ng g−1 (2,4,6-TBP). The method proposed here is rapid and suitable for simultaneous quantification of simple bromophenols in fish meat. As long as we know, it is the first analytical methodology, using RP-HPLC/UV, which was developed to determine simple bromophenols in fish meat.  相似文献   

14.
The influence of different steric and electronic properties of 2,4-; 2,5-; and 3,5- dimethylphenols (2,4-; 2,5-; and 3,5- DMP, respectively) on Ni2+-montmorillonite (Ni2+-MMT) (I) were studied. The results of X-ray diffraction show that the observed changes of the basal spacing were due to the intercalation of phenol derivatives into the interlayer space of montmorillonite. The existence of one peak at ~1,633 cm?1 in the IR spectra of sample Ni2+-MMT + 2,4-DMP (II) and Ni2+-MMT + 2,5-DMP (III) and shift of this peaks to higher frequency indicate that 2,4-DMP and 2,5-DMP exist in the interlayer space of Ni2+-MMT in the protonated form. The two bands at ~1,622 and 1,597 cm?1 in the sample Ni2+-MMT + 3,5-DMP (IV) indicate that 3,5-DMP may be also directly coordinated to Ni2+ cations. The different interactions of phenol derivatives in the silicate interlayers will be connected with different position of methyl groups on the phenol ring.  相似文献   

15.
A flow injection biosensor system was proposed for the highly sensitive detection of 2,4,6-trichlorophenol (2,4,6-TCP). The system is based on the preoxidation by ceric sulfate to the corresponding benzoquinone (2,6-dichloro-1,4-benzoquinone: 2,6-DC-1,4-BQ), which was characterized using cyclic voltammetry, hydrodynamic voltammetry, and UV-vis spectrophotometry. The laccase-based biosensor used in this analytical system responded sensitively to 2,4,6-TCP after the preoxidation by ceric sulfate. The response could be based on the bioelectrocatalytic recycling of oxidation product (2,6-DC-1,4-BQ) between laccase membrane and the electrode, because the oxidation product (2,6-DC-1,4-BQ) of 2,4,6-TCP was an electrochemically reversible redox species. The signal current was linearly related to the 2,4,6-TCP concentrations in a dynamic range of 2 nM - 2 microM; the slope and the y-intercept of the straight line were 1150 nA microM(-1) and 0.88 nA, respectively. The detection limit was 1.2 nM (S/N = 3) for a 20 microl injection. Among a variety of chlorophenols and some phenolic compounds, the only interferent was 2,4-dichlorophenol.  相似文献   

16.
Four water soluble azo dyes, 4-(isopropyl)-2-[(E)-(4-chlorophenyl)diazenyl]phenol (L 1), 4-(isopropyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L2), 4-(sec-butyl)-2-[(E)-(4-chlorophenyl) diazenyl]phenol (L 3), 4-(sec-butyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L 4), and their Cu(II) and Ni(II) complexes were synthesized and characterized using spectroscopic methods. Examination of their thermal stability revealed similar decomposition temperature of approximately 260–300°C and that they were more thermally stable than their metal complexes. Ni(II) complexes of ligands L2 and L4 were more stable than the other coordination compounds. Among the synthesized ligands, L2 and the complexes Cu(L3)2 and Ni(L4)2 showed both antimicrobial and antifungal activity. However, the other ligands and the complexes were poorly active against selected microorganisms.  相似文献   

17.
Benzotriazole UV stabilizers (BUVs) have gained popularity, due to their absorption properties in the near UV range (200–400 nm). They are used in the technology for manufacturing plastics, protective coatings, and cosmetics, to protect against the destructive influence of UV radiation. These compounds are highly resistant to biological and chemical degradation. As a result of insufficient treatment by sewage treatment plants, they accumulate in the environment and in the tissues of living organisms. BUVs have adverse effects on living organisms. This work presents the use of peracetic acid in combination with d-electron metal ions (Fe2+, Co2+), for the chemical oxidation of five UV filters from the benzotriazole group: 2-(2-hydroxy-5-methylphenyl)benzotriazole (UV-P), 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol (UV-326), 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)phenol (UV-327), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV-328), and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (UV-329). The oxidation procedure has been optimized based on the design of experiments (DoE) methodology. The oxidation of benzotriazoles follows first order kinetics. The oxidation products of each benzotriazole were investigated, and the oxidation mechanisms of the tested compounds were proposed.  相似文献   

18.
Poly(chlorophydroquinone terephthalate) is an aromatic polyester containing mainly chlorohydroquinone and terephthalate. Thermal stability of this aromatic polyester has been a problem during the processing. In order to characterize the melt reactions of this polyester, the thermal degradation of the model compound chlorohydroquinone dibenzoate was studied. The chlorohydroquinone dibenzoate was characterized by high resolution 13C-NMR. All experiments for studyng degradation of chlorohydroquinone dibenzoate were designed to test the following environmental parameters: (1) atmosphere, (2) temperature, (3) time, (4) additives, (5) container material. The analysis of the degradation products were carried out mainly using NMR; in some cases GC/MS and HPLC were also used to aid in separation and identification of the degradation products. The major degradation products produced in various experimental conditions were identified as chlorohydroquinone benzoates, hydroquinone dibenzoate, dichlorohydroquinone dibenzoate, 9-fluorenone, benzoic acid, Fries products, and hydrogen chloride  相似文献   

19.
In this study, a wall-jet flow cell with a GRC (graphite reinforced by carbon) electrode was designed for the amperometric detection of phenol and chlorophenols in liquid chromatography. The voltammetric responses of these analytes at the GRC electrodes are very similar to those at conventional glassy carbon electrodes. As the GRC electrodes were made of the same materials as commercially available mechanical pencil leads, they exhibit the advantages of low cost, simple surface renewability, lower residual current, and good electrode-to-electrode reproducibility, and thus can be used as disposable-type electrodes. Chromatographic separations of phenol, o-chlorophenol (o-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) were achieved with an ODS column using a mobile phase containing a mixture of CH3CN and H20 (40:60) containing 25 mM L-(+)tartaric acid (pH = 4.5). Amperometric detections were based on the electrochemical oxidation of these compounds around +0.9 V vs. Ag/AgCl. Under the optimized conditions, linear calibrations were obtained in a range up to 100 microM for phenol, o-CP, 2,4-DCP, 2,4,6-TCP, and 200 microM for PCP, with the correlation coefficients r2 of 0.9992, 0.9997, 0.9986, 0.9992, and 0.9968, respectively. The chromatographic detection limits for the tested analytes were obtained at pmol levels.  相似文献   

20.
Sorption of phenol, 3-cresol, 2-, 3-, 4-nitrophenols, 2,4-, 2,6-dinitrophenol, 2,4,6-trinitrophenol, and 1-naphthol by polyether- and polyester-type polyurethane foams (PUF) was investigated. The effects of sorption time, pH, phenol concentration and the structure of tested phenols and PUF were studied. The mechanism of sorption of tested compounds on foams is discussed. It is shown that the hydrophobicity (logP, octanol-water distribution constant) and pK(a) values of the compounds play an important role in the sorption process. A regression equation connecting distribution coefficient of phenols by PUF with their hydrophobicity parameter and pK(a) values were derived. Good correlation between logD and values logP and pK(a) was observed.  相似文献   

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