PubMed · 10298439
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1982. Coulometric titrators.. https://pubmed.ncbi.nlm.nih.gov/10298439/
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The development of colorimetric methods based on directly inhibiting nanozyme activity for pesticide detection has attracted considerable attention. In this study, we report a novel colorimetric sensing strategy utilizing BiO2-x/Bi2O2.75 nanosheets (BiO2-x/Bi2O2.75 NSs) with haloperoxidase (HPO)-like activity for the rapid and sensitive detection of carbosulfan (CBS) in foods. Oxygen-vacancy-rich BiO2-x/Bi2O2.75 NSs with HPO-like activity were rationally constructed. Kinetic studies revealed a remarkable Michaelis-Menten constant (Km) of 0.014 mM for I-, indicating a higher affinity for iodide ions than other reported HPO-like nanozymes, as evidenced by its lower Km. Under acidic conditions, CBS tends to be hydrolyzed to produce reductive sulfide species, which directly inhibit the iodoperoxidase-like activity of BiO2-x/Bi2O2.75 NSs, enabling selective detection with a limit of detection (LOD) of 0.18 μg/mL and a linear range of 0.20-100 μg/mL. When the concentration of interfering pesticides and substances was 5 times that of CBS, the sensor remained unaffected, exhibiting excellent stability and specificity. This work contributes to the detection of CBS in complex food matrices, bridging the application gap of HPO-like nanozymes in pesticide detection and providing a promising method for food safety detection.
An evaluation of several field kits and petroleum hydrocarbon measuring systems was conducted. The field kits were the immunoassay based EnviroGard petroleum fuels in soil test kit (EnviroGard, Millipore Canada, Mississauga, Ont., Canada), the turbidimetric based PetroFlag hydrocarbon test kit for soil (Dexsil, Hamden, CT, USA), a DR/2000 field kit (Hach Company, Loveland CO, USA) employing colorimetric test procedures and a total organic carbon (TOC) analysis instrument (Dohrmann Division, Rosemount Analytical Inc., Santa Clara, CA, USA) using oxidation principles. These procedures were compared to the traditional technique of extraction of the petroleum hydrocarbons using trichlorotrifluoroethane (Freon 113) as the solvent and subsequent infrared (IR) analysis using a portable fixed wavelength analyzer (Buck Scientific, East Norwalk, CT, USA). The EnviroGard kit was affected by the sample matrix. The soil type and the presence or lack thereof specific chemical components affected the capability to detect the petroleum hydrocarbon concentration. The PetroFlag soil test kit tended to generate results higher than the accepted concentration. The IR method was better capable of producing results similar to the expected concentration values of the prepared samples. Results indicate that the total organic carbon analysis technique evaluated is best suited for samples containing dissolved hydrocarbons in water and is not a preferred procedure for water samples containing dispersed or floating oil. At low concentrations of 10ppm and less, the TOC method and IR method have concentration values within a few parts-per-million (ppm) of each other, however, an examination of the trends in the results for all samples shows no similarity. This would indicate that the traditional extraction and infrared method and the total organic carbon method are not measuring the same parameter.Finally, the colorimetric field kit was capable of quantifying the concentration of oil in water samples within limits. The results from the oil-in-water method built into the unit at the factory were not comparable with analysis carried out by the infrared technique. With specific methods for each oil incorporated into the spectrophotometer, the comparability of data increased significantly. Results generated by the kit are dependent upon the color and amount of the oil in the sample. The kit is best suited for dark colored oils and the water samples with concentrations in the range of 10 to 85ppm by weight.
The pH indicator dye-based colorimetric method and multivariate experimental design were used for the systematic biochemical characterization of the broad-specificity enzymes haloalkane dehalogenases. Halogenated compounds for characterization of the enzymes were selected using Principal Component Analysis. The substrates were characterised by 24 physico-chemical and structural descriptors. Thirty-four substrates were selected for testing out of 194 halogenated compounds. Relative activities determined using the optimised colorimetric microplate assay were validated against the catalytic constants determined by gas chromatography. The applicability of the assay was tested with F151L, F154L and F169L mutants of the haloalkane dehalogenase from Sphingomonas paucimobilis UT26.