Optimization of an analytical method for the determination of PAHs in tobacco and tobacco smoke by GC-MS
Polycyclic aromatic hydrocarbons (PAHs) are an extensive group of compounds formed as a result of incomplete combustion of carbonaceous materials and are known components in mainstream cigarette smoke. Many PAHs have been identified by IARC as probably or possibly carcinogenic to humans and their quantitation is of much interest to regulating bodies. Currently, 16 PAHs are included on the FDA list of harmful and potentially harmful constituents (HPHC).
The purpose of this study was to develop and validate a single method for 15 of the HPHC listed PAHs using gas chromatography mass spectrometry (GC-MS). Several aspects of the instrumental method were critical to ensuring a robust method was developed.
Many of the PAHs are structural isomers and discrimination by GC-MS can prove extremely difficult; retention time becomes critical to the correct identification of each PAH. The choice in column and temperature gradient is driven by the separation of critical pairs of PAHs, which would otherwise co-elute. The temperature of the GC inlet can have a dramatic impact on the outcome of analytical results and must be optimized for the best possible responses for all 15 HPHCs simultaneously. Surprisingly, the optimum inlet temperature for this method was determined to be 250 °C, significantly lower than other investigators and instrument specialists have recommended. Improvement in peak response and peak shape were observed using a combination of reduced inlet temperature and shorter run time (<30 minutes). The most surprising effect was upon the dibenzopyrenes, where the responses were observed to increase at lower inlet temperatures and the calibration curves, initially quadratic, became linear.