Headspace and immersive analysis of volatile compounds from environmental samples with a new sorptive extraction tool: HiSorb

Volatile organic compounds (VOCs) are important facilitators of intra- and interspecies communication between organisms. Uncovering the volatile diversity in different environments is the first step in understanding the interactions taking place in nature via volatile compounds. VOCs produced by plants and microbes can diffuse through soil and water into the gas phase above, but some remain within the solid and liquid matrix. Measuring only the gas phase can, therefore, misrepresent the chemical complexity and bioavailability in the environment. For a comprehensive assessment, it is important to characterize VOCs dispersed within the solid and liquid phases. We applied sorptive extraction (HiSorb) to different environmental samples—soil, moss, and seawater—using both headspace and direct immersive sampling and gas chromatography–mass spectrometry to analyze the VOCs captured. We determined the linear ranges, limits of detection, and precisions for standards in a complex mixture, to assess the quantitative suitability of the HiSorb method in untargeted analysis—focusing specifically on VOCs relevant for environmental samples, such as terpenes and green leaf volatiles. We also tested the effects of sampling time and temperature on the extraction efficiency and evaluated the loss of captured analytes during storage. Based on analytical method validation, the HiSorb method is not suitable for fully quantitative, untargeted analysis of complex mixtures, and optimization should be done individually for each application. We also observed the loss of some analytes during long storage, which may hinder the use in remote field work. However, we show that the HiSorb probes captured a variety of VOCs from the headspace and immersed into different environmental sample matrices and can be especially useful for qualitative or semi-quantitative VOC screening, requiring no specialized sampling setups or user expertise. Most VOCs were observed in higher amounts within the sample matrix than in the gas phase above, indicating that gas-phase analysis alone may yield biased results, and complementary immersive sampling provides a comprehensive volatile profile of the sample.