Optimization and Comparison of Methods for Sampling Volatile Organic Compounds in Breath by Solid Phase Microextraction and Gas Chromatography-Mass Spectrometry

Eray Schulz 1,2, Mark Woollam 2, Paul Grocki 2, and Mangilal Agarwal 1,2,3

1. UPUI Department of Chemistry and Chemical Biology,

2. Integrated Nanosystems Development Institute,

3. IUPUI Department of Mechanical and Energy Engineering

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Abstract: 

Volatile organic compounds (VOCs) can be detected in exhaled breath as potential biomarkers for medical conditions. The gold standard for analysis is gas chromatography-mass spectrometry (GC-MS) and can be coupled with various sampling methods. One method is Tedlar bag sampling, which allows for reduced sampling volumes, facile collection of many samples in the field, and requires no additional devices that require disinfection between uses. Our work aims to compare different methods for preconcentrating VOCs using solid phase microextraction (SPME). A previously optimized SPME fiber coating was used for extracting VOCs from breath collected using two methods. One method directly extracted VOCs from the Tedlar bag (Tedlar-SPME) and the other cryothermally transferred VOCs from a Tedlar bag to a vial (Cryotransfer). Various extraction periods (5-, 10-, and 15- minute) were tested for Tedlar-SPME to develop a time-efficient method with high sensitivity. The Cryotransfer method was previously optimized and allows for both long-term storage at -80℃ as well as SPME GC-MS analysis. Cryotransfer displayed the greatest sensitivity, having the highest signal for most VOCs detected in exhaled breath samples. However, smaller VOCs including acetone and isoprene were detected with the highest sensitivity using Tedlar-SPME. Overall, both methods are capable of detecting a wide variety of VOCs in breath including previously identified biomarkers for different diseases. The Cryotransfer method may be optimal when collecting a large number of samples using Tedlar bags, as it allows for long-term storage of VOCs at -80℃, while Tedlar-SPME may be more efficient when targeting relatively smaller VOCs.