Overview
For the standards, use Beer's Law and Excel to convert %T to absorbance. The standards should be presented in properly labeled figures (see the syllabus) with absorbance on the Y axis and wavenumbers on the X axis. Spectra for shoe samples must say what shoe is being shown in the figure caption, and will have %T on the Y axis. Infrared spectra must be included for the standards and unknowns with the major bands identified. Annotations can be done with pen, rather than digitally, as long as they're legible.
Discussion
For this laboratory, the following must be included in the discussion:
Which band(s) in the IR spectrum did you use to determine the ethylene content of the co-polymer? Which band(s) did you use to determine the vinyl acetate content? To which functional groups and vibrational modes do these bands correspond?
2. For the standards, how do the absorbance intensities change as the composition changes?
Are these changes consistent with compositional changes? Explain
- 3. Is it possible to distinguish between the three insoles with only ATR-IR?
4. Is this technique suitable for routine forensic analysis of copolymer samples? Justify your answer.
References
Laboratory adapted from: K.R. Williams, "Analysis of ethylene-vinyl acetate copolymers: a combined TGA/FTIR experiment," J. Chem. Ed. 1994, 71, A195.
Report Checklist
-Header
-Abstract - What are you trying to find? How are you finding it? What are your main results?
-Methods - You can say "We followed the lab handout." and leave it at that if that's all you did. If you made any changes or did things differently, that needs to be described. Do not just rewrite the handout; that's a waste of time and I'm not reading that.
-Three standard spectra: AT1231, AT1821A, and SA340502 Y axis converted to absorbance, wavenumbers on X axis
-Caption or legend
-Annotations of absorption features
-Proper range with flipped x axis
-Three shoe spectra
-% Transmittance on Y axis, wavenumbers on X axis Caption or legend
-Annotations of absorption features
-Proper range with flipped x axis - see Figure 5, below
-Discussion: Must be in complete sentences and not just answering the question (i.e. don't say
"I's 55+5 mg", say "We determined that there was 55+5 mg of iron in the fresh tablet sample")
Polythylene wavenumbers, functional groups, vibrational modes Polyvinyl acetate wavenumbers, functional groups, vibrational modes Standards: absorbance changes with composition Distinguishing insoles Suitability