The study of volatile organic compounds (VOCs) in soil and other complex substrates is a rapidly developing field. VOCs in soils originate from a wide variety of biological sources; bacterial, fungal, mesofaunal, and plant. They are vital to inter- and intra-species interaction and soil health, and therefore offer a potential reactive, functional diagnostic tool to determine soil quality. The standard methodology for untargeted VOC profiling in environmental samples has been headspace solid phase microextraction (HS-SPME), avoiding the need for solvent extraction procedures used in many biological soil tests. However, this technique can suffer from a lack of sensitivity due to competition between individual VOCs on the solid phases used for VOC recovery. Other common techniques used to monitor the VOC fingerprints from soils include high capacity sorptive extraction (HCSE). This study presents a novel SPME-trap-enrichment method using an automated, cryogen-free, focusing and pre-concentration trap method to reduce phase competition and increase sensitivity of analysis. This method was evaluated against single-SPME-trap and HCSE methods for sensitivity and number of compounds identified using a range of induced soil qualities (good, medium and poor). Results showed that SPME-trap-enrichment was able to identify 71% and 7% more compounds than single-SPME-trap and HCSE, respectively, using a software-based data processing approach, as well as increased total peak areas. The VOC profile was substantially affected by the extraction method used. The samples within the ‘poor’ treatment produced a larger number of aromatic, carboxylic acid and sulphur containing compound groups, while the ‘good’ and ‘medium’ groups were largely characterised by ketones and aldehydes. The potential ecological significance of the compounds identified were also explored. Of those tested, SPME-trap-enrichment represented the most robust and sensitive technique for VOC analysis, offering the potential to better elucidate the multifaceted interactions of VOCs within plant-microbial-soil systems.

土壤和其他复杂基质中挥发性有机化合物 (VOC) 的研究是一个快速发展的领域。土壤中的 VOC 来自多种生物来源；细菌、真菌、中型动物和植物。它们对物种间和物种内的相互作用和土壤健康至关重要，因此提供了一种潜在的反应性、功能性诊断工具来确定土壤质量。环境样品中非目标 VOC 分析的标准方法是顶空固相微萃取 (HS-SPME)，避免了许多生物土壤测试中使用的溶剂萃取程序的需要。然而，由于用于 VOC 回收的固相上各个 VOC 之间的竞争，该技术可能会缺乏灵敏度。用于监测土壤 VOC 指纹的其他常用技术包括高容量吸附提取 (HCSE)。本研究提出了一种新的 SPME 捕集富集方法，该方法使用自动化、无冷冻剂、聚焦和预浓缩捕集方法来减少相竞争并提高分析灵敏度。针对使用一系列诱导土壤质量（良好、中等和较差）识别的化合物的灵敏度和数量，该方法针对单一 SPME 捕集器和 HCSE 方法进行了评估。结果表明，使用基于软件的数据处理方法，SPME-trap-enrichment 能够比单一 SPME-trap 和 HCSE 多识别 71% 和 7% 的化合物，并且总峰面积增加。VOC 曲线很大程度上受所用提取方法的影响。“差”处理中的样品产生大量芳香族、羧酸和含硫化合物组，而“好”和“中等”组主要以酮和醛为特征。还探讨了所鉴定化合物的潜在生态意义。在这些测试中，SPME-trap-enrichment 代表了最强大和最灵敏的 VOC 分析技术，提供了更好地阐明植物-微生物-土壤系统中 VOC 多方面相互作用的潜力。