Evaporative Concentration of Substances Listed in the European Water Framework Directive (2000/60/EC and 2008/105/EC). A Performance Comparison Between an Automated System and a Manual System

Significance of the Topic

Modern environmental monitoring requires ever lower detection limits for trace organic contaminants in water. Evaporative concentration of extracts is a critical step to improve sensitivity in compliance with the European Water Framework Directive. Automating this step can enhance reproducibility, reduce manual labor, and increase laboratory throughput.

Objectives and Study Overview

This study compares the performance of a fully automated evaporative concentration system (GERSTEL MultiPosition Evaporation Station, mVAP) against a conventional nitrogen-blowdown device. Fifty-four priority pollutants listed in the EU directives (PAHs, PCBs, PBDEs, pesticides, halogenated hydrocarbons) were evaluated to assess recoveries, precision, and processing capacity.

Methodology and Instrumentation

Aliquots (8 mL) of acetone solutions containing 5 µg/L of each analyte were evaporated at 35 °C. System 1 (automated mVAP) employed a controlled vacuum (200 mbar), orbital agitation (250 rpm), and integrated rinsing of vial walls. System 2 (reference) used nitrogen flow (20 mL/min at 7 bar) with manual sample handling. Both systems targeted a final extract volume and transferred samples to GC-MS for analysis.

Used Instrumentation

• GERSTEL MultiPosition Evaporation Station (mVAP) with MultiPurpose Sampler and PC 3001 Vario vacuum pump
• GERSTEL MAESTRO Software for method control
• Agilent 6890 GC coupled to 5973 MSD
• PTV injector (80 °C start, 12 °C/s to 300 °C) and Optima-5-ms column

Key Results and Discussion

Both systems achieved comparable recoveries (95 %–109 %) and precision (RSD <10 %) across volatile and semi-volatile analytes. Evaporation times were similar (mVAP: 20 min; N₂ system: 22 min). The automated mVAP delivered consistent results independent of solvent type and minimized sample-to-sample variability through controlled vacuum and temperature.

Benefits and Practical Applications

• Fully automated workflow from extract concentration through solvent exchange to injection
• High throughput: up to 98 samples processed unattended versus 50 manually loaded samples
• Improved reproducibility and reduced operator time
• Compatibility with standard GC-MS and LC-MS platforms for environmental analysis

Future Trends and Opportunities

Further integration of automated evaporative concentration with on-line sample preparation and direct coupling to separation/detection systems will streamline workflows. Advances may include expanded solvent compatibility, miniaturized modules for micro-scale analysis, and enhanced software algorithms for dynamic process control.

Conclusion

The GERSTEL mVAP system matches the analytical performance of manual nitrogen-blowdown devices while providing end-to-end automation, higher throughput, and reproducible evaporation. This supports stringent trace analysis required by water quality regulations and boosts laboratory efficiency.

References

1. Ahmed M, George SC. Org Geochem. 35(2):137–155 (2004).
2. Baez ME et al. HRC-J High Res Chrom. 20(11):591–596 (1997).
3. Dettmer K et al. Chemosphere. 27(11):2111–2116 (1993).
4. Directive 2000/60/EC establishing a framework for Community water policy.
5. Directive 2008/105/EC on environmental quality standards in water policy.