Isolation and quantification of dissolved lignin from natural waters using solid-phase extraction and GC/MS

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Dissolved lignin in natural waters is a key indicator of organic matter sources and transformations.
• Accurate quantification of dissolved lignin is essential for biogeochemical studies.
• Existing isolation methods can be time-consuming or alter lignin composition.

Purpose of the Study:

• To evaluate solid-phase extraction (SPE) for isolating dissolved lignin from diverse natural waters.
• To optimize SPE conditions for quantitative recovery and preservation of lignin composition.
• To compare SPE with alternative isolation techniques.

Main Methods:

• Solid-phase extraction (SPE) using C18 cartridges.
• CuO oxidation of extracted lignin.
• Gas chromatography coupled to selected-ion monitoring mass spectrometry (GC-SIM-MS) analysis of oxidation products.

Main Results:

• SPE provides low blanks and rapid cleanup, suitable for trace lignin analysis.
• SPE quantitatively recovers dissolved lignin and preserves its compositional parameters compared to direct dry-down and ultrafiltration.
• Optimal lignin recovery occurs at low pH (1.5-4.0).
• Extraction efficiency is independent of flow rate (5-15 bed volumes/min).
• Refrigeration and freezing are suitable for long-term storage of processed cartridges.

Conclusions:

• SPE is a robust and efficient method for isolating dissolved lignin from fresh, estuarine, and marine waters.
• The method is compatible with subsequent CuO oxidation and GC-SIM-MS analysis.
• SPE facilitates accurate and reproducible quantification of trace levels of dissolved lignin in environmental samples.