Electrocatalytic Oxidation and Determination of Nitrite at Multi-Walled Carbon Nanotubes Modified Electrode.

Electrocatalytic oxidation of nitrite at multi-walled carbon nanotubes (MWCNTs) modified electrode was investigated by using voltammetric techniques. The kinetic parameters such as diffusion coefficient (D), standard heterogeneous rate constant (ks) and catalytic constant (kh) were studied by chronocoulometry and chronoamperometry. The corresponding parameters for D, ks, and kh were caculated to be 3.56×10-5 cm² s-1, 6.29×10-3 cm s-1 and 7.02×10² M-1 s-1, respectively. The modified electrode was used for the determination of nitrite with a concentration range of 0.5 to 36 µM and a detection limit of 0.08 µM. The proposed method was successfully applied for the determination of nitrite in real samples of tap water and juice of pickled garlic.

Biochar Immobilizes and Degrades 2,4,6-Trichlorophenol in Soils.

Soil contamination by chlorophenol compounds, such as 2,4,6-trichlorophenol (2,4,6-TCP), is of great concern because they are environmentally persistent, are difficult to degrade, and can lead to cancer. Thus, means of degrading these compounds in situ are desperately needed. Biochar was investigated as a material to sequester, reduce downward transport, and aid in soil 2,4,6-TCP degradation. In 2 column studies, wheat straw (Triticum aestivum L.)-derived biochar (pyrolyzed at 450 °C) application to soil (up to 5% by wt) improved soil water and soil organic carbon content. Biochar reduced 2,4,6-TCP downward transport, likely attributable to improved soil water mobility and retention, allowing 2,4,6-TCP to be more easily transported and sorbed to organic functional groups on biochar, leading to enhanced degradation. The 2,4,6-TCP was rapidly degraded into a combination of benzene derivatives and low-molecular weight organic compounds in the first 2 mo following biochar application. The present study provides evidence that biochars can be used to improve environmental quality by lessening the downward transport and enhancing the degradation of organochlorine compounds such as 2,4,6-TCP. Environ Toxicol Chem 2019;38:1364-1371. © 2019 SETAC.

Colorimetric Determination of Hypochlorite Based on the Oxidative Leaching of Gold Nanorods.

Hypochlorite plays a critical role in killing microorganisms in the water. However, it can also cause cardiovascular diseases, neuron degeneration, and cancer to humans. Although traditional methods feature excellent sensitivity and reliability in detecting hypochlorite, the expensive instruments and strict determination conditions have limited their application in environmental analysis to some extent. Thus, it is necessary and urgent to propose a cheap, facile, and quick analytical assay for hypochlorite. This paper proposes a colorimetric assay for hypochlorite utilizing gold nanorods (AuNRs) as the nanoreactor and color reader. The AuNRs were acquired via a reported seed-mediated method. NaClO with strong oxidation property can cause the etching of gold from the longitudinal tips of AuNRs, which could shorten the aspect ratio of AuNRs, decrease the absorption in the UV⁻Vis spectrum and also induce the solution color changing from red to pale yellow. Thus, according to the solution color change and the absorbance of longitudinal surface plasmon resonance of AuNRs, we established the calibration curve of NaClO within 0.08 µM to 125 µM (∆Abs = 0.0547 + 0.004 CNaClO, R² = 0.9631). Compared to traditional method, we obtained the conversion formula between the concentration of residual-chlorine in tap water and the concentration of hypochlorite detected by the proposed colorimetric assay, which is Cresidual-chlorine = 0.24 CNaClO. Finally, the real application of the colorimetric assay in tap water was successfully performed, and the accuracy of the colorimetric method can reach from -6.78% to +8.53%.

Molecularly Imprinted Polymers Based Electrochemical Sensor for 2,4-Dichlorophenol Determination.

A molecularly imprinted polymers based electrochemical sensor was fabricated by electropolymerizing pyrrole on a Fe3O4 nanoparticle modified glassy carbon electrode. The sensor showed highly catalytic ability for the oxidation of 2,4-dichlorophenol (2,4-DCP). Square wave voltammetry was used for the determination of 2,4-DCP. The oxidation peak currents were proportional to the concentrations of 2,4-DCP in the range of 0.04 to 2.0 µM, with a detection limit of 0.01 µM. The proposed sensor was successfully applied for the determination of 2,4-DCP in water samples giving satisfactory recoveries.

Molecularly imprinted electrochemical sensor for the highly selective and sensitive determination of melamine.

A selective and sensitive molecularly imprinted electrochemical sensor was developed for the determination of melamine. Carbon nanotube-ionic liquid composite was used as a carrier to enhance the number of imprinted cavities and then improve the selectivity and sensitivity of the sensor. The proposed sensor showed a linear relationship with the concentration of melamine in the range of 0.4 to 9.2 µM, with a detection limit of 0.11 µM. The sensor was successfully applied to the determination of melamine in milk products with good recovery.

Electrochemical determination of Sudan I in food products using a carbon nanotube-ionic liquid composite modified electrode.

A sensitive and convenient electrochemical method was developed for the determination of Sudan I using a carbon nanotube-ionic liquid composite modified electrode with the enhancement effect of cetyltrimethyl ammonium bromide (CTAB). The modified electrode exhibited an obvious electrocatalytic activity towards the oxidation of Sudan I, and the oxidation peak current significantly increased in the presence of CTAB. The experimental parameters, such as solution pH, concentration of CTAB and accumulation time, were optimised for Sudan I determination. The oxidation peak current showed a linear relationship with the concentration of Sudan I in the range of 3.0 × 10(-8) to 3.1 × 10(-6) mol l(-1), with a detection limit of 8.0 × 10(-9) mol l(-1). The proposed method was successfully applied for the determination of Sudan I in food products of ketchup and chilli sauce.

Electrocatalytic dechlorination of chloroacetic acids on silver nanodendrites electrode.

Silver nanodendrites were successfully prepared by electrodeposition on the glassy carbon electrode. The effects of synthesis parameters such as concentrations of reagents and applied potentials on the morphology and structure of silver nanodendrites have been investigated. Electrochemical experiments showed that silver nanodendrites electrode had extraordinary electrocatalytic activity toward the dechlorination of chloroacetic acids. The electrocatalytic hydrogenolysis mechanism was the main pathway for the dechlorination of chloroacetic acids.

Nano-structured polyaniline-ionic liquid composite film coated steel wire for headspace solid-phase microextraction of organochlorine pesticides in water.

A novel nano-structured polyaniline-ionic liquid (i.e. 1-butyl-3-methylimidazolium hexafluorophosphate, BMIPF(6)) composite (BPAN) film coated steel wire was prepared by electrochemical deposition. Scanning electron microscopy images showed that the obtained porous BPAN coating consisted of nanofibers, whose diameter ranged from 50 to 80 nm. Furthermore, the novel nano-structured composite coating was very stable at relatively high temperatures (up to 350 °C) and it could be used for more 250 times without obvious decrease of the extraction efficiency. The novel BPAN coating was used for the headspace solid-phase microextraction (HS-SPME) of organochlorine pesticides (i.e. hexachlorocyolohexane, dichlorodiphenyldichloroethylene, dichlorodiphenyldichloroethane, dichlorodiphenyltrichloroethane), coupled with gas chromatography-electron capture detection (GC-ECD). The BPAN coating showed better analytical capability on the whole compared with common polyaniline (PANI) and polydimethylsiloxane (PDMS) coatings. The key parameters influencing extraction efficiency were investigated and optimized, including desorption time, stirring speed, extraction temperature, extraction time and ionic strength. The relative standard deviations (RSDs) for single fiber repeatability ranged from 2.3 to 8.7% (n=6) and the RSDs for fiber-to-fiber reproducibility (n=6) were 4.2-12.1%, respectively. The linear ranges exceeded three magnitudes with correlation coefficients above 0.99. The detection limits were 0.12-0.31 ng L(-1). The proposed method was successfully applied for the determination of organochlorine pesticides in lake water, waste water and sewage treatment plant effluent with good recoveries from 88.9 to 112.9%.

Investigation on interaction of prulifloxacin with pepsin: a spectroscopic analysis.

The interaction between prulifloxacin, a kind of new oral taking antibiotic and pepsin, a kind of enzyme in the stomach has been investigated in vitro under a simulated physiological condition by different spectroscopic methods. The intrinsic fluorescence of pepsin was strongly quenched by prulifloxacin. This effect was rationalized in terms of a static quenching procedure. The binding parameters have been evaluated by fluorescence quenching methods. The negative value of DeltaG(0) reveals that the binding process is a spontaneous process. The binding distance R between donor (pepsin) and acceptor (prulifloxacin) was obtained according to the Förster's resonance energy transfer theory and found to be 0.95 nm. The results obtained herein will be of biological significance in pharmacology and clinical medicine.