TABLE OF CONTENTS Headspace GLC analysis is a method used to monitor a vapour over a polymeric matrix. It is a very effective technique, but may require more time and effort than direct injection. This method can be performed manually, when a vial containing the monomer is heated, an equilibrium is established, for volatile compounds between the sample and the headspace above it. Because no dissolution step is required, sample viscosity problems and loss of response due to dilution are eliminated. Automated headspace analysis units are available from instrument manufacturers, as well as multiple extraction systems. Any analytically useful headspace method must obey Henry s law:
where P B is the partial pressure of solute B (in solvent A), ? is the proportionality constant and X B is the mole fraction of solute B.
There are two basic principal methods of headspace analysis in polymers. In one method a solution of the polymer is examined, in the other method solid polymer is examined directly. When working with polymer solutions, headspace equilibrium is more readily obtained than the solid approach and the calibration procedure is simplified.
In the solid polymer approach the residual monomer is partitioned between the headspace and the polymer phase. The monomer concentration in the head space is determined and the original concentration in the polymer is calculated. Since polymer standards of known monomer content are not readily available, the headspace monomer concentration must be related to the original concentration in the polymer either by assuming 100%...
