Determination Of 4-nitrophenol Research Articles

Biosynthesis of CuFe2O4@Ag hybrid nanocomposite: Ultrasensitive detection and catalytic reduction of 4-nitrophenol

Due to the dearth of extremely capable, sensitive, and stable catalysts, the efficient detection and catalytic removal of 4-nitrophenol (4-NP) in industrial wastewater remains a serious challenge. The detection and determination of 4-nitrophenol (4-NP) presence in the environment is a matter of paramount importance because it is a high-priority hazardous pollutant that can affect people, animals, and plants. Here, we present a promising and economically viable green synthetic route for fabricating CuFe2O4 and CuFe2O4@Ag hybrid nanocomposites from the leaf extract of Senna didymobotrya. The UV–Vis, FTIR, XRD, FE-SEM, EDXA, BET and VSM analysis were performed to characterize the synthesis of CuFe2O4@Ag nanocomposite. To evaluate the electrocatalytic capacity of CuFe2O4@Ag, electrochemical sensing stratergy was performed with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The modified CuFe2O4@Ag glassy carbon electrode (GCE) (CuFe2O4@Ag/GCE) demonstrated a linear response in the range of 0.01-15 μg/ml (71 nm-107 μM) and the ability to detect 4-NP at low concentration (0.006 μg/ml (43 nM)). Due to the increased surface area of CuFe2O4@Ag/GCE by ̴ 1.5-fold, a greater cathodic current response (-16 μA/cm2) at a low potential of -0.81 V was observed compared to CuFe2O4/GCE alone for the detection of 4-NP. Additonally, CuFe2O4@Ag showed excellent reduction ability towards 4-NP using NaBH4 with an efficiency of 96.4 % which was higher than the CuFe2O4 (only 87.3 %) in 12 min due to the synergistic relationship among Ag NPs and CuFe2O4 nanostructures. The outcomes from this study shows that the bi-functional electrocatalyst holds vast potential for environmental remediation.

Mn-Fe3O4 nanoparticles anchored on the urushiol functionalized 3D-graphene for the electrochemical detection of 4-nitrophenol

Preparation of highly active and cost-effective electrode materials is of great interest in electrochemical detection. In this study, a simple urushiol-templated solvothermal method combined with calcination was proposed to fabricate N-doped three-dimensional graphene (3D-G) with Mn-doped Fe3O4 nanoparticles loaded on the surface (Mn-Fe3O4/3D-G). Because of the large active surface area, porous channel and high loading ratio of Mn-Fe3O4 nanoparticles, as-prepared Mn-Fe3O4/3D-G sensor showed high activity on the determination of 4-nitrophenol (4-NP), which are much improved from the control un-modified samples. The wide linear concentration range (5–100 μM), low detection limit (19 nM) and satisfactory recovery of 4-NP in various water samples (98.38–100.41%) indicated that the Mn-Fe3O4/3D-G electrode can be potentially used for real-world applications. This study gives a simple but meaningful strategy for constructing transition metal oxide/graphene composite materials with high electrocatalytic activity.

Anodic differential pulse voltammetric determination of 2-nitrophenol at a non-traditional carbon film composite electrode

Abstract A new method was developed for the determination of 2-nitrophenol (2-NP) by differential pulse voltammetry (DPV) employing the anodic oxidation of the present hydroxyl group using a non-traditional carbon film composite electrode (CFCE) based on a microcrystalline natural graphite-polystyrene composite film. Britton-Robinson (BR) buffer of pH 6.0 was found to be an optimal supporting electrolyte. Cleaning regeneration potentials Ein = +1300 mV and Efin = 0 mV had to be applied before each measurement to get rid of problems connected with electrode passivation. Linear calibration curves were obtained in the concentration range from 0.2 to 10 μmol L−1 of 2-NP for both tested matrices (deionized and drinking water). Limit of quantification (LOQ) for DPV at the CFCE was found to be 0.2 μmol L−1 and 0.1 μmol L−1 for deionized and drinking water, respectively.

Simultaneous voltammetric determination of nitrophenol isomers based on a modified electrode by silver nanowires and poly-L-arginine

ABSTRACT A novel-modified electrode was constructed for simultaneous determination of 4-nitrophenol (4NP) and 2-nitrophenol (2NP). A glassy carbon electrode (GCE) was modified by silver nanowires and poly-L-arginine (poly-L-Arg/AgNWs/GCE). Compared to GCE, the modified electrode showed more sensitive peak currents for the oxidation and reduction of nitrophenol isomers. Well-resolved oxidation peaks were appeared in cyclic voltammetry at +0.08 V (4NP) and at −0.32 V (2NP). Under optimised experimental conditions, calibration curves were obtained for the two isomers. The linear concentration range was 1.0–210 μM for 4NP, and 3.0–210 μM for 2NP, with limits of detection (LOD) as 0.9 μM and 1.0 μM, respectively. The application of the method to simultaneous determination of nitrophenol isomers in tap and river water samples was satisfactory. Low concentrations of 2NP and 4NP were spiked to the real samples and their recoveries were calculated by the proposed method. The recoveries in tap and river water samples were found to be 96.92% and 104.98% for 4NP (2.0 μM), and 95.31 and 103.88 for 2NP (3.0 μM), respectively. Relative standard deviations were calculated for three replicate measurements of the spiked nitrophenols which were between 3.50% and 4.73%. The sensor showed a long-term stability of more than 1 month.

Dispersed copper nanoparticles promote the electron mobility of nitrogen-rich graphitized carbon aerogel for electrochemical determination of 4-nitrophenol.

An electrochemical method was designed for the determination and simultaneous reduction of4-nitrophenol (4-NP). A nitrogen-rich carbon aerogel was synthesized from the precursor of phenol, formaldehyde and melamine. Then, copper nanoparticles were embedded into the aerogel, and the resulting material was used to modify a glassy carbon electrode (GCE), which displayed excellent electrocatalytic activity. Sensitive determination of 4-NP by cyclic voltammetry in 0.5M sulfuric acid was accomplished. Among the various compositions of Cux@NC, the electrode modified with Cu3@NC showed the strongest reduction peak, typically at a potential of -0.30V vs. reversible hydrogen electrode (RHE). A further study shows the cyclic voltammetry potential range to extend from -0.46 to +0.44V (vs. RHE) at a scan rate of 100mVs-1. Differential pulse voltammetric determination of 4-NP gave a lower detection limit of 53nM and a current sensitivity of 0.7μAμM-1cm-2. The method was applied to the determination of 4-NP in spiked water samples, with comparable results of HPLC. The excellent performance was attributed to the highly graphitized structure of the aerogel with its large surface area and small pore size, and the presence of Cu-N structures as active sites. Graphical abstractSchematic representation of electrochemical determination and reduction of 4-nitrophenol under the glassy carbon electrode modified with highly dispersed Cu nanoparticles embedded on nitrogen-rich carbon aerogel. W:working electrode; R:reference electrode; C:counter electrode). Left: copper nanoparticles embedded in an aerogel.

Preparation of metal-organic framework MIL-101(Cr) incorporated polymer monolithic column for on-line solid-phase extraction of phenols

A metal-organic framework (MOF) MIL-101(Cr) incorporated polymer monolithic column was prepared, and a method was developed for the determination of 4-nitrophenol, 3-methylphenol, 2-nitrophenol and 2,4-dichlorophenol in water samples by on-line solid phase extraction (SPE) coupled with high performance liquid chromatography (HPLC). Effects of sample solution pH values, sample loading time, sample loading flow rates and desorption time on the on-line SPE of phenols were investigated. Under the optimized extraction conditions, large enhancement factors, wide linearity range, good precisions and low limits of detection were achieved. The results showed that the incorporation of MOFs in porous polymer monolith to fabricate MOF-incorporated monolith is one of the best ways to promote and expand the application of MOFs in on-line SPE.

Determination of 4-nitrophenol in Water using Free-Standing Cu Nanowire Electrode

Determination of 4-nitrophenol in Water using Free-Standing Cu Nanowire Electrode

Micro volume voltammetric determination of 4-nitrophenol in dimethyl sulfoxide at a glassy carbon electrode

This study presents a miniaturized instrumentation for the determination of a model electrochemically reducible compound, 4-nitrophenol, in micro volumes of dimethyl sulfoxide at the glassy carbon electrode. Several working configurations of a three-electrode system and different constructions of reference electrodes are described. Moreover, the problem of the removal of oxygen (which is rather difficult in micro volumes) complicating the determination by differential pulse voltammetry, especially in a cathodic potential range was successfully solved. It has been found that the interference of oxygen can be partly eliminated by square wave voltammetry which is less sensitive to the presence of oxygen in the sample. Special apparatus capable of removing dissolved oxygen from 20 mm3 of solution was also constructed and tested. It was verified that 4-nitrophenol can be determined in micro volumes of dimethyl sulfoxide by square wave voltammetry in the presence of dissolved oxygen (limit of quantification LOQ = 6.0 µmol dm−3) and by differential pulse voltammetry after the removal of dissolved oxygen (LOQ = 2.4 µmol dm−3). Both those methods are comparable with the determination in a macro volume (5.0 cm3), which has LOQ = 1.3 µmol dm−3.

Molecularly Imprinted Polymer Preconcentration and Flow Injection Amperometric Determination of 4-Nitrophenol in Water

Molecularly imprinted polymers are reported as selective solid-phase extraction sorbents for the preconcentration of 4-nitrophenol in water. A graphite pencil electrode modified with multiwalled carbon nanotubes provided good sensitivity and excellent anti-fouling properties for flow injection amperometry. Solid-phase extraction cartridges containing 100 mg of imprinted polymers with a sample volume of 50 mL resulted in a preconcentration factor of 97.7, which allowed determination of 4-nitrophenol at the maximum level permitted by the United States Environmental Protection Agency (60 µg L−1). A linear dynamic range of 5–300 µg L−1 for 4-nitrophenol was obtained with a limit of detection of 1.5 µg L−1. The method was employed for the determination of 4-nitrophenol in water.

Oxidative and Reductive Detection Modes for Determination of Nitrophenols by High-Performance Liquid Chromatography with Amperometric Detection at a Boron Doped Diamond Electrode

ABSTRACTHigh performance liquid chromatography with electrochemical detection using a wall-jet arrangement with a working boron-doped diamond film electrode was used for the determination of 2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol using reduction and oxidation modes. The optimal conditions for separation at a C18 reverse phase column (125 × 4 millimeters, 5 micrometers) and amperometric detection of these nitrophenols were determined. Acetate buffer (0.05 mole per liter pH 4.7/methanol 58/42, v/v) was chosen as the mobile phase for cathodic detection at the potential of −1.2 volts. The linear dynamic range was 2 × 10−6 to 1 × 10−4 mole per liter and the limits of detection were from 0.7 to 1.2 micromole per liter. For anodic detection, the mobile phase was 0.05 mole per liter phosphate buffer pH 6.75/methanol (65/35, v/v) at a detection potential of +1.3 volts. The linear dynamic range was from 2 × 10−6 to 1 × 10−4 mole per liter with limits of detection from 0.6 to 1.5 micromoles per liter. The method was successfully employed for direct determination of nitrophenols in drinking and river water with limits of detection between 0.7 and 1.8 micromoles per liter.

Determination of 4-nitrophenol at Iron Phthalocyanine Decorated Graphene Nanosheets Film Modified Electrode

Determination of 4-nitrophenol at Iron Phthalocyanine Decorated Graphene Nanosheets Film Modified Electrode

Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop with Central Composite Design for the Determination of Nitrophenols Using High-Performance Liquid Chromatography

A simple and practical pre-concentration method, dispersive liquid-liquid microextraction based on solidification of a floating organic drop (DLLME-SFO) technique, was proposed for the determination of 4-nitrophenol and 2-nitrophenol in water samples. The effective experimental parameters on the extraction efficiency such as extraction solvent volume, dispersive solvent volume, and pH were studied using the response surface methodology. Under the optimum experimental conditions, the pre-concentration factors of 116 and 100 for 2-nitrophenol and 4-nitrophenol were obtained, respectively. The calibration curves were linear in the range of 5-150 µg L−1 with the detection limit of 1.70 µg L−1. The proposed method was successfully applied to the determination of nitrophenols in water samples.

Very sensitive differential pulse adsorptive stripping voltammetric determination of 4-nitrophenol at poly (diphenylamine)/multi-walled carbon nanotube-β-cyclodextrin-modified glassy carbon electrode

In this work, a glassy carbon electrode (GCE) modified with poly (diphenylamine)/multi-walled carbon nanotubes-β-cyclodextrin (PDPA/MWCNT-β-CD) film was constructed and used for the determination of 4-nitrophenol (4-NP). Diphenylamine was successfully electropolymerised onto MWCNT-β-CD-modified GCE by cyclic voltammetry in monomer solution and 5 mol L−1 H2SO4. The surface morphology of PDPA/MWCNT-β-CD film was characterised using scanning electron microscopy and electrochemical impedance spectroscopy. After adsorption of 4-NP on PDPA/MWCNT-β-CD at 0.2 V for 150 s, it showed a well-defined reduction peak in phosphate buffer solution at pH = 7. The PDPA/MWCNT-β-CD film enhanced the reduction peak current due to the complex formation between β-CD and 4-NP, presence of conductive polymer film as electron transfer mediator and also ability of MWCNTs for strong adsorptive and catalytic effect. Peak current increased linearly with 4-NP concentration in the range of 0.1 to 13.9 µg L−1. The detection limit was obtained as 0.02 µg L−1, which is better than other reported detection limits for the determination of 4-NP. The results showed that modified electrode has good sensitivity and selectivity. This sensor was used for the determination of 4-NP in water samples.

Determination of 2-Nitrophenol by Electrochemical Synthesized Mg/Fe Layered Double Hydroxide Sensor

Determination of 2-Nitrophenol by Electrochemical Synthesized Mg/Fe Layered Double Hydroxide Sensor

Amperometric method for rapid detection of Escherichia coli by flow injection analysis using a bismuth nano-film modified glassy carbon electrode

A new method for rapid detection of Escherichia coli ( E. coli) was developed by flow injection analysis (FIA) using bismuth nano-film modified glassy carbon electrode (BiNFE) in this paper. The method depended on a good marker β- d-glucuronidase which is found in E. coli strains. β- d-Glucuronidase was produced by the induction of methyl-β- d-glucuronide sodium (MetGlu), then released from E. coli cells through the permeabilization of cell membrane caused by polymyxin B nonapeptide and lysozyme. The released β- d-glucuronidase could catalyze the hydrolysis of the substrate 4-nitrophenyl β- d-glucuronide (PNPG) in the culture medium to produce 4-nitrophenol. Since 4-nitrophenol is electroactive and its quantity is proportional to the concentration of E. coli, E. coli could be determined by electroanalysis of 4-nitrophenol. The BiNFE was fabricated by an electrodeposition of metallic bismuth onto a glassy carbon electrode, which showed a high sensitivity in determination of 4-nitrophenol when used in conjunction with FIA system. Experimental results showed that the amplified response current of 4-nitrophenol obtained at the BiNFE was linear with the concentration of E. coli ranging from 1.5 × 10 2 to 1.0 × 10 6 cfu/ml, the detection limit of this method for E. coli is 100 cfu/ml, and the complete assay was performed in 3 h.

Solid-phase microextraction of phenol compounds using a fused-silica fiber coated with beta-cyclodextrin-bonded silica particles.

A novel solid-phase microextraction (SPME) fiber was prepared by coating an HPLC beta-cyclodextrin bonded silica stationary phase (CDS) on the surface of a fused-silica fiber. The fiber was evaluated for the determination of five phenol compounds (phenol, 2,4-dimethylphenol, 4-nitrophenol, 3-chlorophenol, 4-methylphenol). Compared with commercially available polymer coatings, the CDS coating showed high sensitivity and fast velocity of mass transfer for phenol compounds because of its porous structure and a unique molecular structure of beta-cyclodextrin. In addition, the CDS coating was proved to be very stable at a relatively high temperature (up to 300 degrees C). The method was suitable for the determination of phenol compounds in aqueous samples. The determination of 4-nitrophenol in soil by microwave-assisted extraction (MAE) coupled to solid-phase microextraction was also investigated.

Determination of 2-Nitrophenol, 4-Nitrophenol, 2-Methoxy-5-nitrophenol, and 2,4-Dinitrophenol by Differential Pulse Voltammetry and Adsorptive Stripping Voltammetry

The behaviour of the title substances, which are components of the commercial plant growth stimulator Sviton, in differential pulse voltammetry at a hanging mercury drop electrode was studied and the optimum conditions were established for their quantitation over the concentration region of 1 .10-7 to 1 .10-5 mol l-1. Additional decrease in the limit of determination was achieved in adsorptive stripping voltammetry, by which 4-nitrophenol and 2-nitrophenol can be determined within the concentration regions of 2 .10-10 to 1 .10-7 and 2 .10-8 to 1. 10-7 mol l-1, respectively, and 2,4-dinitrophenol and 2-methoxy-5-nitrophenol within the region of 2 .10-9 to 1 .10-7 mol l-1.

Mechanized System for Liquid Chromatographic Determination of 4-Nitrophenol and Some Other Phenolic Pesticide Metabolites in Urine

Abstract Protecting the health of workers who are exposed to pesticides is of concern. One helpful approach is to periodically analyze the urine of such workers for metabolites of those pesticides encountered in the working environment. Therefore, an analytical system for several urinary pesticide metabolites, which incorporates a high degree of mechanization, has been developed. Urine samples (ca 8 ml) are placed in a sampler module. An acid hydrolysis step, a steam distillation step, and a combined liquid chromatographic separation and UV absorption determinative step are performed automatically, except for the need for an operator to turn a loop valve injector for the liquid chroma tograph at an exact time after the start of sampling each sample. At the slowest rate, a sample is analyzed every 24 min with a lower limit of detectability from 1 to 2 ppm added 4-nitrophenol in urine. Acid hydrolysis is included to cleave urinary conjugates of the analyte(s) of metabolic origin; steam distillation provides considerable cleanup. The method, with minor adjustment of chromatographic conditions, also responds to <5 ppm each of the other phenols derivable from the below-named (and some other) pesticides. Alternative conditions permit detection of <1 ppm 1-naphthol. Exact limits lower than the numerical values stated have not been determined. The method has the capability for assessing human exposure primarily to parathion, paraoxon, methyl parathion, and EPN, but also to carbaryl, Landrin, 2-phenyIphenol, bromophos, bromophos-ethyl, iodofenphos, 2,4,5-trichlorophenol, 2,4,5-trichlorophenoxyacetic acid, fenoprop, trichloronat, and fenchlorphos. The applicability of the method was demonstrated by fortifying urine with phenolic standards corresponding to the phenolic moieties as metabolically produced from these pesticides or to the phenolic parent pesticide.

Simultaneous determination of 4-nitroanisole, 4-nitrophenol, and 4-nitrocatechol by phase-sensitive ac polarography.

Phase-sensitive ac polarography was applied to the simultaneous quantitative determination of 4-nitroanisole, 4-nitrophenol, and 4-nitrocatechol in alkaline solutions. Certain experimental precautions are necessary to determine each compound in the presence of the other two. Thus, 4-nitrocatechol is determined indirectly by forming a yellow ratio chelate with cupric ions, wheras 4-nitroansole is determined directly by the reduction waves of the nitro group. For the determination of 4-nitrophenol, the interferency by the simultaneously present 4-nitrocatechol must be eliminated by masking it by the addition of magnesium ions. The method described permits a qualitative and quantitative analysis of all three compounds in one solution since linear calibration curves are obtained.