Palladium (Pd) nanoparticle catalysts were electrodeposited onto a graphite electrode by cyclic voltammetry (CV) technique from a 0.5 M HCl solution containing 0.2 M PdCl 2 , and then a film of polypyrrole (PPy) was immobilized onto the asprepared Pd-coated graphite electrode, leading to a PPy/Pd-coated electrode. Pd particles were repeatedly electrodeposited on the PPy/Pd-coated electrode to generate a Pd/PPy/Pd sandwich structured composite coated electrode. This developed composite electrode showed a satisfactory electrocatalysis toward the formic acid oxidation (FAO). The catalysis mechanism of the sandwich structured Pd/PPy/Pd composite catalyst toward FAO was also discussed on the basis of the obtained cyclic voltammograms and FT-IR spectra.

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A gas chromatography-mass spectrometry (GC-MS) method was developed for the determination of 46 plasticizers in food contact polyvinyl chloride (PVC) packaging materials and their migration into food simulants, i. e. water, 3% acetic acid, 10% ethanol and olive oil. Plasticizers in the PVC packaging materials, aqueous food simulants and olive oil food simulants were extracted by the dissolution-precipitation, liquid-liquid extraction and gel permeation chromatography (GPC) approaches, respectively. The extracts were analyzed by GC-MS in selective ion monitoring (SIM) mode and quantified using the external standard method. The cal-ibration curves were linear in the ranges of 0.1-2.0 mg/L with the correlation coefficients of 0.9910-0. 999 9. The limits of detection were from 0. 005 mg/kg to 0. 05 mg/kg ( S/N = 5 ). The recoveries at 3 spiked levels were 69.51%-107. 21% and the relative standard deviations (RSDs n = 6) ranged from 3.53% to 18.95%. These results show that this method is fast, sensitive and accurate for the qualitative and quantitative determination of plasticizers in food contact plastic products and 4 types of food simulants.

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