Decolorization Protocol

• Decolorization refers to the process of removing brightly colored organic impurities from the sample mixture. The procedure is usually carried out in the solution phase after the solid product and impurities are dissolved in a suitable solvent.
• Before beginning of decolorization, it is important to know whether the observed color is really an impurity or just the natural color of the desired product. Perform decolorization only after you have determined the color is due to an impurity.

Decolorization Depends on the Solubility of Pigment in Different Solvents

• Water extraction alcohol precipitation. Removing a small part of water-soluble pigment.
• Alcohol lifting water. Removing most fat-soluble pigment.
• Acid-base precipitation method. When the impurity pigment is some flavonoids, anthraquinone and other phenolic acid components, which can precipitate by adjusting the solution below PH3.

Decolorization Depends on the Difference of Adsorb Ability

• Physical adsorption. Polar adsorbent, such as silica gel, alumina, which can remove hydrophilic pigment. Non-polar adsorbents, such as activated carbon, pulp, talc, diatomaceous earth, which can remove lipophilic pigment.
• Chemical adsorption. For example, alkaline alumina can be used to remove some phenolic acidic pigments such as flavonoids and anthraquinones. Ion exchange resin method, phenolic acid pigments such as flavone and anthraquinone can be removed by anion exchange resin.
• Semi-chemical adsorption. Polyamide and macro-porous resin. Adsorption principle for hydrogen bonding, macro-porous resin and part of the van der Waals force. Polyamide can form hydrogen bonds with phenolic and flavonoid hydroxyl groups through the amide carbonyl group in the molecule. The free amine group on the amide bond can also form hydrogen bonds with the carbonyl group on the quinones and fatty carboxylic acids.

Decolorization by Precipitation Method

• Calcium ions in lime milk can combine with some components to form calcium chelates and calcium salt precipitates.
• Under the action of sulfuric acid, the calcium salts formed by flavonoids, anthraquinones, phenols, saponins, some alkaloids and calcium ions can be decomposed and then dissolved into water.
• However, tannin, some proteins, organic acids, polar pigments, polysaccharides and so on cannot be decomposed.

Decolorization by Flocculant Method

• Polyacrylamide, often used in beverage process, sugar process, fermentation process.
• Disodium hydrogen phosphate, trisodium phosphate, often used in beverage process, fermentation process.
• Sulfuric acid, often used in beer process, fermentation process, starch process, dairy processing technology.
• Zinc sulfate is often used in century egg process, beer process, fermentation process.
• Ferrous sulfate, often used in beverage and beer processes.

• Don't add activated charcoal to a solution that is near boiling. Violent foaming may result that can dangerously propel the solution out of the flask.
• Different decolorization methods can be used interchangeably.

Whole Slide Imaging

Transmission Electron Microscopy (TEM) Service