Optimizing Extraction of Multianalyte Suites from Water Samples Using Layered Solid Phase Extraction Columns

Importance of the Topic

Layered solid phase extraction (SPE) addresses a common challenge in environmental and industrial water analysis: simultaneous extraction of analytes with widely varying polarities from a single sample. This approach streamlines workflows, reduces sample volume requirements, lowers solvent consumption and overall cost, while maintaining high recovery rates for pesticides, phenols, PAHs, phthalates and more.

Study Objectives and Overview

The primary aim was to evaluate a novel SPE column combining two sorbent layers—one weakly retentive and one strongly retentive—for efficient, concurrent extraction of non-polar and polar organic pollutants from drinking water. The layered approach was compared against conventional single-phase columns to demonstrate improvements in retention, elution and analyte recovery.

Instrumentation

• SPE Column: ISOLUTE C8/ENV+ layered cartridge (weak C8 upper layer, strong ENV+ lower layer)
• Elution Solvent: Acetone/ethyl acetate (1:1, v/v)
• Sample Acidification: HCl to pH 2, methanol (1%, v/v) pre-load
• Flow Control: Up to 60 mL/min during sample loading
• Post-Extraction: Evaporation to dryness, reconstitution for chromatographic analysis

Methodology

• Column conditioning with methanol, equilibration with water
• Loading of acidified drinking water sample (up to 500 mL)
• Drying column for 10 minutes under vacuum or nitrogen
• Sequential elution of non-polar analytes from the upper layer, followed by polar analytes from the lower layer
• Separate chromatographic conditions optimized for each analyte class

Key Results and Discussion

• Recovery rates exceeded 80% for over 40 target compounds, including chlorinated pesticides, base-neutral and acid herbicides, phenols, PAHs and phthalate esters.
• Layered columns prevented breakthrough of polar analytes on a weak sorbent and avoided strong retention of non-polar analytes on a single strong phase.
• Elution volumes were reduced compared to single-phase columns, thanks to targeted retention zones for each analyte polarity.
• Comparative tests showed improved throughput and lower solvent usage, without compromising method sensitivity or selectivity.

Benefits and Practical Applications

• Consolidation of multiple extraction steps into a single SPE cartridge.
• Significant cost savings in consumables and solvents.
• Suitability for routine monitoring of drinking water, wastewater, industrial effluents and environmental samples.
• Flexibility to customize layer combinations (e.g., C2/C18, C8/ENV+, C18/ENV+) based on analyte profiles.

Future Trends and Opportunities

• Integration with on-line SPE coupled to LC-MS/MS for fully automated workflows.
• Development of multilayer cartridges incorporating ion-exchange or mixed-mode sorbents for broader target classes.
• Application in non-aqueous matrices such as food, biological fluids and complex industrial streams.
• Miniaturization towards micro-SPE and disposable formats for field-deployable analysis.

Conclusion

Layered SPE columns offer a versatile, efficient solution for extracting diverse analyte suites from water in a single run. By strategically combining weak and strong sorbent phases, they overcome retention and elution conflicts inherent to single-phase methods, delivering high recoveries, reduced solvent use and enhanced laboratory productivity.

Reference

1. Davi et al., International Journal of Environmental Analytical Chemistry 74(1–4):155–166 (2000).