Qualitative Analysis of Coconut Water Products using Stir Bar Sorptive Extraction Combined with Thermal Desorption-GC/MS

Importance of the Topic

Stir bar sorptive extraction (SBSE) coupled to thermal desorption GC/MS provides a solvent-free, sensitive approach to characterize trace flavor and safety-related compounds in coconut water products.
As demand increases for natural isotonic beverages, reliable analysis of antioxidants, residual pesticides, packaging migrants, and off-flavor constituents is essential for quality and regulatory compliance.

Goals and Study Overview

• Develop a rapid, efficient SBSE-TD-GC/MS method for commercial coconut water products.
• Screen for volatile flavor compounds, plasticizers, antioxidants, and pesticide residues.
• Compare compositional differences among natural and flavored samples.

Used Instrumentation

• Gerstel MultiPurpose Sampler (MPS) with thermal desorption unit (TDU).
• Gerstel Cooled Injection System (CIS 4) PTV inlet.
• Agilent 7890 GC with 5975C Inert XL MSD (triple axis detector).
• Gerstel Twister stir bars (SBSE media).

Methodology

The study employed 10 mL coconut water samples spiked as needed and stirred with Twister bars for 90 min. Twisters were thermally desorbed in splitless mode (TDU to 280 °C, CIS ramp to 275 °C) onto a 30 m Rxi®-5Sil MS capillary column (0.25 mm × 0.25 µm). Helium constant flow (1.2 mL/min) and full scan MS (50–450 amu) recorded target analytes. Salting out with 30% NaCl enhanced extraction of more polar volatiles.

Key Results and Discussion

Natural samples exhibited diverse ketones, acids, esters, and lactones with brand-dependent variations in octanoic, decanoic, and dodecanoic acids and flavor esters. Flavored variants showed characteristic peaks for added ingredients (e.g., methyl anthranilate for grape flavor, limonene for citrus blends) and common stabilizers like triethyl citrate. Salting out improved recoveries of lower log Kow compounds. SBSE achieved sub-ppb sensitivity for 20 organophosphorous pesticides (RSD 2.5–17%). Multi-desorption mode aggregated extracts from multiple bars, amplifying signal by up to 4.7×.

Benefits and Practical Applications

• Solvent-free extraction reduces chemical waste and sample preparation time.
• High sensitivity and precision for flavor profiling and contaminant screening.
• Versatile platform applicable to other drink matrices requiring trace analysis.

Future Trends and Opportunities

Integration of SBSE-TD-GC/MS with automated multi-sampling and advanced data analytics can further streamline high-throughput beverage quality control. Emerging sorbent materials may expand extraction selectivity to a wider polarity range. Coupling with tandem MS or high-resolution MS will enhance compound identification and quantitation.

Conclusion

The presented SBSE-TD-GC/MS workflow offers a robust, efficient solution for comprehensive analysis of coconut water products, enabling detailed flavor characterization and safety assessments with minimal solvent use and high reproducibility.

References

Pfannkoch E.A., Stuff J.R., Whitecavage J.A. Qualitative Analysis of Coconut Water Products using SBSE with Thermal Desorption-GC/MS. Gerstel AppNote 5/2012.