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

Solid-phase extraction (SPE) was tested for the isolation of dissolved lign in from diverse natural waters (fresh, estuarine, and marine) in preparatio n for CuO oxidation. Capillary GC coupled to selected-ion monitoring mass s pectrometry (SIM-MS) of CuO oxidation products provides the high sensitivit y and precision required for the identification and quantification of trace levels of lignin in seawater. The low blanks and quick cleanup of Cls cart ridges support SPE for processing such samples. Comparison of SPE with othe r isolation procedures (direct dry-down and ultrafiltration) has shown that this method quantitatively recovers dissolved lignin and preserves its com positional parameters. The concentration and nature of dissolved organic ma tter appear to be primary factors that constrain the amount of water that s hould be processed to obtain quantitative and reproducible recoveries of di ssolved lignin using SPE. Highest recoveries of dissolved lignin were obtai ned at low pH (1.5-4.0) with substantial decreases at pH > 4. Extraction ef ficiencies were independent of now rate within a range of five to fifteen b ed volumes per minute (50-150 mt min(-1)), and both refrigeration and freez ing were appropriate long-term storage methods for processed cartridges pri or to elution of retained dissolved lignin.