title: Microwave-assisted oxidation of phosphite-type antioxidant additives in polyethylene film extracts.
abstract: Two oxidation methods for reducing the analysis time required to determine Irgafos 126 and Irgafos 168 by pressurised liquid extraction (PLE) and high-performance liquid chromatography (HPLC) were optimised and compared. Analyte oxidation was performed using sodium peroxodisulphate (SPD) as oxidation agent and two different heating methods: with a hotplate and a reflux apparatus; and with a microwave oven. The influence of variables, such as oxidation time, temperature and sodium peroxodisulphate concentration was studied using a central composite design in order to optimise experimental conditions. A temperature of 68 degrees C for 2.5h and a SPD concentration of around 6 x 10(-4)M were required for conventional oxidation, while a temperature of 120 degrees C for 30 min and a SPD concentration of 4 x 10(-4)M were found to be the best for microwave-assisted oxidation. After optimising the methods, their repeatability values were calculated and the two methods were applied to a solution containing other additives in order to check that they were not affected by the oxidation treatment and thus confirm that the methods could be used for oxidation of I126 and I168 in pressurised liquid extracts of polyethylene film samples before their determination by HPLC. Finally, the methods were applied to the analysis of antioxidants in polyethylene film samples.
authors.affiliation: Department of Chemistry, University of La Rioja, C/Madre de Dios 51, E-26006 Logroño (La Rioja), Spain.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Garrido-López
authors.forename: Idoia
authors.initials: I
authors.lastname: Sancet
authors.forename: Patricia
authors.initials: P
authors.lastname: Montaño
authors.forename: Rosario
authors.initials: R
authors.lastname: González
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Tena
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004355:Drug Stability; D008872:Microwaves; D010084:Oxidation-Reduction; D017905:Phosphites / Q000737:chemistry*; D011095:Polyethylenes / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry
chemical_list: D000975:Antioxidants; D017905:Phosphites; D011095:Polyethylenes; D017670:Sodium Compounds; D013431:Sulfates; C083748:tris-(2,4-di-tert-butylphenyl) phosphite; C024625:sodium persulfate