TABLE OF CONTENTS Straightforward UV spectroscopy is liable to be in error because of interference by other highly absorbing impurities that may be present in the sample [59-62]. Interference by such impurities in direct UV spectroscopy has been overcome or minimised by selective solvent extraction or by chromatography [60]. However, within prescribed limits UV spectroscopy is of use and, as an example, procedures are described next for the determination of Ionol (2,6-di- tert-butyl- p-cresol) and of Santonox R (4,4 ?-thio-bis-6- tert-butyl- m-cresol) in polyolefins [63-66].
Certain additives, e.g., calcium stearate and thiodipropionate, do not interfere in the determination. Other phenolic antioxidants, e.g., Ionox 330, Topanol CA and Santonox R, do interfere.
A polymer sample (20 g) was weighed into a 250 ml round-bottomed flask and 50 ml of chloroform was added. A water-cooled condenser was connected and the flask was placed on the electric heating mantle and brought gently to boiling point. The solution was refluxed for 30 minutes at a moderate rate. After cooling, the chloroform solution was carefully decanted into a 100 ml volumetric flask (using a filter if necessary) and stoppered immediately. A further 40 ml of chloroform was added to the contents of the round-bottomed flask and a second extraction of the polymer was carried out. When cool, the contents were filtered into the volumetric flask containing the first extract. The residue was washed with sufficient chloroform to dilute it to the mark. The...
