Methylene Blue estimation

One hundred milliliters of an aqueous solution of methylene blue contains 3.0 mg dye per liter and has an optical density (or molar absorbancy) of 0.60 at a certain wavelength. After the solution is equilibrated with 25 mg of a charcoal the supernatant has an optical density of 0.20. Estimate the specific surface area of the charcoal assuming that the molecular area of methylene blue is 197 A. ... 

Dye adsorption from solution may be used to estimate the surface area of a powdered solid. Suppose that if 3.0 g of a bone charcoal is equilibrated with 100 ml of initially 10 Af methylene blue, the final dye concentration is 0.3 x 10 Af, while if 6.0 g of bone charcoal had been used, the final concentration would have been 0.1 x Qr M. Assuming that the dye adsorption obeys the Langmuir equation, calculate the specific surface area of the bone charcoal in square meters per gram. Assume that the molecular area of methylene blue is 197 A. ... 

This enzyme is of wide occurrence in bacteria where it is concerned with the reduction of nitrate and CO2 as well as sulphur. Methods for its estimation depend on measuring some activity of hydrogenase by (a) dye reduction (benzyl viologen or methylene blue), (b) isotopic exchange and (c) evolution of molecular hydrogen. Interpretation of quantitative results is difficult due to the complex relationship between the enzyme cell structure and the particular method selected. ... 

The charge transfer kinetics of azobenzene at the mercury electrode is slower than that of methylene blue, thus the frequency interval provided by modem instra-mentation (10 < //Hz < 2000) allows variation of the electrochemical reversibility of the electrode reaction over a wide range [79]. The quasireversible maxima measured by the reduction of azobenzene in media at different pH ate shown in Fig. 2.47 in the previous Sect. 2.5.1. The position of the quasireversible maximum depends on pH hence the estimated standard rate constant obeys the following dependence A sur = (62-12pH) S- for pH < 4. These results confirm the quasite-versible maximum can be experimentally observed for a single electrode reaction by varying the frequency, as predicted by analysis in Fig. 2.75. 

Wang, L.K. Modified methylene blue method for estimating the MBAS concentration. J. Am. Water Works Assoc. 1975, 67 (7), 19-21. 

The methylene blue technique is a measure of hydrogen sulfide whereas DTNB should measure sulfide and any other organic or inorganic thiol which is present in porewater. Ideally, the bimane sulfide peak should correspond to the methylene blue concentration and the bimane total thiol concentration should correspond to the DTNB estimate. In saltmarsh cores, there was good general... 

Viability - widely used to characterize animal cell cultures - is estimated according to the ability of individual cells to catalyze a biochemical reaction, e.g. the reduction of Methylene Blue or Trypan Blue to the respective leuko-form [65,332] after staining, blue cells are distinguished microscopically from noncolored cells. This method may give a significant overestimation of cell viability because lysed or lysing dead cells are not accounted for. Flow cytometric approaches are mentioned above (see Sect. 3.1). 

Cells were exposed to drugs for 3-5 days, allowing for at least two population doublings. Cell numbers were estimated by quantification of protein content of fixed cells by methylene blue staining. Data from Ref. 38. 

There is only one example which makes use of a biopolymer, starch, imprinted with a dye [60]. Methylene Blue could be adsorbed on starch which was crosslinked with cyanuric chloride to almost 100% with respect to the concentration of theoretically available binding sites. The blank adsorbed a mere 17% under identical conditions. It is estimated that 7-8 glucose units form a single cavity for the template, somewhat reminiscent of a- or P-cyclodextrins, but shape selectivity has not been investigated. It seems remarkable but these investigations seem to have been initiated without any awareness of the earlier work on imprinting. 

A further method consists in treating a solution of chromate udth an excess of methylene white (the leuco base of methylene blue) in presence of hydrochloric acid. The methylene blue produced is then titrated with standard titanous chloride, the temperature being kept above 40° C. in order to sharpen the end-point. The whole process should be performed in an atmosphere of carbon dioxide. In applying this method to ferrochrome or chromium steel, the iron and chromium may be estimated together, the iron then being determined separately by ordinary methods and the chromium obtained by difference. The reaction may also be used colorimetrieally. ... 

Potassium perchlorate may be detected in mixtures by the methylene blue reaction (see under Potassium Chlorate). It may be estimated quantitatively by heating, as described under Potassium Nitrate, or by nitron also by precipitation as methylene blue perchlorate and titration of the excess of methylene blue with picric acid. It can also be reduced with titanous sulphate or chloride. 

Significant levels of methemoglobinemia were produced when mice were exposed to butyl nitrites via inhalation. Pretreatment of the mice with methylene blue prevented the methemoglobin formation associated with the butyl nitrite exposure. A single intravenous dose of 30 mg kg of sodium nitrite caused methemoglobinemia in dogs. The minimum lethal dose of sodium nitrite is estimated to be 150-170 mg kg in cattle and 70-75 mg kg in pigs. 

The ineidence of DHSS biodegraders among culture collection strains. The cultures harvested from nutrient agar slants were cultivated in liquid mineral media with 200 mg/1 DHSS under aeration at 28°C or 37°C. Capability of DHSS primary biodegradation of the strain was estimated as a full or a partial loss of methylene blue active substances from medium after 10 day cultivation. 

It is well known that methylene blue and other dyes are used to estimate the adsorption capacity of carbons and even to characterize their porous structure [77-80]. This implies that nonspecific dispersion adsorbate-adsorbent interactions are dominant in these systems and that the entire surface is accessible to the adsorbate. However, as Fig. 7 illustrates, the adsorption capacity depends very much on the chemistry of the carbon surface and the pH unless the uptake by this carbon is determined at a relatively high pH, the measured surface area can be underestimated by a factor of 2 (e.g., from 500 to 1000 m /g). This means that electrostatic interactions can be very important as well. 

Methylene blue reduction test This test is used to estimate the keeping quality of pasteurized milk. In principle, a measured quantity of methylene blue solution is added to 10 ml of milk in a tube. This is mixed by slow inversion, then the tube is sealed and incubated in a water bath at 37°C. A satisfactory test is given when there is no decoloration in 30 min. 

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