A solvent-free thermal desorption-gas chromatography-tandem mass spectrometry method (TD-GC-MS/MS) for the determination of polycyclic aromatic hydrocarbons in gas phase airborne samples

A solvent-free, thermal extraction method for analysis of polycyclic aromatic hydrocarbons (PAHs) in gas phase airborne samples was developed. A fully automated thermal desorber (TD) coupled with highly selective and sensitive gas chromatography-tandem mass spectrometry (GC-MS/MS) was used to determine the concentration of trace level PAHs. Air sampling was conducted to tune the sampling and analytical conditions. Various instrument operating parameters such as sorbent tube desorption temperature/time, cold trap desorption temperature/time, outlet split ratio, tube storage stability, as well as air sampling flow rate and time were tested to optimize the analytical conditions. Method performance showed linearity in broad range (0.01 to 10 ng) with regression coefficients of external calibration curves (R-2) >0.998 for all targeted PAHs. Method detection limit (MDL) was between 0.01-0.05 ng per tube. The method precision (<20 %) and accuracy were also satisfactory, obtaining quantitative recoveries (mean values between 80 and 120 %). The method has been applied for both outdoor and indoor air analysis. Small volume of air sample (<144 L) was sufficient for the PAH analysis. Naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, anthracene, fluoranthene, acenaphthene, fluorene, pyrene, and acenaphthylene are the primary PAHs in the gas phase for both indoor and outdoor air. Naphthalene and its two methylated compounds: 1-methylnaphthalene and 2-methylnaphthalene accounted for 47.7 % and 81.7 % of the total gas phase PAHs for outdoor and indoor, respectively. Using thermal extraction instead of organic solvent extraction for sample pretreatment makes the method sustainable and in consonance with the principles of green chemistry. No solvent and time-consuming extract step are needed. The method greatly improved the analytical process with a fully automated TD-GC-MS/MS instrument.