High Pressure Size Exclusion Chromatography (HPSEC) Determination of Dissolved Organic Matter Molecular Weight Revisited: Accounting for Changes in Stationary Phases, Analytical Standards, and Isolation Methods

Abstract

We reassessed the molecular weight of dissolved organic matter (DOM) determined by high pressure size exclusion chromatography (HPSEC) using measurements made with different columns and various generations of polystyrenesulfonate (PSS) molecular weight standards. Molecular weight measurements made with a newer generation HPSEC column and PSS standards from more recent lots are roughly 200 to 400 Da lower than initial measurements made in the early 1990s. These updated numbers match DOM molecular weights measured by colligative methods and fall within a range of values calculated from hydroxyl radical kinetics. These changes suggest improved accuracy of HPSEC molecular weight measurements that we attribute to improved accuracy of PSS standards and changes in the column packing. We also isolated DOM from wetlands in the Prairie Pothole Region (PPR) using XAD-8, a cation exchange resin, and PPL, a styrene-divinylbenzene media, and observed little difference in molecular weight and specific UV absorbance at 280 nm (SUVA) between the two solid phase extraction resins, suggesting they capture similar DOM moieties. PPR DOM also showed lower SUVA at similar weights compared to DOM isolates from a global range of environments, which we attribute to oxidized sulfur in PPR DOM that would increase molecular weight without affecting SUVA.

Environmental and Agricultural Relevance of Humic Fractions Extracted by Alkali from Soils and Natural Waters

“…The degree to which this binding occurs is dependent on both the POP and humic DOM properties, such as octanol/water partition coefficients ( K OW ) and other determinants of polarity. Because humic DOM is significantly more polar than octanol, humic DOM partition coefficients ( K DOM ) are typically 1 to 10% of the analytes’ K OW values (Chiou et al, 1986; Chin et al, 1997; Neale et al, 2011, 2012; Wei‐Haas et al, 2014). Persistent organic pollutants that have a K OW of 10 4 L kg −1 or greater will readily partition into humic DOM with K DOM values of >10 2 to 10 3 L kg −1 , depending on the humic DOM properties.…”

Soil Organic Matter Characterization by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR MS): A Critical Review of Sample Preparation, Analysis, and Data Interpretation

“…There are a wide variety of SPE cartridges that retain targeted or broad molecular features and must be selected based on the design of the experiment . The recovery of SOM from this method is highly variable and depends greatly on the cartridge being used, the origin of the SOM, and the elution procedure, ,, with recoveries varying between 20% and 90%. , Addressing the source of variable yields is challenging as there is often no reliable way to identify whether the retention or elution were incomplete. ,, …”

Fenton pre-oxidation of natural organic matter in drinking water treatment through the application of iron nails

“…For molecular weight (MW) analysis, a calibration was performed using a set of four sodium polystyrene sulfonates (PSS, Polymer Standards Service GmbH, Germany) together with Acetone (R² = 0.998). Of the various standards available for MW measurement, PSS have been widely applied [53][54][55][56][57][58][59][60] as they are more similar to NOM with regards to charge density [53,54]. After the calibration step, a semi-logarithmic linear calibration curve was obtained and used to determine the MW.…”