The purposes of this experiment are (1) to introduce the basic concepts important to the study of atomic absorption spectroscopy, specifically the operation of a Varian AA Spectrometer and the meaning of absorption as related to metals analysis, and (2) to measure the concentration of an absorbing species in a sample by applying Beer's Law.

Your lab book introduction should therefore, include:

the theory behind atomic absorption spectroscopy, especially as it relates to flame AAS.

information about the operation of an atomic absorption spectrometer, with diagrams of its internal schematics, and a short description of how each of the following parts works:

• light source
• atomizer
• monochromator
• detector

explain what is meant by ppm

There are several good websites where you can find the information you need. The best starting point is Dr. Tissue's website at Virginia Tech:   www.chem.vt.edu/chemed/ac-meths.html.

Procedure: Safety Goggles are a must at all times when using the AAS!!

Part A.  Preparation of Copper Standards

Make up standard solutions of 20.0, 10.0, 5.0, 2.0, 1.0 and 0 ppm from a 1000 ppm stock solution of Cu. First make up 100 mL of a 100 ppm stock solution, then use it to make up 25 mL of each of the standards. Use 1% nitric acid to dilute all of the solutions. The 0 ppm solution will serve as the blank.

Part B. The Varian AAS

The instructor will demonstrate the operation of the Varian AAS, pointing out each part and its purpose. You should make detailed notes in your lab book as each is explained. Be sure to note all of the safety precautions.

Part C. Determination of the amount of copper in a mineral supplement.

Dissolve a tablet in 25.00 mL 6M HCl, heat for 20 minutes, and then filter using standard gravity filtration. Measure the absorption of the blank first, then each standard starting with the 1 ppm one, then with the vitamin tablet solution.

Results:

Draw your Beer's Law graph using your standards as you did in Experiments 3 and 4, and use your equation of the line to calculate the concentration of copper in your vitamin tablet solution.