The determination of diol impurities in methoxy poly(ethylene glycol)s (mPEG)s is of high importance, e.g., in the area of pharmaceutical applications, since mPEGs are considered the gold standard—based on properties of biocompatibility, stealth effect against the immune system, and well-established procedures used in PEGylation reactions. Herein, we communicate a straightforward and fast approach for the resolution of the PEGdiol impurities in mPEG products by liquid chromatography on reversed-phase monolithic silica-rods. Thus, we utilize fine, in-house prepared and narrow dispersity mPEGs (Ð ≤ 1.1) and commercial PEGdiol standards as a reference. Most efficient analysis of diol impurities becomes possible with reversed-phase liquid chromatography that results in selective elution of the PEGdiol from mPEG macromolecule populations in partition/adsorption mode. We do this by a minimum selectivity of the population of macromolecules characterizing the narrow molar mass distributions of mPEG. Control experiments with intentionally added water at the start of the well-controlled mPEG synthesis via the living anionic ring opening polymerization of ethylene oxide clearly reconciled the existence of PEGdiol impurity in chromatographed samples. The here-demonstrated methodology allows for the resolution of diol impurities of less than one percent in elution times of only a few minutes, confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) of the collected elution fractions. The unique combination of the open flow-through pore structure of the monolithic silica rods and resultant varying accessibility of C18-derivatized pore surfaces indicates beneficial properties for robust and end-group-specific adsorption/partition liquid chromatography of synthetic macromolecules.

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<p>A large fraction of organic matter in natural aqueous soil solutions is given by molecules in sizes above one nanometer, which classifies them as colloids according to the IUPAC definition. Such colloids feature discernable mobility in soils and their transport is decisive for the cycling of carbon as well as the migration of nutrients or contaminants. Yet, their size-dependent hydrodynamics and functional diversity result in transport phenomena that are specific to colloids and, thus, largely differ from those observed for smaller substances. Still, tracers that appropriately represent small organic colloids are not available and the investigation of their transport in laboratory column experiments, in dependence of size and chemistry, remains difficult. To overcome this limitation, we tested if well-defined synthetic polymers in the colloidal size range are suitable as non-conventional tracers of colloidal transport. As polymer backbone, we selected poly(ethylene glycol) (PEG) due to its high water-solubility and established pathway of synthesis that permits tailoring of functional moieties to the fullest extent. An easy and sensitive detection in the aqueous phase became possible by using a fluorophore as starting group. After full characterization, we studied PEG adsorption to quartz, illite, goethite, and their mixtures in batch and column transport experiments. In numerical simulations, we successfully reconstructed and predicted PEG transport based on its physicochemical as well as hydrodynamic properties and, thus, show that PEG transport can be comprehensively and quantitatively studied. Considering also its low adverse effect on the environment, functional PEG therefore presents as promising candidate to be used as organic tracer, designable in the size range of natural organic (macro-)molecules (Ritschel et al., 2021).</p><p>References</p><p>Ritschel, T., Lehmann, K., Brunzel, M., Vitz, J., Nischang, I., Schubert, U., Totsche, K. U. (2021) <strong>Well-defined poly(ethylene glycol) polymers as non-conventional reactive tracers of colloidal transport in porous media</strong>.<em> J. Colloid Interface Sci.</em> 548, 592-601, doi: 10.1016/j.jcis.2020.09.056.</p>