Experiment #3: Spectrophotometric Determination of Tartrazine
The objectives of this lab include- illustrating the use of the spectrophotometer in chemical analysis, and generating a standard, or calibration curve, then using that curve to determine the value of an unknown substance. The spectrophotometer is one of the most powerful tools used in chemistry to find the concentration of substances in solution. It compares the colors of a known and an unknown solution, that comparison then leads to a quantitative estimate of the concentration of trace amounts of colored materials in that solution.
Chemicals and Materials
40 mL standard Tartrazine solution
100 mL beaker
Spectrometer with Labquest
Acquire 40mL of the standard tartrazine solution in a 100mL beaker. Make sure the beaker is clean and dry.
Dilute the original standard solution into the following concentrations in separate beakers using de-ionized water.
Prepare 3 different solutions:
7.5mL standard + 2.5mL deionized water (75% solution)
5.0mL standard + 5.0mL deionized water (50% solution)
2.5mL standard + 7.5mL deionized water (25% solution)
After all of the solutions are prepared, obtain a cuvette from your professor (special sample cell).
Prepare a blank, by filling up your cuvette ¾ with deionized water.
Wipe down the outside of each cuvette with the lint-free tissue.
Handle only at the top edge, and while using gloves.
Dislodge all bubbles.
Always position cuvette so that light passes through the clear sides
Connect the spectrometer to LabQuest and choose New from the File menu.
Put the blank cuvette into the Spectrometer.
Choose the calibration option on the Sensors Menu.
Determine the Optimal Wavelength for creating this standard curve and set up on the data-collection mode.