Bromocresol green preparation

A sharper colour change is obtained with the mixed indicator methyl red-bromocresol green (prepared from 1 part of 0.2 per cent methyl red in ethanol and 3 parts of 0.1 per cent bromocresol green in ethanol). 

Cavrini et al. [32] reported the development of a colorimetric method for the determination of miconazole nitrate in pharmaceutical preparation. The method is based on the formation of a yellow complex between the drug and bromocresol green. The absorption peak of this complex, extracted by chloroform over the pH 2—4 range, was at 424 nm, and linear response was obtained from 3—13 pg/mL. The molar absorptivity of the complex in chloroform was 1.845 x 104. This procedure is suitable for the analysis of miconazole nitrate in commercial dosage forms. 

Buffered Indicator Solution Prepare a mixture consisting of 700 mL of 0.1 M citric acid (anhydrous, reagent grade), 200 mL of 0.2 M disodium phosphate, and 50 mL each of 0.2% bromophenol blue and of 0.2% bromocresol green in spectrograde methanol. 

Mixed Indicator Solution Prepare separate 0.1% solutions of bromocresol green in methanol and the sodium salt of methyl red in water. Mix 5 parts by volume of the bromocresol green solution with one part of the methyl red solution. 

A 1 to 1.5 A/ solution of methylamine in benzene is prepared by leading methylamine (from a lecture bottle) through 100 mL of dry benzene during about 30 min. The actual concentration of the amine is determined by acid-base titration, using dilute hydrochloric acid and bromocresol green as indicator. 

The adsorbent was prepared by adding methanol to silicic acid, in an amount which would not make the adsorbent gummy and sticky. An indicator, bromocresol green, was added along with the alcohol. The column was packed with this adsorbent in the usual fashion, and a solution containing 10 mg of each acid from C5 to Cio was added to the column in 2 ml of isooctane. The column was developed with isooctane, and the zones on the column appeared yellow because of the indicator. The fractions were collected as they passed from the column, and the acids were recovered in pure form with better than 95 per cent recovery. 

Preparation, (a) Place 12.8 g. of trichloroacetic acid in a 125-ml. Erlenmeyer with a side arm and, with cooling in an ice bath, pour in about nine tenths of an ice cold solution of 3.2 g. of sodium hydroxide pellets in 12 ml. of water. Add a drop of 0.04% Bromocresol Green solution to produce a faint yellow color, and with a capillary dropping tube titrate the solution to an end point where a single drop produces a change from yellow to blue. Close the flask with a rubber stopper, mount it within the rings of a steam bath and wrap a towel around it for maximal heat, connect it to the suction pump, and turn on the water at full speed. The evaporation needs no attention and can be completed in 15-20 minutes. The weight of dry powder is close to the theory (14.5 g.). 

For a similar purpose, this type of sensor was prepared with a hypodermic needle containing the optical Hber [29]. The accuracy obtained was 0.013 pH units. Also, Bromocresol Green (BCG) and Bromothymol Blue (BTB) immobilized covalently on a cellulose membrane, with a variation of the signal (1.6-2 V) obtained around pAJ, (7.S for BTB), helped to achieve standard deviations of less than three decimal places [30]. 

After dissolution of the triclobisonium chloride cream, the triclobisonium chloride is complexed with bromocresol green and this complex is extracted into a chloroform solution. The absorbance of this solution, as well as the absorbance of the complex similarly prepared from reference standard triclobisonium, is read at 630 nm and the amount of triclobisonium chloride present in the cream is calculated (13). 

R = bromo purple, crystal violet, methyl red, bromocresol green, phenolphthalein Scheme 5.15 Preparation of polymeric pH indicators [142, 143]... 

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