D-EVA – Automated EVAporation of PCDD/F Extracts to 100 - 200 μL PCB Extracts to 300 – 500 μL

Importance of the Topic

The quantification of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) at trace levels is critical for environmental monitoring, food safety and regulatory compliance. Achieving low limits of quantification (LOQs) depends on efficient clean-up and minimization of sample losses during evaporation of extracts. Conventional evaporation methods pose risks of analyte loss, cross‐contamination and require constant supervision. The development of an automated vacuum centrifugal evaporator (D-EVA) addresses these challenges and supports high‐throughput laboratories in meeting stringent performance criteria.

Objectives and Study Overview

The aim of this study was to optimize and validate the D-EVA system for reproducible concentration of PCDD/F and PCB extract fractions to minimal volumes without loss of analytes or cross‐contamination. Key goals included:

• Evaluating recovery rates of isotopically labelled standards during evaporation
• Defining suitable evaporation programs for PCDD/F and PCB fractions
• Demonstrating compatibility with automated clean-up (DEXTech) and high-resolution mass spectrometric analysis

Methodology and Instrumentation

Sample preparation involved spiking solvent blanks and a fish oil matrix with 13C-labelled PCDD/F and PCB standards. Clean-up was performed on a DEXTech Pure system using acidic silica gel, alumina and carbon columns. Evaporation steps were carried out on a Martin Christ RVC 2-33 CDplus vacuum centrifuge modified by LCTech (D-EVA) with infrared heating and pressure control down to 10 mbar.

• Evaporation programs for PCB (24 mL to 300–500 µL in 30–35 min) and PCDD/F (10 mL to 100–200 µL in 40–45 min)
• Centrifugation at 800 rpm prevents aerosol formation and cross‐contamination
• Final transfer into GC vials avoids rinsing steps, ensuring >90% recoveries

Analysis employed a DFS high‐resolution mass spectrometer (Thermo Fisher) with SSL injection on a 60 m HT8-PCB column for PCBs and PTV injection on a 60 m RTX-Dioxin2 column for PCDD/Fs.

Results and Discussion

Recovery experiments showed mean 13C recoveries of 90–105% for individual PCDD/F congeners and 85–113% for PCB congeners across solvent blanks and fish oil matrix. Evaporation to sub-200 µL volumes was achieved without sample dryness or analyte loss. The automated stop function based on LCTech sensor technology effectively prevented over-evaporation.

Benefits and Practical Applications

• High throughput: simultaneous evaporation of up to 26 PCDD/F or 23 PCB samples
• No supervision required: automated end‐point detection
• Reduced cross‐contamination: centrifugal forces retain analytes at tube bottom
• Streamlined workflow: seamless integration with DEXTech cleanup and GC–HRMS analysis

Future Trends and Potential Applications

The D-EVA concept can be extended to other volatile and semi-volatile analytes requiring trace‐level determination. Integration with robotics and online sample preparation platforms may further reduce hands-on time. Advances in sensor technology could enable even smaller end-volumes and broader solvent compatibility.

Conclusion

The LCTech-enhanced D-EVA vacuum centrifuge offers a robust, automated solution for concentrating PCDD/F and PCB extracts to minimal volumes with high recoveries, no cross-contamination and minimal operator intervention. It complements existing cleanup platforms and high-resolution mass spectrometry workflows to meet increasingly stringent analytical requirements.

Instrumentation Used

• D-EVA Vacuum Concentrator (Martin Christ RVC 2-33 CDplus modified by LCTech)
• DEXTech Pure & Heat automated clean-up system with acidic silica, alumina and carbon columns
• DFS High-Resolution Mass Spectrometer (Thermo Fisher Scientific)
• Columns: 60 m HT8-PCB (Trajan), 60 m RTX-Dioxin2 (Restek)