Determination Of P-nitrophenol Research Articles

Electrochemical Sensing Based on Metal-Organic Frameworks-Derived Carbon/Molybdenum Disulfide Composites with Superstructure and Synergistic Catalysis.

Metal-organic frameworks (MOFs)-derived nanocomposite has attracted extensive attention due to its tunable nanoscale cavities and high chemical tailorability. Herein, with the aim of developing a sensitive electrochemical sensor for p-nitrophenol, a novel MOFs-derived nanocomposite was prepared by the solvothermal method using Zr-MOFs, thiourea, and sodium molybdate as raw materials. By controlling the growth mode and reaction time, the nanohybrids displayed a superstructure composed of MOFs-derived carbon (MOFs-C) and MoS2. Scanning electron microscopy images indicated that MOFs-C/MoS2 was a flower-like porous sphere. Transmission electron microscopic images showed that the MOFs-C/MoS2 had a unique arrow target-like structure. The porous structure held great promise for the fast mass transfer into the material, while the layer-by-layer distributed carbon and MoS2 provided a great structure for the synergistic catalysis. The electrochemical oxidation of (hydroxyamino)phenol to nitrosophenol, which is an important process for the electrochemical behavior of p-nitrophenol, can be selectively catalyzed by the MOFs-C/MoS2. Therefore, the electrochemical sensor based on the MOFs-C/MoS2 material exhibited excellent analytical performance in the determination of p-nitrophenol. Using the technique of square wave voltammetry, the peak current varied quantitatively with the presence of p-nitrophenol in the wide concentration range of 0.5-500 μM. Furthermore, the electrochemical sensor exhibited good practicability in real sample analysis.

Chemical composition, cholinesterase, and α-glucosidase inhibitory activity of the essential oils of some Iranian native Salvia species

BackgroundThe plants from Salvia genus contain widely distributed species which have been used in folk medicine as well as pharmaceutical and food industries.MethodsThe chemical composition of 12 native Iranian Salvia species (14 plants) was identified using gas chromatography-mass spectrometry (GC–MS). Also, the inhibitory activity of all essential oils (EOs) was evaluated toward α-glucosidase and two types of cholinesterase (ChE) using spectrophotometric methods. The in vitro α-glucosidase inhibition assay was performed by the determination of p-nitrophenol (pNP) obtained from the enzymatic dissociation of p-nitrophenol-α-D-glucopyranoside (pNPG) as the substrate. In vitro ChE inhibitory assay was conducted based on the modified Ellman’s procedure using the measurement of 5-thio-2-nitrobenzoic acid produced from the hydrolysis of thiocholine derivatives as the substrate, in the presence of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE).ResultsTotally, 139 compounds were detected and caryophyllene oxide and trans-β-caryophyllene were the most abundant compounds in all EOs. The yield of EOs extracted from the plants were also calculated in the range of 0.06 to 0.96% w/w. Herein, α-glucosidase inhibitory activity of 8 EOs was reported for the first time and among all, S. spinosa L. was found to be the most potent inhibitor (90.5 inhibition at 500 μg/mL). Also, the ChE inhibitory activity of 8 species was reported for the first time and our results showed that the BChE inhibitory effect of all EOs was more potent than that of AChE. The ChE inhibition assay indicated that S. mirzayanii Rech.f. & Esfand. collected from Shiraz was the most potent inhibitor (72.68% and 40.6% at the concentration of 500 μg/mL, toward AChE and BChE, respectively).ConclusionsIt seems that native Salvia species of Iran could be considered in the development of anti-diabetic and anti-Alzheimer's disease supplements.

Biosensor Method for Simple and Fast Determination of P-Nitrophenol in Soil

Biosensor Method for Simple and Fast Determination of P-Nitrophenol in Soil

基于碳量子点内滤作用测定水样中对硝基苯酚

基于碳量子点内滤作用测定水样中对硝基苯酚

Electrochemical evaluation of intermediate reduction of p-nitrophenol to nitroso derivative at palladium-phosphate electrode

ABSTRACT A novel voltammetric sensor for the determination of p-nitrophenol has been developed using carbon paste electrode (CPE) modified by metallic palladium (Pd) supported onto natural phosphate (NP). The proposed protocol demonstrates the successful application of palladium compounds in the electrochemical determination of p-nitrophenol (p-NP) in acetate buffer (pH 4.7). Indeed, the palladium displayed a strong catalytic action towards p-nitrophenol reduction. Electrochemical methods including square wave voltammetry (SWV) and chronoamperometry have been used to evaluate the electrochemical behaviour of the palladium towards the catalytic reduction of p-NP. In addition, the proposed electrode was able to catalyse and visualise the intermediate reaction of the nitro group reduction to nitroso group.

基于MoS2量子点荧光内滤作用测定环境水样中对硝基苯酚

基于MoS2量子点荧光内滤作用测定环境水样中对硝基苯酚

Synthesis of Molecularly Imprinted Polymers Coated on Silica Nanoparticles for Removal of P-Nitrophenol from Crude Pharmaceuticals

This paper describes the preparation of molecularly imprinted polymer (MIP) layer-coated silica nanoparticles for separation and determination of p-nitrophenol from active pharmaceutical ingredients. A new MIP was synthesized using p-nitrophenol, methacrylic acid (functional monomer), MPTS (chemically modifier), silica nanoparticles, ethylene glycol dimethacrylate (cross-linker), 2,2′-azobisisobutironitril (intiator) and toluene – acetonitrile (porogenic solvent). The surface of silica nanoparticles (Si–NP) was modified by reaction with 3-)methacryloxy)propyltrimethoxylsilane. Then, MIP coated on silica nanoparticles was synthesized by copolymerization of the vinyl end groups with functional monomer, cross-linking agent, initiator, and template molecule and these particles were used for solid-phase extraction of p-nitrophenol. To compare the performance of this MIP, a control polymer or non-imprinted polymer (NIP) was prepared using the same method and same material without the template molecule. The synthesized polymers were characterized by FT-IR spectroscopy, XRD, and SEM techniques. Parameters such as adsorption time, solution pH, and type of eluent for the elution of impurities from MIP were optimized. Selectivity of the MIP for the absorption of p-nitrophenol was investigated through adsorption experiments and the results were compared with the adsorption of impurities by NIP.

Microchip-based Cloud Point Extraction System and Its Application to Determination of p -Nitrophenol in Water Samples

A method was developed by integrating cloud point extraction into a microchip.Complicated operations in conventional cloud point extraction process,such as mixing,heating,and centrifugation,were avoided.The system was composed of two poly( methyl methacrylate)( PMMA) plates with the microchannels sandwiched in between.The collection material was integrated in the microchip to entrap the surfactant phase,and then the entrapped surfactant phase was eluated for sequent UV-Vis spectrophotometric determinations.The analytical performances of the microchip-based cloud point extraction system were evaluated with p-nitrophenol as a model test analyte.Effects of various parameters were optimized.The optimal conditions were as follows: sample flow rate of 0.15 mL/min,sample volume of 0.5 mL,sample pH of 11.0,surfactant concentration of 1.5%,methanol-water with a volume ratio of 70 ∶ 30 as the eluent,eluent flow rate of0.14 mL/min,and eluent volume of 0.7 mL.Within the linear range of 0.25-12 mg/L,the limit of detection was determined as 0.075 mg/L.The intra-day and inter-day relative standard deviations were 2.8%and 6.4%,respectively.When applied to the determination of p-nitrophenol in environmental water samples,the recovery values were in the range of 90.8%-102.7%.

Enhanced Indirect Fluorescence Detection of p-Nitrophenol, 2,4-Dinitrophenol and Trinitrophenol by Micellar Electrokinetic Capillary Chromatography with In-column Optical-fiber LED-induced Fluorescence Detection

Enhanced indirect fluorescence detection with in-column optical-fiber LED-induced fluorescence (LED-IF) detection has been developed for the simultaneous separation and determination of p-nitrophenol, 2,4-dinitrophenol and trinitrophenol. The instrumental set-up is simple, cost-effective and the detection method is stable. Different experimental parameters have been studied. The optimum conditions were determined as: running buffer (pH 9.1) composed of 10 mM borate, 80 mM sodium dodecylsulfate and 0.18 µM fluorescein (as a background reagent); applied voltage of 15 kV; working temperature of 25.0 °C. The limits of detection (S/N = 3) were 11, 18 and 16 µM for p-nitrophenol, 2,4-dinitrophenol and trinitrophenol, respectively. The nitrophenols were completely separated in 13 min and the number of theoretical plates for p-nitrophenol, 2,4-dinitrophenol and trinitrophenol were 8.1 × 10(6), 6.5 × 10(6) and 8.4 × 10(6), respectively. The RSDs (n = 6) for the migration time and the peak area were better than 0.85 and 0.91%, respectively. Our proposed method possesses the advantages of rapidness and good separation efficiency.

Environmental monitoring of phenolic pollutants in water by cloud point extraction prior to micellar electrokinetic chromatography

Many aromatic compounds can be found in the environment as a result of anthropogenic activities and some of them are highly toxic. The need to determine low concentrations of pollutants requires analytical methods with high sensitivity, selectivity, and resolution for application to soil, sediment, water, and other environmental samples. Complex sample preparation involving analyte isolation and enrichment is generally necessary before the final analysis. The present paper outlines a novel, simple, low-cost, and environmentally friendly method for the simultaneous determination of p-nitrophenol (PNP), p-aminophenol (PAP), and hydroquinone (HQ) by micellar electrokinetic capillary chromatography after preconcentration by cloud point extraction. Enrichment factors of 180 to 200 were achieved. The limits of detection of the analytes for the preconcentration of 50-ml sample volume were 0.10 microg L(-1) for PNP, 0.20 microg L(-1) for PAP, and 0.16 microg L(-1) for HQ. The optimized procedure was applied to the determination of phenolic pollutants in natural waters from San Luis, Argentina.

Changing the Electrophoretic Mobility of Phenols Using Ionenes as Additives in the Buffer Electrolyte

Water-soluble polymers of the ionene class with increased hydrophobicity (2-10-, 6-9-, and 3-X-ionenes) are used as modifiers in capillary electrophoresis in the determination of p-nitrophenol, phenol, and resorcinol. It is shown that 2-10-ionene provides the highest selectivity of phenol separation among all of the selected ionenes. The application of this polymer increases the selectivity of determination compared to commercially available 3-6-ionene (Polybrene) and poly(diallyldimethylammonium chloride). Under optimum conditions (a phosphate buffer solution, pH 11, U = –15 kV, l cap = 50 cm), the separation efficiency of more than 40000 theoretical plates per capillary has been achieved with an analysis time of about 8 min. Using a stacking procedure, the efficiency of more than 250000 theoretical plates per capillary has been achieved. Changes have been introduced into the design of the capillary cartridge of a Kapel'-103R instrument. As a result, it has been possible to increase the field strength up to 1180 V/cm and, thus, to decrease the analysis time down to 2.5 min. The sensitivity of the instrument is mainly determined by the quality of the equipment used. The limits of detection of phenols are about 40 μg/mL for a Kapel'-103R instrument and 0.05–0.1 μg/mL for a Hewlett-Packard HP3D CE.

Effect of Long-Term Ethanol Pretreatment on the Metabolism of Dichloromethane to Carbon Monoxide in Rats

The present study investigates the influence of long-term ethanol (ETOH) treatment of rats [10% (v/v) for 4, 12, and 36 weeks] on the metabolism of DCM after its oral and inhalative uptake to CO. Biotransformation of DCM to CO as measured by carboxyhemoglobin (COHb) formation was stimulated after long-term ETOH treatment in rats. A single oral dose of DCM (6.2 mmol/kg body mass) caused a significant increase of COHb, the maximum of about 9% occurring approximately 6 hr after DCM administration. In comparison to this control, in the blood of rats pretreated with ETOH (10% v/v) for 4, 12, and 36 weeks COHb values of 18, 17, and 13%, respectively, were measured. Long-term ETOH treatment followed by inhalation of 100, 500, and 2500 ppm DCM for 4 hr stimulated the formation of COHb, compared to controls. The elevation of COHb level was accompanied by decreased concentrations of DCM in the blood. The reason for the elevated biotransformation of DCM was ascertained by means of the determination ofp-nitrophenol and aniline hydroxylation in liver microsomes of rats after long-term ETOH treatment to be an increase in cytochrome P450-dependent enzyme activities.

Determination of Enzymatic Activities Based on an Optical Flow-Through p-Nitrophenol Sensor

Abstract An optical flow-through biosensor based on the transient retention of p-nitrophenol on an ion-exchange support packed in the flow cell is presented. The approach was applied to the determination of the activity of some enzymes which catalyze the conversion of p-nitrophenyl-derivatives into p-nitrophenol. The method was first developed for determination of p-nitrophenol yielding a linear range between 0.1–5 μg/mL (r2 = 0.9922, r.s.d.% less than 2.5), then, it was also applied to the determination of β-D-glucuronidase activity in serum, with a linear range between 0.1–20 U/L (r2 = 0.9976, r.s.d.% less than 3.0), and a sampling frequency of 20 h−1. The application of the method to the determination of the enzyme activity in serum samples provided results consistent with those obtained by a conventional method and recoveries within 95–104%.

Determination of p-nitrophenol in serum and urine by enzymatic and non-enzymatic conjugate hydrolysis and HPLC. Application after parathion intoxication.

In connection with the toxicologic analysis of a number of parathion intoxications a method for determination of free and conjugated forms of p-nitrophenol (p-NP) as the main metabolite of parathion in blood and urine was established. Quantification of conjugates is based on their hydrolysis followed by detection of p-NP using a sensitive HPLC method. Hydrolysis of both p-NP-glucuronide and p-NP-sulfate is performed by specific enzymes and also by mineral acid, the latter is also found to be highly selective under definite conditions. The two hydrolysis methods applied showed a good correlation. The levels of free and conjugated p-NP in series of blood and urine samples were established after survival from two parathion intoxications. The individual levels of p-NP-sulfate and p-NP-glucuronide in both cases are discussed in respect of results made by other authors in this field.

Determination of p-nitrophenol in human urine

A rapid, sensitive gas chromatographic method for the determination of PNP in urine at levels as low as 50 ppb is described. The method involves an acid hydrolysis, cleanup, selective extraction, and on-column formation of the trimethylsilyl ether derivative of PNP.

Evaluation of exposure to nitrobenzene. Absorption of nitrobenzene vapour through lungs and excretion of p-nitrophenol in urine.

In order to obtain a quantitative test for measuring exposure to nitrobenzene, experiments on men were done, in which nitrobenzene vapours (5 to 30 μg./l.) were absorbed into the lungs only. During an exposure of six hours the retention of nitrobenzene in the lungs diminished from approximately 87 to 73%. p-Aminophenol was not detected in the urine by the method used. Another metabolite, p-nitrophenol, was estimated in the urine of the exposed subjects; the quantities present represented about 13% of the inhaled dose of nitrobenzene. It was found that the determination of p-nitrophenol in urine could be used as a quantitative test when a single exposure to nitrobenzene occurred with a precision of approximately ± 8 mg. nitrobenzene. p-Nitrophenol is excreted in urine very slowly and therefore it may accumulate in the body. To evaluate the results of the proposed test in the case of a repeated exposure further investigations are necessary.

The determination of p-nitrophenol and p-nitrophenyl-O-S-diethyl thiophosphate in parathion

The determination of p-nitrophenol and p-nitrophenyl-O-S-diethyl thiophosphate in parathion