Automated Solid-Phase Extraction of Phthalates for Drinking Water Samples

Significance of the Topic

Phthalates are widely used plasticizers that can leach into drinking water, posing potential health risks. Reliable detection at low parts-per-billion levels is essential for regulatory compliance and public safety.

Objectives and Study Overview

This study aimed to demonstrate an automated solid-phase extraction (SPE) workflow for trace phthalate analysis in drinking water, highlighting efficiency, reproducibility, and compliance with U.S. EPA Method 506.

Methodology and Used Instrumentation

• Automated SPE: Thermo Scientific Dionex AutoTrace 280 instrument with closed-system venting and positive-pressure operation.
• SPE media: 47 mm 3M Empore C18 disks and SolEx 6 mL C18 cartridges.
• Pretreatment: Addition of sodium thiosulfate and phthalate standard to 1 L water samples.
• Extraction sequence: Conditioning with dichloromethane, methanol, and water; loading 1.2 L sample; drying under gas; elution with acetonitrile and dichloromethane following EPA protocols.
• Analysis: GC-ECD using a Thermo Scientific TraceGOLD TG-1MS column; GC–MS for confirmatory analysis.

Main Results and Discussion

• Disk-based SPE yielded recoveries of 89–113% (RSD ≤ 17%) for six regulated phthalates, meeting EPA recovery criteria. Cartridge-based SPE showed lower reproducibility for DINP (RSD ~39%).
• Automated operation enabled processing of six samples in 2–3 hours with only 15 minutes of hands-on time, significantly increasing throughput.
• The closed SPE system reduced solvent consumption and operator exposure while ensuring constant, reproducible flow rates.

Benefits and Practical Applications

• Full compliance with U.S. EPA Method 506 without manual liquid–liquid extraction.
• Significant time and cost savings through automation and solvent reduction.
• Seamless integration into end-to-end workflows for sample preparation, evaporation, analysis, and data management.

Future Trends and Potential Applications

• Expansion of automated SPE protocols to other semi-volatile organic pollutants in environmental and industrial matrices.
• Coupling automated SPE with LC–MS/MS for multiplexed detection of emerging contaminants.
• Development of portable, field-deployable automated SPE systems for real-time water quality monitoring and high-throughput screening.

Conclusion

The Thermo Scientific Dionex AutoTrace 280 automated SPE workflow with 47 mm C18 disks offers a robust, efficient, and reproducible method for ultra-trace phthalate analysis in drinking water. It delivers regulatory-compliant recoveries, reduces solvent use, minimizes manual effort, and enhances laboratory productivity and data quality.