Page 258 - Handbook of Instrumental Techniques for Analytical Chemistry

248 Handbook of Instrumental Techniques for Analytical Chemistry

• Identification of reaction components and kinetic studies of reactions
• Identification of molecular orientation in polymer films
• Detection of molecular impurities or additives present in amounts of 1% and in some cases as
low as 0.01%
• Identification of polymers, plastics, and resins
• Analysis of formulations such as insecticides and copolymers

Samples

State

Almost any solid, liquid or gas sample can be analyzed. Many sampling accessories are available.

Amount

Solids 50 to 200 mg is desirable, but 10 µg ground with transparent matrix (such as KBr) is the mini-
mum for qualitative determinations; 1 to 10 µg minimum is required if solid is soluble in suitable sol-
vent.

Liquids 0.5 µL is needed if neat, less if pure.

Gases 50 ppb is needed.

Preparation
Little or no preparation is required; may have to grind solid into KBr matrix or dissolve sample in a
suitable solvent (CCl 4 and CS 2 are preferred). Many types of sample holders and cells are available.
Water should be removed from sample if possible.

Analysis Time
Estimated time to obtain spectrum from a routine sample varies from 1 to 10 min depending on the type
of instrument and the resolution required. Most samples can be prepared for infrared (IR) analysis in
approximately 1 to 5 min.

Limitations

General
• Minimal elemental information is given for most samples.
• Background solvent or solid matrix must be relatively transparent in the spectral region of in-
terest.
• Molecule must be active in the IR region. (When exposed to IR radiation, a minimum of one vi-
brational motion must alter the net dipole moment of the molecule in order for absorption to be
observed.)