Toward an Optimized Dynamic Headspace Method for the Study of Volatiles in Low-Density Polyethylene

Abstract

A dynamic headspace technique for detecting C6−C14 volatile organic compounds (VOCs) in low-density polyethylene (LDPE) is discussed in which VOCs are purged with N2, trapped at ambient temperatures on Tenax-GC, and identified by gas chromatography/mass spectrometry. The experimental variables are quantitatively modeled to enhance sensitivity of the technique. The rate of extraction of VOCs from LDPE and the rate of isothermal desorption of VOCs from Tenax-GC are first-order processes with rate constants of 2.79 × 10-5 and 1.53 × 10-3 s-1 respectively. Approximately 4.2% of extractable VOCs are present in the vapor phase at ambient temperature, and 21% of VOCs are liberated instantaneously from Tenax-GC during thermal desorption at 200 °C. The chromatographic peak area associated with each VOC, and the total peak area in the chromatographic window, vary with desorption temperature in accordance with the van't Hoff isochore with an “average” desorption enthalpy of 45.5 kJ mol-1. Keywords: Low-density polyethylene (LDPE); dynamic headspace sampling; gas chromatography/mass spectrometry (GC/MS); volatile organic compounds (VOCs); Tenax-GC; purge and trap; mathematical modeling

Estimations of isoprenoid emission capacity from enclosure studies: measurements, data processing, quality and standardized measurement protocols

“…All these materials can adsorb significant quantities of organic compounds (Harogoppad and Aminabhavi, 1991). Although the adsorption and desorption characteristics of polymers used most frequently in emission studies have not been studied quantitatively for key volatiles emitted from plants, studies on organic vapors of environmental concern have suggested that polymers such as neoprene and low-density polyethylene, used by default in commercial systems, have potentially significant adsorption/desorption problems for VOC studies (Allaire et al, 2003;Avison et al, 2001;Hartman, 1999;Hodgson et al, 1998;Manura, 1999). Apart from adsorption on polymers, in commercial gas-exchange systems, traces of silicone oil are present in O-ring seals, and in CO 2 cartridges, and in the match valve of Li-Cor 6400 system, introducing additional memory effects and contamination problems due to solubilization and evaporation of anthropogenic and biogenic VOCs in oil (Geron et al, 2006a).…”

“…As the result of slow time-and temperature-dependent decomposition, rubber and plastic materials may also constitute a contamination source of VOCs inherent to the material (Ezquerro et al, 2003;Fujii et al, 2003;Hartman, 1999;Hodgson et al, 1998;StewartJones and Poppy, 2006;Westerhout et al, 1997). Apart from tubing and chamber wall materials, adhesive tapes are often used to attach films or tubing to support structures or to attach heating wires to tubing.…”

Review of Volatile Organic Compounds Derived From Polyethylene

“…These include sensory evaluation (2,8,11,33,45,(47)(48)(49)(50)58,(86)(87)(88)(89)(90)(91)(92)(93)(94)(95)(96)(97), GC (30,34,86), and GC-MS (8,30,33,35,45,48,82,(87)(88)(89)(90)(91)(92)(93)98,99). A variety of techniques are used in conjunction with chromatographic analysis for the sampling and detection of VOCs that originate from PE.…”

“…A variety of techniques are used in conjunction with chromatographic analysis for the sampling and detection of VOCs that originate from PE. These include dynamic headspace GC-MS (2,8,88,99), GC-olfactory detection (8,30,35,79,94,95,98), selective volatile extraction (34,35,98,100), supercritical fluid extraction (101-104), vacuum distillation (98,105) and water/steam extraction (82). In addition, a portable odor meter (OM) (8,32) and various "electronic nose" devices (106-108) have also been used to assess the level of odor in PE formulations.…”

Evaluation of multiple solid-phase microextraction as a technique to remove the matrix effect in packaging analysis for determination of volatile organic compounds

“…However, the volatile organic compounds produced in the extrusion-coating process can migrate from the packaging to its content and modify its organoleptic properties [1]. These compounds have been mainly identified as carbonyl compounds in a number of reports [2][3][4][5][6][7][8].…”