VASE - Vacuum Assisted Sorbent Extraction Odor, Pesticide, & PAH Analysis for Dairy Products

Significance of the Topic

Analysis of volatile and semi-volatile organic compounds in dairy matrices is hindered by low analyte volatility, high fat content, and strong matrix interactions. Vacuum Assisted Sorbent Extraction (VASE) overcomes these challenges by combining solvent-free vacuum headspace extraction with a high-capacity sorbent phase, enabling sensitive and reproducible recovery of both VOCs and SVOCs while minimizing carryover and artifacts.

Objectives and Study Overview

This study evaluated VASE for comprehensive aroma profiling and trace contaminant analysis in chocolate chip cookies, cheese, and 2% milk. Key aims included demonstrating broad volatility range extraction, assessing method reproducibility, and extending quantitative headspace analysis to organochlorine pesticides and PAHs at sub-ppb levels.

Methodology and Instrumentation Used

Sample preparation involved homogenizing matrices and spiking standards when required. Tenax-packed Sorbent Pens were sealed into vials, evacuated to <0.01 atm, and equilibrated under controlled temperature, agitation, and time in a 5600 Sorbent Pen Extraction System (SPES). Pens were thermally desorbed in a 5800 Sorbent Pen Desorption Unit (SPDU) connected to an Agilent 7890B/5977 GC-MS. A four-valve flow path provided split control, water management, and forward/back-flush capabilities. Calibration used unique Pens per level in full-scan mode; surrogate internal standards supported PAH quantitation.

Main Results and Discussion

• Broad-range profiling: Over 60 flavor and odor compounds—including aldehydes, ketones, lactones, and pyrazines—were reproducibly extracted from cookies with a 15 h, 25 °C VASE run.
• Reproducibility: Duplicate analyses of cheddar and brie cheese matched closely in peak intensity and profile, demonstrating minimal carryover and high repeatability.
• Pesticide quantitation: Calibration for eight organochlorine pesticides (0.5–10 ppb) showed linear response with excellent signal-to-noise at 0.5 ppb, satisfying regulatory limits such as EPA’s 0.2 ppb threshold for heptachlor epoxide.
• PAH recovery: Fourteen PAHs (1–6 rings) were quantified in water (0.5–20 ppb) with stable recoveries; naphthalene breakthrough suggested use of longer precolumns to capture volatile aromatics.
• Milk analysis: VASE profiled compounds from formic acid to cholesterol, and PAH recoveries in milk matched water for low-molecular-weight analytes but declined for heavier PAHs, highlighting matrix effects.

Benefits and Practical Applications

• Solvent-free extraction spanning boiling points from –50 °C to over 500 °C.
• Enhanced sensitivity via near-equilibrium vacuum extraction and increased phase volume (150× SPME).
• Improved recovery of low-volatility targets and reduced matrix artifacts.
• High throughput through offline parallel extractions and compatibility with autosamplers (CTC PAL).
• Wide applicability to flavor profiling, QA/QC of food, and trace contaminant monitoring in environmental and industrial contexts.

Future Trends and Potential Applications

• Integration of isotopically labelled surrogates to enhance quantitation and compensate for MS variability.
• Use of salt addition and optimized precolumn length to reduce breakthrough and improve heavy SVOC recovery.
• Automation and coupling with SIM or tandem MS for sub-ppb detection limits.
• Expansion to other complex matrices such as soils, cosmetics, and biological fluids.
• Development of field-deployable VASE systems for on-site environmental and food safety monitoring.

Conclusion

VASE represents a robust, solvent-free headspace extraction method that extends analytical reach into the SVOC domain while maintaining high sensitivity and reproducibility. Its broad volatility coverage and simplified workflow position VASE as a powerful tool for flavor analysis, contaminant screening, and quality control in complex matrices.

References

Entech Instruments Application Note V-3741-03; Noad V.L.; Cardin D.B.; 2017.