LCTech DEXTech Goes Green

Importance of the Topic

Modern laboratories seek to minimize the use of dichloromethane due to its toxicity and potential carcinogenicity. In routine analysis of dioxins (PCDD/Fs) and polychlorinated biphenyls (PCBs) in fatty samples, replacing DCM with safer solvents enhances operator safety and aligns with green chemistry principles without compromising analytical performance.

Objectives and Study Overview

This study revises the established Alox Plus clean-up method for dioxin and PCB fractionation by replacing the traditional n-hexane/DCM (50/50) solvent mix with a greener ethyl acetate/toluene (99/1) blend. The goal is to maintain speed, reliability and regulatory compliance while eliminating DCM from the workflow.

Instrumentation

• DEXTech automated clean-up system equipped with the Alox Plus cartridge
• D-EVA automated evaporation unit
• DFS high-resolution mass spectrometer (Thermo Fisher Scientific)
• GC-HRMS injection via SSL mode on a 60 m HT8 PCB capillary column (Trajan) for PCB fraction 1
• GC-HRMS injection via PTV splitless mode on a 60 m RTX Dioxin2 capillary column (Restek) for PCDD/F fraction

Methodology

The new DCM-free workflow comprises:

• Purge the solvent line of the DEXTech instrument with ethyl acetate/toluene (99/1).
• Spike 3 g of oil sample with 13C12-labelled PCDD/F and PCB standards.
• Add 1 mL toluene, adjust volume to 10 mL with n-hexane, then initiate the Alox Plus clean-up sequence.
• Collect two fractions: F1 (ndl-PCBs and mono-ortho PCBs) in 24 mL ethyl acetate/toluene, F2 (non-ortho PCBs and PCDD/Fs) in 10 mL toluene.
• Evaporate fractions to near dryness using the D-EVA system and reconstitute for analysis.
• Perform GC-HRMS analysis using appropriate columns and injection modes.

Main Results and Discussion

Comparative recovery studies showed that the DCM-free method delivers recoveries of 13C-labelled PCDD/Fs and PCBs consistently above 80 % across olive, fish and sunflower oils, matching or exceeding the classical DCM method. Proficiency testing on a PFAD material yielded z-scores within ±2 for all congeners, demonstrating accuracy equivalent to the original Alox Plus protocol.

Benefits and Practical Applications

• Rapid clean-up in 35 min for 1 g fat or 50 min for 5 g fat samples.
• Low solvent consumption and minimal fraction volumes enhance throughput and cost-efficiency.
• Simple implementation: swap the solvent bottle and purge the line.
• Compliant with European and US FDA regulations for dioxin and PCB analysis.
• Reduced laboratory exposure to hazardous DCM improves safety.

Future Trends and Opportunities

Ongoing developments in green analytical chemistry may extend DCM-free protocols to other contaminant classes and matrices. Further integration with fully automated platforms and exploration of alternative solvent systems will drive safer and more sustainable workflows. Regulatory pressure is likely to accelerate adoption of such methods across environmental and food testing laboratories.

Conclusion

The DCM-free Alox Plus method provides an effective, fast and reliable alternative for the fractionation and analysis of PCDD/Fs and PCBs in fatty samples. By maintaining high recovery rates and regulatory compliance, this approach enables laboratories to enhance safety and sustainability without sacrificing analytical quality.