Lab S1 Spectrophotometric Determination of Ferrous Ion
Objectives Carry out a color forming reaction for ferrous solutions. Measure the absorbance of the formed colored complex. Define the dependence of absorbance of electromagnetic radiation on concentration. Construct a calibration curve for standard ferrous solution. Determine the concentration of ferrous found in a commercial product (Fer in Sol®) oral drops. Calculate % recovery of the provided commercial product.
Principle A chromophoric reagent is used to form a stable red complex that can be measured at λmax = 508 nm
I- Construction of a Calibration Curve: From a standard stock solution of 1 x M ferrous ammonium sulfate, prepare 5 serial dilutions as follows: 1.In 100-mL volumetric flasks, pipette 1.0, 2.0, 4.0, 6.0, 8.0 mL of the standard stock solution respectively 2.To each volumetric flask, add 8 mL phenanthroline solution then add 2 mL 2M sodium acetate solution. A red complex is formed. 3.Adjust the volume to the mark using distilled water. 4.Measure the absorbance of each dilution at λ max =508 nm. 5.Insert the results in the table in your lab report. Plot a calibration curve (absorbance versus concentration) using Microsoft Excel ™.
II - Photometric determination of ferrous in Fer in sol® oral drops: In a 500-mL volumetric flask, pipette 4.0 mL of the provided drops, adjust the volume to the mark using distilled water. In a 100-mL volumetric flask, pipette 1.0 ml of the prepared dilution. Add 8 mL phenanthroline, then add 2 mL sodium acetate solution. (A red complex is formed) Adjust the volume using distilled water. Measure the absorbance at λ max = 508 nm. From the calibration curve, find the concentration of the sample by interpolation AND by substitution in the linear regression equation. Calculate the % recovery of ferrous in Fer in Sol®.
Volume (mL)Concentration (M)Absorbance Complete you lab report as indicated Calibration curve data Equation of the linear regression graph= Results : % recovery = practical conc/ labelled conc x 100