Spectrophotometric Determination of Ascorbic Acid Concentration in an Unknown Solution

Ultraviolet–visible spectroscopy Absorbance Beer–Lambert law

Spectrophotometric determination of Ascorbic acid Concentration in an Unknown Solution


The naturally occurring organic compound with antioxidant properties is Ascorbic acid shortly referred as (AA). Normally the color of Ascorbic acid is white, but in some cases of impure samples it appears yellow in color. Ascorbic acid is solid in state. In water it dissolves well to give mildly acidic solutions. Ascorbic acid is one form ("vitamer") of vitamin C [1]. So, Ascorbic Acid (AA) in other terminology also called as Vitamin C. This ascorbic acid majorly helps in the maintenance of DNA, Lipids, Proteins and others in their original active, normal form.

The name of the anion Fe(CN)64− is mentioned as Ferrocyanide. This coordination complex is unreactive in aqueous solutions. Ferrocyanide is usually available as the salt potassium ferrocyanide, the formula is K4Fe(CN)6.[2]. [Fe(CN)6]4− is a diamagnetic species, compared to many salts of cyanide, these Ferro- and ferricyanides are less in toxicity, as they tend not to release free cyanide. Its reaction is its oxidation to ferricyanide:

[Fe (CN)6]4−   [Fe(CN)6]3− + e− Spectroscopically the conversion can be followed 

Now the main Aim of the procedure includes:

1. Determination of absorbance maximum ((max) of potassium ferricyanide in the range 350 nm to 550 nm, potassium ferricyanide has the chemical compound with the formula K3[Fe(CN)6] . The salt contains the octahedrally coordinated [Fe(CN)6]3− ion which is bright red in color and it is soluble in water and its solution shows some green-yellow fluorescence[3]

2. Production of calibration curve for ferricyanide at (max ,

3. Determination of stoichiometric number “n” in Eqn.(1) and

4. Determination of the concentration of Ascorbic acid (AA) in an unknown solution.

5. Study of a sample’s response to light is UV spectroscopy.

The Beer-Lambert law is the important principle involved...
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