An analytical comparison of the potential of HS/SPME-GC-MS and HS-GC-IMS for the analysis of bacterial volatile organic compounds.

Microbial volatile organic compounds (mVOCs) are a group of low molecular mass metabolites produced by microbial cells that play indispensable roles in molecular communication among species and among kingdoms. Currently, the analysis of mVOCs is gaining relevance due to its applicability in several fields. In this paper, the possibilities of using gas chromatography (GC) coupled to ion mobility spectrometry (IMS) or to mass spectrometry (MS) detectors to identify and quantify mVOCs in microbial samples were studied. Two different extraction methods before GC separation were tested when MS was used as detector: headspace (HS) and solid-phase microextraction (SPME). For this purpose, Pseudomonas simiae strain PICF7 isolated from olive roots was chosen as a test sample. Solid cultures of PICF7 inoculated in vials were analyzed by HS-GC-MS, SPME-GC-MS and HS-GC-IMS. HS-GC-IMS allowed for the detection of 37 signals from mVOCs emitted by PICF7, whereas 18 peaks were detected by SPME-GC-MS and 7 peaks by HS-GC-MS. Of these, 4, 7 and 11 signals were tentatively identified by using HS-GC-MS, SPME-GC-MS and HS-GC-IMS, respectively. SPME-GC-MS and HS-GC-IMS proved to be complementary due to their different selectivity. Additionally, an analysis of analytical parameters using standards concluded that due to its low quantification limits, HS-GC-IMS is particularly well-suited for quantifying mVOCs from PICF7 emitted at very low levels of concentration. This work provides worthy data that can be taken into account for future studies involving analysis of mVOCs, including biocontrol research, monitoring microbial contamination in foodstuff and bio-processes, or clinical diagnosis of microbial infections.