DETERMINATION OF BENZENE RESIDUES IN RECYCLED POLYETHYLENE TEREPHTHALATE (PETE) BY DYNAMIC HEADSPACE GAS-CHROMATOGRAPHY

A dynamic headspace-gas chromatography (HS/GC) method was developed to quantitate benzene in recycled PETE material derived from 21 PETE bev erage bottles. The analytical system consisted of a purge-and-trap app aratus which was interfaced directly with a gas chromatograph/flame io nization detector. Cryofocusing and non-cryofocusing GC systems were u sed. The technique was applied to spiked PETE test samples which were prepared at various benzene concentrations ranging from 100 ppb to 117 ppm. The initial spiked benzene concentration in the PETE test sample s was determined gravimetrically. The HS/GC technique was limited by t he slow desorption rate of benzene from the PETE matrix; as a result, multipurges were performed at 60-degrees-C. Regression analysis was do ne on the multipurge data to develop a desorption model which would pr edict the total amount of benzene in the PETE. The calculated results agreed with the experimental recoveries within +/- 10%. Recovery depen ded on the initial benzene level in the PETE and ranged from 70 to 90% after the first five purges.