Isolation and characterization of estuarine dissolved organic matter: Comparison of ultrafiltration and C sub(1) sub(8) solid-phase extraction techniques

• Published in: Marine chemistry Vol. 96; no. 3-4; pp. 219 - 235
• Main Authors: Simjouw, J P, Minor, E C, Mopper, K
• Format: Journal Article
• Language: English
• Published: 01.09.2005
• Subjects: Brackish
• ISSN: 0304-4203
• DOI: 10.1016/j.marchem.2005.01.003

Characterization of dissolved organic matter (DOM) from aquatic environments has always been constrained by the ability to obtain a representative fraction of the DOM pool for analysis. Ultrafiltration or extraction, commonly using XAD or C sub(1) sub(8) sorbents, is therefore generally used to concentrate and desalt DOM samples for further analyses. In this study, we compared ultrafiltration and C sub(1) sub(8) solid-phase extraction disks (SPE) as DOM isolation methods for estuarine samples. We also evaluated the use of the C sub(1) sub(8) SPE disks to isolate low-molecular-weight DOM (LMW-DOM) in the filtrate from ultrafiltration. The isolates from both methods and the LMW-DOM C sub(1) sub(8)-extracts were characterized using Fourier transform infrared spectroscopy (FTIR) and direct temperature-resolved mass spectrometry (DT-MS). Based on mass balance and blank measurements, we found that the C sub(1) sub(8) SPE disks can be used to isolate bulk DOM and LMW-DOM from estuarine samples. FTIR and DT-MS analysis show that C sub(1) sub(8)-extracted DOM and ultrafiltered high-molecular-weight DOM (HMW-DOM) differ markedly in chemical composition. The HMW-DOM is enriched in (degraded) polysaccharides along with aminosugars when compared with the C sub(1) sub(8)-extracted DOM. The C sub(1) sub(8)-extracted DOM appears enriched in aromatic compounds, probably from lignin and/or aromatic amino acids in proteins. C sub(1) sub(8) SPE of LMW-DOM samples from ultrafiltration increases the recovery of DOM from the total sample up to about 70%, compared to around 50% using ultrafiltration alone. Thus, a majority of the DOM can be isolated from estuarine samples by a combination of these techniques.