Photocatalytic degradation of fluoranthene in soil suspension by TiO2/α-FeOOH with enhanced charge transfer capacity.

Polycyclic aromatic hydrocarbons (PAHs) in soil are potentially harmful to human health. However, the use of photocatalysis technology to treat soil contaminated with PAHs remains challenging. Therefore, TiO2/α-FeOOH composite photocatalyst has been synthesized by hydrothermal method and sol-gel method and applied to photocatalytic degradation of fluoranthene in soil. The morphology, elements, crystal structure, optical properties, electrochemical characteristics, and photocatalytic activity of TiO2/α-FeOOH have been characterized. Results showed that TiO2 is tightly fixed on the surface of α-FeOOH, and TiO2/α-FeOOH had higher photocatalytic activity on photocatalytic degradation of fluoranthene in soil under simulated sunlight. The degradation efficiency of TiO2/α-FeOOH is 3.0 and 4.8 times higher than that of TiO2 and α-FeOOH, respectively. This is attributed to enhanced photocatalytic ability by enhancing the transfer capacity of electrons and holes and broadening the spectrum absorption range. The highest degradation efficiency was achieved when the pH of the soil is neutral, the ratio of water/soil is 10:1, and the dosage of catalyst is 50 mg/g. In addition, it was proved that •O2-, h+, and 1O2 are the main active substances in the photocatalysis of TiO2/α-FeOOH. The possible mechanism of a Z-type electron transfer structure was also proposed. The degradation products of fluoranthene were detected, and the degradation pathway was deduced.

Efficiency and mechanism on photocatalytic degradation of fluoranthene in soil by Z-scheme g-C3N4/α-Fe2O3 photocatalyst under simulated sunlight.

Polycyclic aromatic hydrocarbons (PAHs) in soil have potential harm on human health. However, remediation of PAH-contaminated soils through photocatalytic technology remains a challenge. Therefore, the photocatalyst g-C3N4/α-Fe2O3 was synthesized and applied to photocatalytic degradation of fluoranthene in soil. The physicochemical properties of g-C3N4/α-Fe2O3 and various degradation parameters, such as catalyst dosage, the ratio of water/soil, and initial pH, were investigated in detail. In soil slurry reaction system (water/soil=10:1, w/w), the optimal degradation efficiency on fluoranthene was 88.7% after simulated sunlight irradiation for 12 h (contaminated soil=2 g, initial fluoranthene concentration=36 mg/kg, catalyst dosage=5%, and pH=6.8), and the photocatalytic degradation followed pseudo-first-order kinetics. The degradation efficiency of g-C3N4/α-Fe2O3 was higher compared with P25. Degradation mechanism analysis showed that •O2- and h+ are the main active species in photocatalytic degradation process of fluoranthene by g-C3N4/α-Fe2O3. Coupling g-C3N4 and α-Fe2O3 enhances the interfacial charge transport capacity via Z-scheme charge transfer route and inhibits the recombination of photogenerated electrons and holes of g-C3N4 and α-Fe2O3, then significantly improves the production of active species and photocatalytic activity. Results showed that photocatalytic treatment of soil by g-C3N4/α-Fe2O3 is an effective strategy for remediation of soils contaminated by PAHs.

Gold nanoparticle-based colorimetric ELISA for quantification of ractopamine.

The work describes a gold nanoparticle-based colorimetric enzyme-linked immunosorbent assay (ELISA) for ractopamine. The ELISA is based on an indirect competitive approach. In the presence of ractopamine, gold(III) ions are oxidized by H2O2 to form red AuNPs. On the other hand, the AuNP in solution are purple-blue due to aggregation if the sample does not contain ractopamine. The absorption, best measured at 560 nm, increases linearly in the 2 to 512 ng·mL-1 ractopamine concentration range, and the detection limit is as low as 0.35 ng·mL-1 in urine. Ractopamine can also be detected visually, even in the presence of other ß-agonists and antibiotics. The results obtained by this method are consistent with those obtained by LC-MS/MS as demonstrated by analysis of sheep urine. The ELISA method described here is inexpensive, easy-to-use, and suitable for rapid screening of ractopamine in animal samples. Graphical abstract Schematic presentation of a colorimetric indirect competitive immunoassay for ractopamine. It is based on the use of catalase labeled IgG and the measurement of the absorption of red gold nanoparticles (AuNPs) that are generated by the reaction of gold ions with H2O2. In the absence of ractopamine, the solution becomes blue.

Determination of Branched-Chain Keto Acids in Serum and Muscles Using High Performance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry.

Branched-chain keto acids (BCKAs) are derivatives from the first step in the metabolism of branched-chain amino acids (BCAAs) and can provide important information on animal health and disease. Here, a simple, reliable and effective method was developed for the determination of three BCKAs (α-ketoisocaproate, α-keto-ß-methylvalerate and α-ketoisovalerate) in serum and muscle samples using high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF/MS). The samples were extracted using methanol and separated on a 1.8 µm Eclipse Plus C18 column within 10 min. The mobile phase was 10 mmol L-1 ammonium acetate aqueous solution and acetonitrile. The results showed that recoveries for the three BCKAs ranged from 78.4% to 114.3% with relative standard deviation (RSD) less than 9.7%. The limit of quantitation (LOQ) were 0.06~0.23 µmol L-1 and 0.09~0.27 nmol g-1 for serum and muscle samples, respectively. The proposed method can be applied to the determination of three BCKAs in animal serum and muscle samples.

A sensitive and semi-quantitative method for determination of multi-drug residues in animal body fluids using multiplex dipstick immunoassay.

The objective of this research was to develop a multiplex dipstick immunoassay method for the simultaneous determination of multi-veterinary drug residues, such as ß-agonists, sulfonamides, and tetracyclines in milk, urine, and serum. The multiplex dipstick assay format was based on an indirect competitive approach: Three test lines (different antigens) and one control line (goat anti-mouse IgG) were located on the strip membrane. Labeled antibodies were freeze-dried in microwells. Samples did not require pretreatment and could be directly analyzed within 10 min. Threshold levels in different sample matrices were visually estimated at 0.3-0.45 ng mL(-1) for clenbuterol; 3-4 ng mL(-1) for sulfadiazine; and 4.5-6 ng mL(-1) for tetracycline, respectively. The linear relationship between the concentrations of veterinary drug residues and the Au nanoparticles plasmon absorbance allowed quantitative determination of these veterinary drug residues. The recoveries of clenbuterol, sulfadiazine and tetracycline in spiked samples ranged from 78.4% to 112.6%, and the relative standard deviations were below 11.2%. Analysis of animal samples suggested that the proposed multiplex dipstick assay method was consistent with the LC-MS/MS method. The percentage of false results was less than or equal to 5%. Thus, the proposed multiplex dipstick assay is inexpensive, easy-to-use, and suitable for the purposes of rapid and comprehensive screening of 3 families of ß-agonists, sulfonamides and tetracyclines including 26 drugs in animal body fluids.