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

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.