Direct quantitation of volatile organic compounds in packaging materials by headspace solid-phase microextraction–gas chromatography–mass spectrometry

The quantification of volatile organic compounds (VOCs) in flexible multilayer packaging materials using headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME–GC–MS) was studied. The analytes include 22 compounds such as aldehydes, ketones, carboxylic acids and hydrocarbons formed by thermooxidative degradation of polyethylene during the extrusion coating process in the manufacture of the packaging, and many of them are involved in the unpleasant and undesirable odour of these materials. External standard calibration using a solution of the analytes in an appropriate solvent was the first approach studied. Aqueous solutions of the analytes provided low reproducibility and the reduction of aldehydes to alcohols under the HS-SPME conditions. Hexadecane was chosen as the solvent since its polarity is similar to that of polyethylene and its volatility is lower than that of the analytes. However, hexadecane should be added to the sample before the analysis as it modifies the absorption capacity of the fibre. A 75-μm Carboxen–poly(dimethylsiloxane) fibre was used to extract the VOCs from the headspace above the packaging in a 15-ml sealed vial at 100 °C after 5 min of preincubation. The influence of the extraction time on the amount extracted was studied for a standard solution of the analytes in hexadecane, together with the influence of the volume of the standard solution and the amount of the sample placed in the vial. Standard addition and multiple HS-SPME were also studied as calibration methods and the results obtained in the quantitative analysis of a packaging material were compared.