Investigation of carryover or cross-contamination in the EXTREVA ASE Accelerated Solvent Extractor

Significance of the Topic

The accurate and efficient extraction of organic contaminants from solid and semisolid matrices is critical for environmental monitoring, food safety, and quality control. Carryover or cross‐contamination between samples can compromise data integrity, leading to false positives or inaccurate quantitation. Investigating and demonstrating minimal carryover in advanced extraction systems underpins confidence in high‐throughput workflows and regulatory compliance.

Study Objectives and Overview

This white paper evaluates the potential for carryover or cross‐contamination when using the Thermo Scientific EXTREVA ASE Accelerated Solvent Extractor in parallel extraction of heavily fortified soil samples. Two classes of analytes were studied: polyaromatic hydrocarbons (PAHs) spiked at 12,500 μg/kg and organochlorine pesticides (OCPs) spiked at 250 μg/kg. Following extraction of contaminated samples, blank matrix extractions were performed to quantify residual analyte levels and confirm system cleanliness.

Methodology

Sample Preparation and Extraction

• Four 10 mL stainless-steel cells were packed with a mixture of 2 g loam soil and 2 g diatomaceous earth dispersant, spiked with target standards.
• Each cell was sealed with cellulose filters and hand-tightened end caps, then loaded for parallel extraction at 100 °C and 200 psi.
• Pre‐rinsing of each fluidic pathway was performed with 10 mL dichloromethane-acetone (1:1) before the first extraction.
• Post‐extraction, extracts were collected and evaporated under nitrogen at 40 °C to 1 mL, controlled by machine‐vision level sensing.
• Blank extractions using Ottawa Sand followed under identical conditions, with a rinse between runs to simulate carryover testing.

Instrumentation Used

• Thermo Scientific EXTREVA ASE Accelerated Solvent Extractor with gas‐assisted solvent delivery and parallel extraction capability (up to 4 samples).
• Gas chromatograph–mass spectrometer (GC-MS) for PAH analysis.
• Gas chromatograph with electron capture detector (GC-ECD) for OCP analysis.

Main Results and Discussion

Carryover Assessment

• PAH recoveries from heavily spiked soil ranged from 78% to 104%, with relative standard deviations below 3.2%.
• Carryover into blank sand extracts was below 0.5% for all PAH compounds.
• OCP recoveries ranged from 81.7% to 102.2%, with RSDs under 7.9%.
• OCP carryover into subsequent blanks remained below 0.5% for all analytes.

The low carryover percentages validate the effectiveness of the extraction solvent rinse and the fully automated workflow. Minimal solvent volumes combined with rigorous rinsing ensure fluidic pathways are free of residual contaminants, even at high analyte concentrations.

Benefits and Practical Applications

• High efficiency extraction reduces solvent and time requirements compared to traditional Soxhlet methods.
• Automated parallel processing of up to four samples increases laboratory throughput and reproducibility.
• Integrated evaporation with machine‐vision volume control streamlines the workflow and minimizes user intervention.
• Proven minimal carryover supports reliable analysis in environmental monitoring, pesticide residue testing, and industrial quality control.

Future Trends and Applications

Integration of real‐time monitoring and advanced data analytics could further enhance process control. Expansion to diverse matrices (e.g., food, biological tissues) and coupling with on‐line cleanup techniques will broaden applicability. Continued development of intelligent solvent management and AI‐driven method optimization promises even greater efficiency and environmental sustainability.

Conclusion

The EXTREVA ASE Accelerated Solvent Extractor delivers fast, solvent-efficient, and reproducible extraction of PAHs and OCPs with negligible carryover. Its automated rinse protocols and machine‐vision controlled evaporation ensure sample integrity across parallel runs, making it a robust solution for demanding analytical workflows.

References

• Thermo Fisher Scientific. White paper 001431: Investigation of carryover or cross‐contamination in the EXTREVA ASE Accelerated Solvent Extractor.
• U.S. EPA Method 3545A: Pressurized Fluid Extraction.