Question

Report: Report the individual concentration in [M] of Tartrazine and Sunset Yellow in the sample.

Certificate of Analysis Purities:

Tartrazine (M.W. 534.36): 89.0% (Calculated from Carbon, Nitrogen Analysis)

Sunset Yellow (M.W. 452.37): 96.2% (By HPLC)

Weight of Standards:

Tartrazine: 0.1006 Gm

Sunset Yellow: 0.1000 Gm

Absorbances: 427 nm 4   81 nm

Tartrazine: 0.936    0.274

Sunset Yellow: 0.414    0.956

Sample: 0.539    0.409

Data Analysis

•Determine the weight of Tartrazine or Sunset Yellow in the standards by multiplying the weight of standard recorded by the fraction of compound indicated from the Certificate of Analysis (the percent divided by 100).

•Determine the moles of Tartrazine or Sunset Yellow in the standards by dividing the weights determined in step (1) by the molecular weights of the compounds (Tartrazine has a molecular weight of 534.36 g/mol, Sunset yellow has a molecular weight of 452.37 g/mol)

•Determine the molarity of the compounds by dividing the moles of compound weighed by the volume in liters the compounds were diluted to (0.100 L in this case).

•Multiply the molarity above by any dilutions that were applied, which this case is 2/100.

These are the concentration of the standard solutions in M (mol/L).

Calibration: Calculate the molar absorptivity ε at each wavelength for each analyte by dividing the absorbance value at each wavelength for a given analyte by the concentration of that analyte. This will result in four molar absorptivity coefficients.

??1(427)=??(427)/??1 stand

??2(427)=??(427)/??2 stand

??1(481)=??(481)/??1 stand

??2(481)=??(481)/??2 stand

Reference Solution Evaluation: Using the calibrated ε values from above, and using the reference solution absorbance values at the two λmax wavelengths, solve the two equations for the molar concentrations of the Tartrazine (C1) and Sunset Yellow (C2) below.

(1) ?Total(ref) (427)= ??1(427)??1 ref + ??2(427)??2 ref

(2) ?Total(ref) (481)= ??1(481)??1 ref + ??2(481)??2 ref

If the reference concentrations are within 5% of their actual values then the linearity of the calibration and the non-interference and independence of the spectra has been sufficiently verified.

Unknown Solution Determination: As described in the Introduction section, solve the following simultaneous equations for the concentrations of FD&C 5 and FD&C 6 in your unknown sample:

?Total(sample)(427)= ??1(427)??1 sample + ??2(427)??2 sample

?Total(sample)(481)= ??1(481)??1 sample+ ??2(481)??2 sample

Substitution of the absorbances for the samples mixture (?Total (427) and ?Total (481)) into the above equations along with the four ε values from the calibration step, provided two simultaneous equations with two unknowns, ??1 sample and ??2 sample for FD&C 5 and FD&C 6. Apply simple algebra to determine the mathematically resolved values of ??1 sample and ??2 sample for the compounds FD&C 5 and FD&C 6.