Innovative Sampling and Pre-concentration of PAHs and Microplastics in Environmental Water for TD-GC-MS Analysis

Pollution in environmental waters poses a risk to natural ecosystems, to people using those ecosystems, and to the broader community via potential contamination of drinking water supplies. Therefore, many jurisdictions must ensure regulatory compliance via regular testing. Such tests must be sensitive and quantitative, and must also be scalable to large sample batches, with simple sample prep a key advantage.

Here, we demonstrate the quantitative detection of two very different pollution types – polycyclic aromatic hydrocarbons (PAHs) and microplastics – using gas chromatography—mass spectrometry (GC-MS) for both. For PAHs, we employed high-capacity sorptive extraction (HiSorb ) probes to extract analytes via direct contact between the water matrix and a sorptive phase, with subsequent thermal desorption of the probe to release analytes. Microplastics filtered from water were pyrolyzed offline, and the pyrolyzate was analysed by thermal desorption. This methodology enables larger sample sizes than typical pyrolysis-GC-MS, improving reproducibility, and reduces damage to instrument components. For both PAHs and microplastics, desorbed analytes were concentrated on a focusing trap prior to GC-MS injection, ensuring their transfer to the GC column in a narrow band of vapour for optimum chromatography.

With the methods described, we achieved detection limits of less than 6 ng/L (parts per trillion) for all PAH compounds tested – well within stringent EU requirements for drinking water. The microplastics method was applied to particles extracted from various components of a sewage treatment plant, allowing us to characterise the fates of polymers as they move through the treatment stages. Although these two methods took quite different approaches – sorptive extraction versus pyrolysis and direct desorption – both utilise the same core trapping technology, enabling sharp, readily identifiable peaks, and can be run on a single system if required.