Solid phase microextraction for urinary VOC analysis using portable GC-MS: Method development and validation against...

Biological volatile organic compounds (VOCs) are expressed in noninvasive sample types such as urine and have emerged as promising biomarkers for disease detection. Gas chromatography-mass spectrometry (GC-MS) is the gold standard for VOC analysis, providing robust separation, quantification, and identification capabilities. While highly precise and accurate, benchtop GC-MS instruments require a large physical footprint and trained personnel for operation and data interpretation. Advancements in portable GC-MS technology have enabled point-of-care VOC analysis outside traditional laboratory settings, though most systems are designed for environmental and hazardous material detection. Therefore, the current study sought to develop a new method which is optimized to detect biological VOCs in urine headspace through solid phase microextraction (SPME) coupled with portable GC-MS. Method development included optimization of sample preparation, on-column, and MS parameters to improve sensitivity, repeatability, and chromatographic resolution. The SPME-based method was compared to another sampling method using the standard air probe, which demonstrated VOCs were enriched in SPME with an average log₂ fold change equal to 3.5. Intra- and inter-day repeatability was benchmarked through analysis of UTAK urine standards, which showed that VOCs generally displayed relative standard deviation (RSD) values below 25 %. Finally, samples from three healthy volunteers and the UTAK standard (n = 3 samples each) were analyzed using the portable GC-MS. This showed that the portable system could discern unique VOC trends between the volunteers. Compound identities and quantitative signal patterns were independently confirmed using a benchtop GC-MS, thus bringing confidence in the accuracy of the portable platform.