Abstract: The oxidation of Irganox 1076 (I-1076) at a glassy carbon electrode in aqueous 60% ethanol was studied by various voltammetric techniques. Based on the results a differential pulse voltammetric method was developed for the determination of I-1076 in commercial PVC-based plastics. The plastic was extracted with acetonitrile overnight, the extract was evaporated to dryness under N2 and the residue was dissolved in ethanol. The solution was diluted with water after the addition of 1 M acetic acid/acetate buffer at pH 4.5. The differential pulse voltammogram was recorded from 0-0.8 V with a scan rate of 10 mV/s and a pulse amplitude of 50 mV using a glassy carbon disc electrode with a SCE reference electrode and a Pt wire counter electrode. The calibration graph was linear for 1-25 µM-I-1076 with a detection limit of 0.23 µM. The RSD for 10 µM-I-1076 was 3.3.%. A FIA method with pulsed amperometric detection was also developed for I-1076 in PVC. The system used a wall-jet detector cell with a glassy carbon electrode, a Ag/AgCl/3 M KCl reference electrode and a Au counter electrode. Sample solution was injected into an acetic acid/acetate buffer carrier stream (2.8 ml/min, pH 4.5) and the pulse amperometric detector was operated with a measuring potential of 0.7 V for 0.1 s and a cleaning potential of -1 V for 0.2 s. Calibration graphs were linear for 0.2-1 µM and 1-10 µM with detection limits of 0.08 µM. The RSD (n = 12) for 5 µM-I-1076 was 2.3%.

Abstract: A 5-g sample of shredded PVC food container or wrapping was extracted with a mixture of CCl4 and methanol under reflux; the extract was concentrated and then diluted with methanol to 5 mL. Chopped sample (1 g) of clothes was heated under reflux with methanolic 0.1% HCl, the extract was concentrated and diluted with methanol to 10 mL. Dioctyltin compounds (20 µL) were determined on an Asahipak GC-310H column (25 cm x 7.6 mm) at 40°C with 10 mM KH2PO4 buffer of pH 2 - methanol (2:3) as mobile phase (1 mL min-1). Dibutyltin compounds were separated from dioctyltin compounds on a Shodex DE-613p column with 10 mM phosphate buffer of pH 2.3 - methanol (1:1) as mobile phase, and then determined on a Shodex RSpak DE-613 column (15 cm x 6 mm) at 35°C with the same mobile phase (1 mL min-1). Post-column derivatization was performed with 0.1 mM morin in methanol followed by fluorescence measurement at 500 nm (excitation at 420 nm). Recoveries were 98 to 100% and detection limits were 10 ng.