Discovering the Scent of Celery: HS-SPME, GC-TOFMS, and Retention Indices for the Characterization of Volatiles

Importance of the Topic

The volatile profile of celery contributes directly to its aroma, flavor quality, and consumer acceptance. Detailed characterization of these compounds supports food quality control, flavor research, and development of value-added produce products.

Objectives and Study Overview

This study aimed to demonstrate the use of headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography time-of-flight mass spectrometry (GC-TOFMS) and retention index analysis to identify and characterize volatile compounds in celery. Emphasis was placed on resolving chromatographic coelutions and improving identification confidence through deconvolution and retention indices.

Methodology and Instrumentation

Celery Preparation and Extraction:

• Approximately 4 g of diced fresh celery placed in a 20 mL vial.
• Incubation at 50 °C for 5 min followed by HS-SPME extraction with a DVB/CAR/PDMS fiber at 50 °C for 30 min.

GC-TOFMS Conditions:

• Gas chromatograph: Agilent 7890 with LECO L-PAL3 autosampler.
• Injection: 2 min desorption at 250 °C, splitless.
• Carrier gas: Helium at 1.0 mL/min.
• Column: Rxi-5ms (30 m × 0.25 mm × 0.25 µm).
• Oven program: 40 °C (2 min), ramp 5 °C/min to 200 °C, then 10 °C/min to 300 °C (1 min).
• Transfer line and ion source at 250 °C; mass range 35–650 m/z; acquisition rate 10 spectra/s.

Key Results and Discussion

The total ion chromatogram revealed hundreds of peaks, including coeluted compounds resolved by mathematical deconvolution. An example involved 2-methyl naphthalene and tridecane, which overlapped in the TIC but were distinguished with extracted ion chromatograms and deconvoluted spectra. Retention index calculations, based on naturally occurring alkanes in the sample, supported or corrected library matches. Representative classes identified included alkanes, esters, aldehydes, ketones, terpenes, terpenoids, aromatics, alcohols, and phthalates. Notable celery aroma compounds 3-n-butylphthalide and n-butylidene phthalide were successfully detected.

Retention index data also refined tentative identifications, such as selecting α-thujene over β-thujene based on a smaller RI error, thereby improving odor property assignments.

Benefits and Practical Applications

Combining HS-SPME with GC-TOFMS and deconvolution allows comprehensive volatile profiling with higher confidence in compound identities. This approach is valuable for:

• Flavor quality control and standardization in the food industry.
• Authentication of produce and detection of adulteration.
• Research into cultivar differences and processing effects on aroma.

Future Trends and Opportunities

Advances may include integration of real-time data processing, expanded retention index libraries, machine-learning–driven deconvolution algorithms, and coupling with alternative extraction or separation techniques to further enhance sensitivity and throughput.

Conclusion

HS-SPME-GC-TOFMS with deconvolution and retention index analysis proved effective for profiling celery volatiles. The method detected hundreds of compounds, resolved coelutions, and improved identification confidence, enabling detailed aroma characterization.

References

1. NIST Mass Spectral Search Program for the NIST/EPA/NIH Mass Spectral Library Version 2.2, build Jun 10, 2014