Determination of Iron in Vitamin Supplements bySpectrophotometric Analysis
A tablet containing iron, Fe (II) fumarate (Fe2+C4H2O4 2- ) andbinder was dissolved in 0.1M HCl solution and the solution wasfiltered to remove any insoluble binder
Fe (II) in the above step was oxidized with hydrogen peroxide toFe (III) as follows 2 Fe2+ + H2O2 + H+ → 2 Fe3+ + 2 H2O
The solution prepared in above step 3 was transferred to a 1000mL volumetric flask. To this flask, 1M potassium thiocyanate (KSCN)was added and volume was brought to 1000 mL with water. Reaction ofFe (III) with KSCN formed a blue color solution.
Fe3+(aq) + SCN- (aq) Fe(SCN)2+(aq)
UV absorbance at 477 nm was measured for the solution preparedin step 3 and the absorbance value was recorded in the laboratorynotebook
Steps 1 through 4 was repeated for additional 5 tablets (sixtablets total). 6. Following are the UV absorbance values for theFeSCN complex prepared for each tablet.
Following are the UV absorbance values for the FeSCN complexprepared for each tablet.
TabletNumber              Absorbances
1 0.639
2Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.683
3Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.702
4Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.732
5Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.722
6Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.767
A calibration curve was prepared from a ferric chloride (FeCl3)standards from 20 to 60 µg/mL concentration range that provided thefollowing absorbance values.
Fe (µg/mL)     Absorbance @450nm
10Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.434
20Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.566
30Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.625
40Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.880
50Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 1.002
The mass of iron in milligram in each tablet was recorded in thelaboratory notebook. Calculate the mass of iron from the two tablesfor each tablet using the spectrophotometric method (Remember tocorrect for the dilution factor).
I made the Calibration Curve and got this equation.
y = 16.92x + 0.0064
How do I solve for the mass of iron using this equation?
