MEPS and It’s Using in Sample Preparation in Brewing Analytics

Importance of the Topic

Sample preparation is critical for accurate determination of flavor-active compounds in beer. Gas chromatography requires effective extraction, concentration and cleanup to handle the complex beer matrix. Miniaturized and automated approaches accelerate analysis, reduce solvent consumption and minimize error‐prone manual steps.

Objectives and Overview of the Study

This study introduces Microextraction by Packed Sorbent (MEPS) as a novel, scaled-down solid-phase extraction technique tailored for brewing analytics. It overviews MEPS principles, evaluates its performance for free fatty acid analysis in beer and assesses compatibility with existing GC workflows.

Methodology and Instrumentation

• MEPS Format: Gas-tight 100–250 µl syringe packed with 1–2 mg sorbent (silica-based C2, C8, C18, polymeric phases, MIP or monolithic).
• Conditioning: 30–50 µl methanol followed by 30–50 µl water or 0.1 % formic acid.
• Sample Loading: 25–250 µl sample drawn at ~20 µl/s, repeated up/down cycles to concentrate analytes on sorbent.
• Washing: 50–250 µl water (0.1 % formic acid) at 50 µl/s to remove matrix interferences.
• Elution: 50 µl organic solvent (e.g. methanol/water 95:5) or 10 µl chloroform; optional heating to 40 °C to enhance desorption.
• Reconditioning: Sequential rinses with elution and washing solvents (up to five cycles) reduce carryover to <0.1 %.

Used Instrumentation

• MEPS syringe units (SGE Analytical Science).
• Gas chromatograph with splitless injector and flame ionization detector (FID) at 250 °C.
• DB-Wax capillary column (10 m × 0.18 mm i.d., 0.18 µm film).
• Carrier gas: Helium 5.0 at 210 kPa head pressure.

Key Findings and Discussion

MEPS effectively extracted free fatty acids from beer using only 100 µl of sample and 10 µl of eluent. GC-FID chromatograms showed clear separation of C4–C16 fatty acids with minimal background and negligible carryover. The protocol proved rapid, reproducible and directly compatible with standard GC injection.

Benefits and Practical Applications

• Drastic reduction in sample and solvent volumes compared with conventional SPE.
• High sample throughput through automated MEPS workflows lowers hands-on time.
• Direct injection of small elution volumes streamlines GC and LC analyses.
• Low carryover and improved precision support trace-level quantification.

Future Trends and Potential Applications

• Expansion to other beer flavor compounds (esters, aldehydes, phenols).
• Integration with automated analytical syringes (eVol) for fully online MEPS.
• Adaptation to LC–MS platforms for polar or thermally labile analytes.
• Broader use in environmental monitoring, food safety and industrial QC.

Conclusion

MEPS represents a powerful alternative to conventional SPE, SPME and SBSE in brewing analytics. Its small-volume, automated format offers rapid, cost-effective sample preparation with low solvent waste, making it ideal for routine quality control and research applications in beer analysis.

References

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2. Horák T. et al.: Modern sample preparation in beverage GC analysis, Kvasny Prum. 56, 2010.
3. Čulík J. et al.: SPE and GC-MS of aromatic alcohols in beer, Kvasny Prum. 55, 2009.
4. Hage T.: SPE of free fatty acids in beer, Proc. Fourth Eur. Conf. Food Chemistry, 1987.
5. Abdel-Rehim M.: MEPS in packed syringe, J. Chromatogr. B 801, 2004.
6. Blomberg L.G.: MEPS and monolithic tips, Anal. Bioanal. Chem. 393, 2009.