Quantitative Analysis by FTIR
L. J. Mathias, M. G. Hankins, C. M. Bertolucci, T. L. Grubb, J. Muthiah, J. Chem.
Ed., (1992), 69, A217-A219
This experiment illustrates an interesting quantitative application of infrared
spectroscopy. IR spectroscopy is not often employed as a quantitative
technique, primarily because of sample preparation difficulties. Here, peak
height analysis within the same sample is used to obtain semi-quantitative
concentrations of vinyl acetate in ethylene-vinyl acetate copolymers. You will
need to learn how to obtain absorbance values for the 1020 and 720 cm -1 peaks.
Please bring any number of films to the laboratory – they will be evaluated by IR
to see if they are ethylene-vinyl acetate copolymers.
Develop techniques (in working with the TA or instructor) to stretch samples too
thick for analysis using a hot clothes iron. This will require practice – work in a
hood – be careful not to burn yourselves. This is a critical part of the sample
preparation for this experiment, keep at it until you obtain very thin films!
Samples will be taped on cardboard strips with a hole cut in them where the IR
beam passes.
Follow the laboratory procedures to obtain Beer’s law plots for the “known”
samples, and use this data to estimate vinyl acetate concentrations of unknown
samples.