The bromocresol green is an organic colorant belonging to the triphenylmethane family. Its scientific name is 3,3 ', 5,5'-tetrabromo m-cresolsulfonphthalein. Its chemical formula is Ctwenty-oneH14Br4OR5S. This substance complies with the characteristics and properties of a pH indicator. For this reason it is used for this purpose.
It has the ability to react to pH change in the range 3.8 to 5.4, where it changes from yellow to blue-green. The bromocresol green pH indicator is synthesized from the addition of various bromine molecules to purple cresol; process known as bromination.
It is used as a pH indicator for volumetric analysis in chemistry laboratories. It is also useful for coloring the running front in the separation of proteins and DNA in the agarose gel electrophoresis technique. Likewise, bromocresol green is used in the thin-layer chromatography technique..
Finally, it is important to note that this substance should not come into direct contact with skin and mucous membranes, as it is an irritant substance. It can also generate toxic fumes in the event of fires..
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Bromocresol green occurs as a greenish-brown crystalline solid. It has a molecular mass of 698.04 g / mol, a melting point between 217-218 ° C and its density is 0.979 kg / L. Bromocresol green decomposes at 225 ° C.
It is slightly soluble in water, moderately soluble in benzene, and soluble in ethanol, diethyl ether, ethyl acetate, and NaOH..
On the other hand, the bromocresol green pH indicator has an isosbestic point at 515 nm. This means that at that wavelength the substance maintains its absorbance, regardless of the pH in which it is found..
Weigh 0.10 g of bromocresol green and dissolve in 7.2 ml of 0.020 M NaOH. Make up to 250 ml with distilled water..
It should be stored at room temperature, in a well-ventilated place.
Weigh 40 mg of bromocresol green and dissolve in 17 ml of absolute ethanol and 0.58 ml of 0.1 mol / L NaOH. Make up the volume with distilled water up to 100 ml.
It is used in chemistry laboratories, as a pH indicator for volumetric analysis.
Bromocresol green has been used to color the running front in the separation of proteins and DNA in the agarose gel electrophoresis technique..
This technique is used for the separation of complex mixtures.
Bromocresol green is used as a developer, especially for substances that contain carboxylic acids and sulfonic acids or also to separate substances that have a pKa below 5.
Chen et al. Described a technique for detecting DNA using bromocresol green and a common spectrofluorometer to measure the intensity of scattering of resonance light. They got good results.
A biosensor is an electronic device to which a telltale substance has been attached. This, when reacting with a certain biological substance, converts the biochemical signal into an electrical signal that can be measurable.
There are optical biosensors to which bromocresol green has been attached for the determination of serum albumin. The biosensor has a detector cell that captures the absorption of light at a wavelength of 630 nm.
The reaction detects the color change from yellow to green when bromocresol green binds to serum albumin at a pH of 3.8.
Different international organizations consider bromocresol green as a product with a health risk 2. This means that it presents a moderate risk. Regarding flammability and reactivity, it is classified with a 1 and a 0 respectively; i.e. there is a slight risk of flammability and there is no risk of reactivity.
Depending on the type of exposure with the compound, certain health problems can occur. Among them are the following: inhalation of vapors, direct contact with skin and mucous membranes, among others.
In this sense, the inhalation of vapors produces inflammation in the respiratory tract. If there is contact with the skin, irritation occurs in the affected area.
If eye contact occurs, irritations of the ocular mucosa may occur, and if absorbed it may cause nausea, vomiting, headaches, vertigo and drunkenness..
In case of fires it is important to know that bromocresol green can generate some toxic vapors, such as hydrogen bromide and sulfoxides..
Wash the affected area with plenty of water for 15 minutes in case of skin contact. If the substance has splashed on the ocular mucosa, it should be washed with plenty of water with the eyes open..
As an adjuvant treatment, an emollient cream can be used on the affected skin to relieve irritation. If irritation persists, see a dermatologist.
In case of inhalation, move the patient to a well ventilated place; and if there are signs of suffocation, give assisted breathing.
Bromocresol green cannot be close to the following substances, as they are incompatible:
- Organic nitrogen compounds.
- Alkaline earth metals.
- Perchloric, chromosulfuric and nitric acids.
- Perchlorates.
- Halogenates.
- Chromium trioxide.
- Halogenoxides.
- Nitrogen and non-metallic oxides.
In case the substance is accidentally spilled, it must be collected mechanically with absorbent materials. Dispose of in an appropriate container. Should not be poured down the drain.
Although the effect of this substance on the environment and on human health is not known, it is recommended not to dump its waste directly onto the ground, or into water sources without first having been treated..
In this sense, Guarín and Mera studied the effect of heterogeneous photocatalysis, using a titanium dioxide catalyst, together with a discontinuous reactor (Batch type), and under artificial UV radiation..
They obtained a high degradation and mineralization of the bromocresol green (84% and 82.5%) respectively. Therefore, these types of procedures are recommended for the treatment of liquid waste containing bromocresol green..
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