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Chemical Methods
Published in Jerome Greyson, Carbon, Nitrogen, and Sulfur Pollutants and Their Determination in Air and Water, 2020
As with the acid-base indicators, a redox indicator will be the color of the oxidized form if its concentration is about 10 times that of the reduced form, and vica versa. That is, the potential at which the indicator’s color will be that of the oxidized form will be given by Eox=EO+0.059n
Iron oxide/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) glassy carbon electrode as a novel label-free electrochemical microRNA-21 sensor
Published in Instrumentation Science & Technology, 2023
Cigdem Dulgerbaki, Aysegul Uygun Oksuz
In this work, we offer a novel label-free electrochemical miRNA-21 sensor in which Fe3O4 acts as the redox indicator. Fe3O4 that is directly deposited onto a glassy carbon electrode (GCE) also leads to a wide effective surface area. A conducting poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate (PEDOT:PSS) layer was coated on Fe3O4 for the immobilization of the probes. Since miRNA-21 is associated with many types of cancers, it is used as the model analyte for this study.[20] The response measurement depended upon the oxidation current of Fe3O4/PEDOT:PSS in phosphate buffer saline (PBS) utilizing cyclic voltammetry (CV). Insulation of the surface is increased by hybridization that occurs between the probes and the target miRNA and electrons transfer is prevented that decreases the redox current. Alterations in current values are found to be proportional to the concentration of miRNA-21.
Persistence of three bisphenols and other trace organics of concern in anaerobic sludge under methanogenic conditions
Published in Environmental Technology, 2021
Youn Jeong Choi, Loring F. Nies, Linda S. Lee
A 28-d batch anaerobic degradation experiment was carried out under methanogenic conditions in buffered microcosms for single and mixed bisphenol systems. One day before sampling the anaerobic sludge, a buffer solution was prepared based on the ASTM5210-92 method (ASTM D5210, 2007, detail is available in SI Table S1). Sludge was diluted with the buffer solution (1:3 v:v sludge:buffer) resulting in a slurry of ∼2000 mg dry wt./L. Buffer was added to maintain a pH range of 7.0–8.5 for the duration of the experiment. Slurry subsamples (100 mL) were transferred to 125-ml amber serum bottles. To foster the activity of methanogenic microorganisms, 50 μL of methanol as substrate was added and bottles were capped with butyl rubber aluminum crimp caps. Methylene blue (0.001 g/L) was added as a redox indicator to a small subset of microcosms to visualize an apparent redox change after which headspace was sampled to confirm methane production. The redox indicator alone is not sufficient since high sorption of methylene blue could cause the colour to no longer be evident although the redox state remained unchanged [22].
Biodegradation of petroleum hydrocarbon waste using consortia of Bacillus sp
Published in Bioremediation Journal, 2020
Wendy Snoyolo Masika, Ghaneshree Moonsamy, Prisha Mandree, Santosh Ramchuran, Rajesh Lalloo, Tukayi Kudanga
A commonly used screening method to identify oil-degrading bacteria is the DCPIP assay. 2,6-DCPIP is an indicator for oxidation of NADH to NADC carried out by oil-degrading bacteria. This assay has been used for rapid and simple isolation of hydrocarbon-degrading bacteria (El Hanafy et al. 2016). DCPIP redox indicator was prepared by adding 0.004 g of 2,6 DCPIP into 25 mL of distilled water. Attenuated bacterial cells, were prepared by autoclaving the culture at 121 °C for 15 min and used as a control. A cell suspension was prepared by growing the organisms in flasks with BH media containing diesel. The cell suspension (10 mL) and the DCPIP indicator (10 µL) was added to 50 mL falcon tube and incubated on a platform shaker at 32 °C. The reaction time was started and any color changes were noted at 10, 20, 40, and 60 min intervals. The tubes were allowed to stand overnight so that a 24-h time point could also be collected.