Measuring Concentrations of Volatile Organic Compounds in Vinyl Flooring
The initial solid-phase concentration of volatile organic compounds (VOCs) is a key parameter influencing the emission characteristics of many indoor materials. Solid-phase measurements are typically made using solvent extraction or thermal headspace analysis. The high temperatures and chemical solvents associated with these methods can modify the physical structure of polymeric materials and consequently affect mass transfer characteristics. To measure solid-phase concentrations under conditions resembling those in which the material would be installed in an indoor environment, a new technique for measuring VOC concentrations in vinyl flooring (VF) and similar materials was developed. A 0.09 m2 section of new VF was punched randomly to produce approximately 200 0.78-cm2 disks. The disks were milled to a powder at -140o C to simultaneously homogenize the material and reduce the diffusion path length without loss of VOCs. VOCs were extracted from the VF particles at room temperature by fluidized bed desorption (FBD) and by direct thermal desorption (DTD) at elevated temperatures. The VOCs in the extraction gas from FBD and DTD were collected on sorbent tubes and analyzed by gas chromatography/mass spectrometry. Seven VOCs emitted by VF were quantified. Concentration measurements by FBD ranged from 5.1 μg g-1 VF for n-hexadecane to 130 μg g-1 VF for phenol. Concentrations measured by DTD were higher than concentrations measured by FBD. Differences between FBD and DTD results may be explained using free-volume/dual-mobility sorption theory, but further research is necessary to more completely characterize the complex nature of a diffusant in a polymer matrix.