Characterization of polyoxyethylenes according to the number of hydroxy end groups by hydrophilic interaction chromatography at critical conditions for polyethylene glycol

PolyCrit: An Online Collaborative Platform for Polymer Characterization

Polymer liquid chromatography at critical conditions (LCCC) is a chromatographic separation condition achieved by carefully balancing the interaction of a polymer with stationary and mobile phases to make the elution time of a polymer in chromatography independent of its molecular weight. By removing the dependence of elution time on polymer molecular weight, the LCCC then allows separation of polymer samples on the basis of secondary differences, such as topology, branching, and end-group functionality, that are otherwise difficult to resolve. Despite its potential, LCCC remains under-employed due to the complexity of its optimization and the scattered nature of existing data. To address these challenges, we developed PolyCrit, a database that organizes 428 critical chromatography conditions (characterized by 33 parameters) into a searchable and accessible online platform. PolyCrit centralizes decades of literature, providing detailed information on polymers, solvents, stationary phases, and chromatographic parameters. It features a quality scoring system to ensure data reliability and supports contributions from the research community through a validation process. By curating experimental critical conditions, PolyCrit reduces the need for extensive literature searches to utilize the powerful chromatographic technique. Additionally, PolyCrit invites current researchers to contribute to the database by submitting their own work. It can be found at https://lccc.ywangcomp.org.

Controlling the positive ion electrospray ionization of poly(ethylene glycols) when using ultra-high-performance supercritical fluid chromatography-mass spectrometry

Poly(ethylene glycols) are complex polymers often added to pharmaceutical formulations to improve drug solubility and delivery. One of the main challenges when using chromatographic techniques coupled to mass spectrometry is the unselective ionization of poly(ethylene glycols) oligomers. Additionally, when the chain length is large enough, multiple charged species are formed, further complicating the mass spectra and processing. This study uses the advanced oligomer separation provided by supercritical fluid chromatography with a mass spectrometry approach that selectively ionizes poly(ethylene glycols) as ammoniated molecules to simplify data analysis and facilitate batch-to-batch comparisons. Several visual representations of the response of the ionization events based on the polymer molecular weight and the repeating unit were used to elucidate trends in ionization. Evaluation of the influence of the oligomer length and end-group on the electrospray ionization of the polymer allowed the development of a process to enable selective ionization for these complex polymers.

Fast determination of functionality-type × molecular-weight distribution of propoxylates with varying numbers of hydroxyl end-groups using gradient-normal-phase liquid chromatography × ultra-high pressure size-exclusion chromatography

Understanding the relation between chemical characteristics and properties of synthetic polymers is one of the challenges faced by analytical chemists in industry. This is a complex task, as polymers are not synthesized as single molecule, but are populations of chemically similar compounds with distributions over several properties. The latter include, for example, molecular weight, nature of end-groups (functionality), and chemical composition. In this paper, comprehensive two-dimensional liquid chromatography was used to determine the combined functionality-type and molecular-weight distributions of hydroxy‑functionalized propoxylates. Propoxylates derived from different initiators (one up to eight terminal hydroxyl groups) were separated in the first dimension using a gradient normal-phase LC separation (NPLC). In the second dimension ultra-high pressure size-exclusion chromatography separation (UHPSEC), further speciating distributions based on molecular size. The developed NPLC × SEC method with evaporative light-scattering detection can be used for the fast screening (< 30 min) of mutually dependent functionality-type and molecular-weight distributions of unknown propoxylates.

Fast Screening of Diol Impurities in Methoxy Poly(Ethylene Glycol)s (mPEG)s by Liquid Chromatography on Monolithic Silica Rods

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.

Characterization of Tween® Surfactants by MALDI TOF-MS and High Performance Liquid Chromatography in a Ternary Mobile Phase

Different hydrophobic and hydrophilic functionalities are produced in the reaction mixture of Tween® surfactants which affect the physiochemical properties of the final product. Only hydrophilic fractions and monoesters were separated in the binary mobile phase. MALDI TOF-MS of Tween® 40 revealed the identification of peaks separated in binary mobile phase (methanol-water). Liquid adsorption chromatography was performed on a gradient system on a SynergiTM fusion reverse phase column. Mobile phase composition used for this separation was a ternary phase gradient starting from 41 % methanol, 47 % acetone and going to 96 % acetone for the analysis time of 60 minutes. In the ternary mobile phase, gradient all the species such as polyethylene glycol, sorbitan and isosorbide ethoxylates, mono-, di- and triesters of sorbitan and isosorbide ethoxylates were well resolved in an of 60 minutes analysis time. The above separation mechanism can be employed for the analysis of polymeric multifunctional surfactant compositions.

Amine-selective affinity resins based on pH-sensitive reversible formation of covalent bonds

A new class of affinity resins using reversible covalent bonds is introduced for the separation of amine-containing molecules. pH-sensitive reversible formation of amic acid bonds between amines and carboxylate dimethyl maleic anhydride-decorated wrinkled silica nanoparticle resins was used to selectively retain and release amine-containing molecules, by controlling the pH.