US EPA

1630291 

Journal Article 

RECENT ADVANCES IN POLYOLEFIN ADDITIVE ANALYSIS 

Nielson, RC 

1993 

Yes 

Journal of Liquid Chromatography
ISSN: 0148-3919 

16 

7 

1625-1638 

English 

10.1080/10826079308020978 

WOS:A1993KW50600016 

The extraction and quantitation of polymer additives
continues to be a very important procedure in polymer deformulation. We have previously shown
ultrasonic and microwave oven techniques to extract out antioxidants and slip agents from
polyolefins in much less time than conventional methods such as Soxhlet extraction. The ability
to reproducibly extract these materials out of polymer matrices at a high level (>90%) is
desirable to ensure that the correct amount of material is in the formulation to afford the
necessary protection during processing and end use. This paper will emphasize the ultrasonic bath
extraction and recovery of the phosphite ester, Irgafos 168, using various extraction solvents in
high density polyethylene (HDPE). The phosphite esters will hydrolyze in extraction solvents
containing alcohols (such as isopropanol, a common polyolefin extraction solvent), and also will
undergo hydrolysis during the reverse phase gradient LC run if exposed to water for too long a
period. The hydrolysis products will result in multiple peaks eluting in the chromatogram, which
make the precision of the integration (by adding the multiple peak areas) quite poor. Also, the
presence of these multiple peaks will co-elute with other antioxidants, such as Irganox 1076. The
use of solvents such as cyclohexane and methylene chloride with an ultrasonic bath provides for a
fast, reproducible method to extract these phosphite esters out without risking hydrolysis
breakdown. Conventional acetonitrile/water reverse phase gradient techniques are discussed, as
well as the use of normal phase, isocratic separations in under seven minutes. Also, flow
programming is demonstrated to illustrate the use of this technique in further optimizing the LC
analysis to improve selectivity and resolution.