|Case 1: The Case of the Fraudulent Vanilla
A. Real vanilla is the product of the vanilla orchid, but it is very expensive – consequently, there is often a temptation to sell a) imitation vanilla or b) adulterated forms of pure (or artificial) vanilla
i. Vanillin, the chief flavor component of vanilla can be produced cheaply
from wood pulp. It is OK to be used as artificial vanilla but must be labeled as such.
ii. Coumarin is sometimes added to vanilla to increase the vanilla flavor. However, because it is hepatotoxic, it has been banned as a food additive in the US since 1940.
B. The Case: How do we determine if vanilla extract being sold as the real thing is artificial vanilla or even worse?
III. Topics that can be included (may or may not be)
[A. Homogeneous/heterogeneous mixtures, etc....students read only]
B. (Protons, Nectrons, Electrons) = isotopes
C. Mass spectroscopy (high and low res), GC/MS
D. Precision and accuracy
[ E. Moles, molecules, molecular formulas, combustion analysis] – could cover/overlap with next case?
IV. Presentation/introduction of topics as related to case
A. Part 1
1. What is forensics, what is chemistry, relationship between the two
2. Activity 1: Make vanilla flavored liquid nitrogen ice-cream [ homogenous mixture, etc.]
3. Where does vanilla flavoring come from?
4. Introduce case
5. Activity 2: How do we know its vanilla?
a. Physical properties – mp, density of pure vanillin?
b. Density lab – how get density if its a powder?
c. Introduce sig figs, accuracy, precision?
d. But what if it’s in a mixture?
6. How do we know it’s “real” vanilla?
a.What sorts of questions do we need to ask? What tools do we need to use to answer them? [homogeneous mixtures, etc..]
B. Part 2 – maybe we can identify a pure compound (such as vanillin) easily, but to really answer the question we need to deal with more complex mixtures – what tools (intellecutal and physical) do we need to see if we’re being ripped off or poisoned?
1. We need to use mass spectroscopy – what’s that and how does it work?
2. In order to do that we need to understand more about the atom and its components
3. Let’s look at a brief history of the atom.
4. Activity 3 – Vacuum tubes, Crook’s tube, etc?
5. A GC/MS contains a gas chromatograph (which allows for separation) connected with a mass spectrometer which allows for identification.
6. MS works upon many of the same principles as did the vacuum tubes of early experimenters.
7. How does this help us to a) find vanilla in a mixture? b) find out if the vanilla is real?
C. Part 3 – Isotopes
1. Activity/Demo 4 :Magic ice cubes? (D2O vs H2O)
2. A mass spectrometer is isotope specific as well as mass specific
3. The atomic mass of an element on the p.t. is an average of the specific isotopes.
4. The isotope ratio of an element can be modified by processing through a living system such as a plant (c.f. study on D2O with plants)
5. The 13C/12C isotope ratio is different in vanillin produced in the vanilla orchid than that produced from wood (luckily) b/c the vanilla orchid fixes carbon using the CAM pathway (as opposed to the C4)
D. Part 4 -– So what’s in the vanilla
1. Activity 5 – Run GC/MS on a) pure vanillin b) artificial vanilla c)real vanilla d) coumarin?
2. On our instrument we can probably see if vanilla would contain coumarin because there are different peaks, but how can we tell the vanilla’s apart using C-12/C-13 ratio’s – need higher res? [I’ll have to look into this]
3. Activity 6– try it on high res at online virtual mass spec lab.
Case 2 or 3: Arson Accelerant Detection? Can learn info applied from MS in case 1, apply to learning Lewis Structures, VSEPR theory, molar mass or maybe combustion analysis.