Migration of antioxidant additives from various polyolefinic plastics into oleaginous vehicles

The migration of the antioxidant additives pentaerythrityl tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1010) and tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168) from polyolefinic packaging into oily vehicles was investigated. The polyolefins included in the study were from the following classes: isotactic polypropylene homopolymer (PP), ethylene-co-propylene random copolymer (RACO), ethylene-propylene heterophasic copolymer and ethylene-propylene amorphous copolymer blend (EP) and high-density polyethylene (HDPE). Each polymer was additioned with Irganox 1010 (0.15%, w/w) and Irgafos 168 (0.15%, w/w) and processed into blown bottles. To study the antioxidant release process, plastic sheets were cut from the bottles and dipped for various time intervals into a mixture of five oils (caprylic/capric triglyceride, cyclomethicone, dicaprylyl ether, isohexadecane and C(12-15) alkyl benzoate) representative of lipophilic excipients used in pharmaceutical and cosmetic formulations. After exposure to the oil medium, the non-migrated Irganox 1010 and Irgafos 168 were recovered from the polymeric matrices using microwave-assisted extraction with ethyl acetate-hexane and assayed by HPLC. The leaching of the two antioxidants varied remarkably depending on the polyolefin crystallinity and structure. The amount of Irganox 1010 transferred into the contact medium at 25 degrees C decreased in the order EP>RACO>PP>HDPE. The same polyolefin ranking was observed in the case of Irgafos 168, except for PP and HDPE which exhibited similar depletion of this additive. Migration of Irgafos 168 was greater than that of Irganox 1010 and the release of both antioxidants increased at higher temperature (50 degrees C). The obtained data are useful for the selection of polyolefinic matrices as raw-materials for the production of pharmaceutical and cosmetic containers.

Microwave-assisted extraction by fast sample preparation for the systematic analysis of additives in polyolefins by high-performance liquid chromatography

This paper presents a new approach for complete and systematic analysis of organic additives in polyolefins. The proposed procedure is a convenient combination of sample preparation, performed by microwave-assisted extraction (MAE), and direct chromatographic evaluation of extract by high-performance liquid chromatography coupled with ultraviolet and evaporative light scattering detection. In particular two microwave-assisted processes are reported and discussed: the one-step MAE, useful for additives with low-medium dipolarity (like stabilizers, flame retardant, antistatics, slip and processing agents), and the two-step MAE, useful for additives with either high dipolarity (like organic salts, antigasfading, antiacid, nucleating agent) or high molecular mass (like polymeric hindered amine light stabilizers). Both the proposed processes have been tested on representative additives in five commercially common polymeric matrices, demonstrating their satisfactory analytical results, in terms of repeatability and percentage recoveries, and their good performances, in terms of safety and time/solvent consumption, in comparison with those of traditional extraction methods.

High-performance liquid chromatographic determination of some of the hydrolytic decomposition products of poly(alpha-hydroxyacid)s

An HPLC procedure is described for the separation and identification of some hydrosoluble by-products resulting from the hydrolytic degradation of poly(alpha-hydroxyacid)s having biomedical interest: poly(L-lactide), poly(DL-lactide), poly-(glycolide) and poly(lactide-co-glycolide). Peak identification was performed by comparing the respective retention times with those of pure standards. It was observed that optimum shape and separation of peaks are considerably affected by the composition of the mobile phase, consisting of acetonitrile (A) and a 0.006 M K2HPO4 buffer (B), and, in particular, its pH and A:B ratio, which had to be adjusted to around 5.8 and 75:25 (v/v), respectively. Under the investigated experimental conditions (aqueous suspension, 100 degrees C for 12 h under stirring), poly(L-lactide) is quite stable, poly(glycolide) degrades easily to glycolic acid, whereas poly(DL-lactide) and poly(DL-lactide-co-glycolide) exhibit intermediate behaviour. Upon hydrolytic decomposition, these poly(alpha-hydroxyacid)s yield not only the corresponding acids, but also their linear dimers and, possibly, trimers, tetramers and higher oligomers.