Page 285 - Handbook of Instrumental Techniques for Analytical Chemistry

Infrared Spectroscopy 275

Figure 15.17 Multicomponent analysis of sulfur oxygen anions over a 30-min reaction period of the anaerobic
– 2– 2– 2– 2–
aqueous decomposition of sodium dithionite. (a) [HSO 3 ], (b) [S 2 O 3 ], (c) [S 2 O 4 ], (d) [S 3 O 6 ], (e) [SO 4 ], (f)
2– 2–
[S 2 O 5 ], (g) [SO 3 ], ÆOXæ = average oxidation state, and [S] T = total sulfur. (Reprinted with permission from D.
A. Holman, A. W. Thompson, D. W. Bennett and J. D. Otvos, Analytical Chemistry, Vol. 66, No. 9, 1378–1384.
Copyright 1994 American Chemical Society.)

4. Qualitative Analysis of Multilayered Polymeric Films using
FTIR Microspectroscopy.

IR analysis can be used to determine the identities of polymer materials in a multilayered film. Using
FTIR microspectoscopy, various layers in the polymeric film can be quickly characterized. The quali-
tative analysis of a three-layer, 20-µm-thick film is described below to demonstrate such an application
(8).
The layered thin film is cut as a 2·20-mm sheet. Cross-sections of the film are obtained using a
fiber microtome. The individual section is transferred to a NaCl window on a slide positioned on the
microscope stage. FTIR spectra are recorded in the transmission mode.
This particular sample has a three-layer composition of Primacor (8 µm), nylon (10 µm), and Pri-
macor (8 µm). Primacor is a copolymer of ethylene and acrylic acid. Nylon is a polyamide polymer.
Using an FTIR microscope, infrared transmittance spectra of the multilayered film are obtained (Fig.
15.22). An IR spectrum of pure Primacor can be obtained on the exposed outside layer. The IR spec-
trum of the center layer exhibits the contributions from both nylon and Primacor. This probably results
from spatial contamination, which occurs when a specific layer of 8 to 10 µm or thinner is not masked
properly for IR spectrum acquisition due to the poor contrast between the layers or the limitations of
the aperture sizes. Functional group mapping can be performed to enhance the spatial resolution. This