Extraction of Acrylamide from Coffee Using ISOLUTE® SLE+ Prior to LC-MS/MS Analysis

Importance of the Topic

Acrylamide formation during coffee roasting is a concern due to its potential health risks. Reliable quantitation of trace levels of acrylamide in different coffee matrices (ground, instant, decaffeinated) is essential for quality control and regulatory compliance. The method combines supported liquid extraction (SLE) and LC-MS/MS to achieve sensitivity down to 1 ng/mL.

Objectives and Study Overview

This study aims to develop a rapid, robust, and selective protocol for extracting and quantifying acrylamide in coffee samples using ISOLUTE® SLE+ columns followed by LC-MS/MS detection. Key goals include:

• Achieve high recoveries across various coffee types.
• Establish linear calibration from 1 to 128 ng/mL.
• Minimize matrix interferences from coffee pigments and oils.

Methodology

• Sample Pre-treatment:
  
  1. Ground coffee: 60 g percolated with 1500 mL boiling water (40 mg/mL solids).
  2. Instant coffee: 2 g dissolved in 250 mL boiling water (8 mg/mL solids).
  3. Calibration: Prepare 128 ng/mL over-spiked solution, serially dilute to 1 ng/mL in control coffee, add internal standard (13C3-acrylamide) and ammonia.
• Supported Liquid Extraction (ISOLUTE® SLE+ 1 mL):
  
  1. Load 0.5 mL basified sample onto SLE+ column.
  2. Wait 5 min for absorption, then elute with ethyl acetate:tetrahydrofuran (1:1 v/v, 2 × 2.5 mL) into tube containing ethylene glycol.
  3. Dry under nitrogen or air stream, reconstitute in water (200 µL).

Instrumentation

• Extraction: ISOLUTE® SLE+ 1 mL columns (Biotage).
• Manifolds: VacMaster-10/VacMaster-20 or PRESSURE+ PPM-48.
• Evaporation: SPE Dry (SD-9600-DHS) or TurboVap LV.
• HPLC: Waters Acquity with Phenomenex Hydro C18 column (50 × 2 mm, 4 µm) at 40 °C, mobile phase A: 0.1% formic acid in water, B: 0.1% formic acid in methanol, gradient for polar retention, flow 0.3 mL/min, injection 10 µL.
• MS/MS: Waters Quattro Premier, ES+, MRM transitions 71.9→55.2 V, 74.9→58.2 V, desolvation 450 °C, source 120 °C.

Main Results and Discussion

• Calibration: Linear response from 1 to 128 ng/mL, r² = 0.998 in coffee matrix.
• Retention time: 1.02 min for both analyte and internal standard.
• Recoveries: Fresh roast 81% (RSD 8.2%), instant 82% (RSD 5.5%), decaffeinated 73% (RSD 3.7%) at 64 ng/mL spike.
• Matrix cleanup: SLE efficiently removes coffee pigments and oils, producing visibly clean extracts despite initial basification‐darkened sample.
• Additional notes: Ammonia basification enhances recovery; ethylene glycol prevents complete dryness during evaporation; high aqueous mobile phase requires specialized stationary phase and equilibration.

Benefits and Practical Applications

• Fast and robust sample preparation suitable for routine QA/QC laboratories.
• High selectivity and low detection limits suitable for regulatory monitoring.
• Adaptable to different coffee formats without extensive method modification.

Future Trends and Applications

• Integration with high-throughput automation for large sample batches.
• Extension to other food matrices susceptible to acrylamide formation.
• Development of miniaturized SLE formats and green solvents to reduce waste.

Conclusion

The presented SLE-LC-MS/MS protocol using ISOLUTE® SLE+ columns delivers a sensitive, selective, and efficient approach for acrylamide determination in various coffee types, achieving recoveries above 70% and detection limits at 1 ng/mL. Its simplicity and performance make it a valuable tool for routine analysis and regulatory compliance.

References

• Biotage Application Note AN796, 2013.