2. What is Spectroscopy?  There are about 12 types of spectroscopy.  It involves ALL parts of the electromagnetic spectrum  We are specifically studying: Atomic Absorption Spectroscopy Sending a beam of visible light through a sample and measuring how much of the light is absorbed by that sample.

3. Why?  By looking at the absorbance of light, we can determine the concentrations and types of a substance found in a solution.  Meaning… How much of THIS is in THAT.  And… What is THIS made of?

4. Who uses it?  Medical Field  Radiology Technicians  Astronomy  Analytical and Physical Chemists  Environmental Scientists and Chemists  Quality Control Chemists  Medical Examiners  Forensic Scientists and Chemists  Toxicology

5. Why is it called Spectroscopy? Spectroscopy = Spectrum = Electromagnetic Spectrum = LIGHT!

6. Atomic Absorption Spectroscopy Uses the spectrum of VISIBLE LIGHT.  Wavelengths we will be measuring: 700 nm to 400 nm = 7 x 10 -7 m to 4 x 10 -7 m We will be taking our readings in nanometers (nm)

7. Demo…  Let’s take a look at the instrument: Spectrophotometer

8. How can we determine the concentration of a substance in a solution? Table 2: The Absorbance Reading for Each Sample SampleAbsorbanceConcentration (mol/L) 10.0151.70E-07 20.0898.50E-07 30.1661.70E-06 40.8298.50E-06 51.5931.70E-05 Unknown0.047To be Determined Make solutions of known concentrations using the substance you are measuring. Place them in spectrophotometer and read absorbance.

9. Make a Graph with a Linear Line

10. Now place your unknown in the spectrophotometer. It will read the absorbance. Place the absorbance on your calibration curve to find concentration. Unknown Absorbance = 0.047

11. Use your equation:  Use the equation of the line to find EXACT concentration.  Y=mx+b  y = 93836x + 0.0088  Y= Absorbance  X=Concentration

12. Looking Ahead:  Lab intro due on Monday to proofread  Collecting Samples (Next Tuesday)  Using Excel to make graphs and figures (Next Thursday)  How to calculate the concentrations of your known standard solutions (Next Thursday)  Using pipets and glassware to perform dilutions (Monday Sept 15)