A Method to Characterize Natural Organic Matter using Size Exclusion Chromatography with Charged Aerosol Detector
The main objective of this research was to develop a new detection method to characterize natural organic matter (NOM) using size exclusion chromatography (SEC) with charged aerosol detector (CAD). Conventional UV detectors have difficulty in detecting hydrophilic NOM. Attaching the CAD to the SEC system to form an SEC-UV-CAD detection series is a possible solution to detect hydrophilic NOM in water samples. The CAD showed similar performance as the UV detector, and the CAD showed beneficial capabilities for detecting low UV-absorbing compounds such as phenylalanine. The amino acids’ chlorination experiments and the raw water resin fractionation experiments were performed to evaluate the preliminary SEC-UV-CAD method. Both experiments indicated the CAD chromatograms have severe baseline noise and inorganic interfering issues. Several short experiments were attempted to improve these issues: CAD showed potential to detect desired hydrophilic NOM with concentrated raw water; replacement of SEC analytical column to C18 analytical column significantly reduced the baseline noise when detecting selected amino acids; precipitated anions with silver acetate and barium acetate removed sulfate and chloride peak signals from CAD chromatograms; strong anion exchange resin (i.e. DSC-SAX) can remove unwanted anions and separate NOMs by their affinity to the resin. The results from the C18 analytical column and SAX resin experiments have shown a great potential to characterize hydrophilic NOM samples. Further studies using C18 analytical column and SAX analytical column on detecting hydrophilic NOM were recommended.