Procedures: 500 mg of the sample was weighed into a 50 ml plastic
bottle. 50 ml of distilled water was added and shaken for 1 h in a
mechanical shaker. This was filtered into a 50 ml volumetric flask
and made up to the mark. Then 5 ml of the filtered was pipetted out
into a test tube and mixed with 2 ml of 0.1 M FeCl3 in 0.I N HCl and
0.008 M potassium ferrocyanide. The absorbance was measured
at 120 nm within 10 min.
My questions are:
-what is the function of 0.1 M of FeCl3 in 0.1 N HCl?
-what is the function of the 0.008 M potassium ferrocyanide?
-finally, what limitation(s) if any does this method have?
Quantification of tannins can be carried out by the method of Van-Buren and Robinson (1981) method. 50 mg of solvent fraction is suspended in 100 ml of distilled water, shaken for 1 hr in a mechanical shaker and filtered. combine 5 ml of it with 2 ml of ferric chloride in 0.1 normal hydrochloric acid and 0.008 molar potassium ferro-cyanide. OD is measured at 120 nm within 10 min and tannins contents are expressed as percentage of the dried fraction. 0.1 M of FeCl3 in 0.1 N HCl will terminate the reaction. It will show redox reaction, involving oxidizing sulphur compounds and Fe III in presence of chloride ions. Potassium ferricyanide is used to detect ferrous iron in biological tissue. Potassium ferrocyanide is the inorganic compound with formula K4[Fe(CN)6] · 3H2O. It is the potassium salt of the coordination complex [Fe(CN)6]4−. This salt forms lemon-yellow monoclinic crystals.Treatment of potassium ferrocyanide with nitric acid gives H2[Fe(NO)(CN)5]. After neutralization of this intermediate with sodium carbonate, red crystals of sodium nitroprusside can be selectively crystallized.
Upon treatment with chlorine gas, potassium ferrocyanide converts to potassium ferricyanide:
2 K4[Fe(CN)6] + Cl2 → 2 K3[Fe(CN)6] + 2 KCl
This reaction can be used to remove potassium ferrocyanide from a solution.
A famous reaction involves treatment with ferric salts to give Prussian blue. With the approximate composition KFe2(CN)6, this insoluble but deeply coloured material is the blue of blueprinting
This method can not detect other metal based compounds, enzymes and electrolytes and evaluate oxidizing capacity.
Sir what will be the procedure if our extract is in dried form via rotatory evaporator
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