Quantitative analysis of atmospheric volatile organic pollutants by thermal desorption gas chromatography mass spectrometry

Abstract

An analytical method has been developed and validated for analyzing 48 volatile organic compounds (VOCs) that were found to be present in substantial quantities in the atmosphere in Singapore. Air samples were collected by active sampling using Tenax/Carbopack X multisorbent tubes and were evaluated by Thermal Desorption Gas Chromatography Mass Spectrometry (TD-GCMS). Experiments conducted using standards demonstrated excellent repeatability with relative standard deviation (%RSD) values lesser than 10%, good linearity with R² values of at least 0.99 for a wide range of concentrations between 0.02 and 500 ng, breakthrough values 5% or lower, tube desorption efficiencies close to 100% and good recoveries between 61% and 120%. Sampling volumes and flow rates were tested and selected by evaluating the performance of the multisorbent tubes. 30 mL min⁻¹ was selected as the optimal flow rate for different sampling volumes depending on the individual compound's breakthrough value and reproducibility during air sampling. Most of the target analytes exhibited acceptable breakthrough of 5% or less, reproducibility within 20% deviation and method detection limits below 500 ppbv. Criteria established by the United States Environmental Protection Agency (USEPA) for sorbent tube sampling (EPA TO-17) were met for most compounds of interest.