Prediction of Retention Indices in LC-HRMS for Enhanced Structural Identification of Organic Micropollutants in Water: Selectivity-Based Filtration.

Addressing the global challenge of ensuring access to safe drinking water, especially in developing countries, demands cost-effective, eco-friendly, and readily available technologies. The persistence, toxicity, and bioaccumulation potential of organic pollutants arising from various human activities pose substantial hurdles. While high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS) is a widely utilized technique for identifying pollutants in water, the multitude of structures for a single elemental composition complicates structural identification.

Physicochemical modelling of the retention mechanism of temperature-responsive polymeric columns for HPLC through machine learning algorithms.

Temperature-responsive liquid chromatography (TRLC) offers a promising alternative to reversed-phase liquid chromatography (RPLC) for environmentally friendly analytical techniques by utilizing pure water as a mobile phase, eliminating the need for harmful organic solvents. TRLC columns, packed with temperature-responsive polymers coupled to silica particles, exhibit a unique retention mechanism influenced by temperature-induced polymer hydration. An investigation of the physicochemical parameters driving separation at high and low temperatures is crucial for better column manufacturing and selectivity control.

Temperature-responsive comprehensive two-dimensional liquid chromatography coupled to high resolution mass spectrometry for the elucidation of the oxidative degradation processes of chemicals of environmental concern.

This study explores the possibilities offered by temperature-responsive liquid chromatography (TRLC) based comprehensive 2-dimensional liquid chromatography in combination with reversed-phase liquid chromatography (RPLC) for the analysis of degradation products formed upon oxidative treatment of persistent organic pollutants, in this case exemplified through carbamazepine (CBZ). The TRLC×RPLC combination offers the possibility to overcome peak overlap and incomplete separation encountered in 1D approaches, while the transfer of the purely aqueous mobile phase leads to refocusing of all analytes on the second dimension column. Consequently, this allows for about method-development free and hence, easier LC×LC.

Facilitating structural elucidation of small environmental solutes in RPLC-HRMS by retention index prediction.

Implementing effective environmental management strategies requires a comprehensive understanding of the chemical composition of environmental pollutants, particularly in complex mixtures. Utilizing innovative analytical techniques, such as high-resolution mass spectrometry and predictive retention index models, can provide valuable insights into the molecular structures of environmental contaminants. Liquid Chromatography-High-Resolution Mass Spectrometry is a powerful tool for the identification of isomeric structures in complex samples.

Hyphenating temperature gradient elution with refractive index detection through temperature-responsive liquid chromatography.

Refractive index detection (RID) is attractive because it allows approaching the benefits of universal detection with liquid chromatography, by which ideally standard independent calibration and hence compound independent quantification becomes possible. Nevertheless, the implementation of RID has remained limited as it offers poor detection sensitivity while only being compatible with isocratic mobile phases. The implementation of compositional solvent gradients has remained prohibitively challenging in commercial HPLC-RID systems due to the resulting drastic alterations in refractive index and extreme baseline drift.

Molecular weight distribution characterization of reactive higher ethyleneamines using size-exclusion chromatography with conventional calibration.

Ethyleneamines have been produced and commercialized for decades in the chemical industry for a diverse range of applications. The presence of amine functional groups provides them opportunity to adsorb onto surfaces which can make them a very challenging sample matrix to analyze using separation techniques. In the present report, a new aqueous SEC-RI method, which enables MWD characterization of higher ethyleneamines, is described.

Design and performance evaluation of a microfluidic ion-suppression module for anion-exchange chromatography.

A microfluidic membrane suppressor has been constructed to suppress ions of alkaline mobile-phases via an acid-base reaction across a sulfonated poly(tetrafluoroethylene)-based membrane and was evaluated for anion-exchange separations using conductivity detection. The membrane was clamped between two chip substrates, accommodating rectangular microchannels for the eluent and regenerant flow, respectively. Additionally, a clamp-on chip holder has been constructed which allows the alignment and stacking of different chip modules.

The axial rearrangement mixer: working principles and in-depth investigation.

In the current paper, an axial rearrangement mixer is studied. The mixer aims to flatten out occasional composition fluctuations originating from the pump. In a first phase, dispersion in a single mixer channel is investigated using pulses introduced by a dedicated injection pulse generator.

Performance evaluation of ion-exchange chromatography in capillary format.

The performance of a recently introduced capillary ion-exchange chromatography system was explored. Experiments were conducted in isocratic mode with a commercial capillary anion-exchange column (id = 0.4 mm, L = 15 cm) using a five-anion standard mixture.

Exploring the possibilities of cryogenic cooling in liquid chromatography for biological applications: a proof of principle.

The possibilities to use cryogenic cooling to trap components in liquid chromatography was investigated. In a first step, van 't Hoff plots were measured with a reversed-phase column using the temperature control unit of a conventional high performance liquid chromatography (HPLC) system to gain insight in the retention behavior of proteins at low temperatures. It was estimated that retention factors in the range of k = 10(4) could be achieved at T = -20 °C for lysozyme, indicating that temperature is a usable parameter to trap components in LC.

Performance evaluation of long monolithic silica capillary columns in gradient liquid chromatography using peptide mixtures.

A systematic study is reported on the performance of long monolithic capillary columns in gradient mode. Using a commercial nano-LC system, reversed-phase peptide separations obtained through UV-detection were conducted. The chromatographic performance, in terms of conditional peak capacity and peak productivity, was investigated for different gradient times (varying between 90 and 1320min) and different column lengths (0.

Design and evaluation of flow distributors for microfabricated pillar array columns.

Five different flow distributors have been compared as a function of the flow rate for their ability to distribute small sample volumes over the entire width of flat rectangular microfabricated pillar array columns. The investigated designs can be divided in two major categories: (1) bifurcating, radially non-interconnecting distributors and (2) radially interconnecting distributors consisting of diamond-shaped pillars, elongated in the direction perpendicular to the flow, providing a high ratio of radial permeability over axial permeability. The quality of the flow distribution was evaluated experimentally by injecting equal volumes of fluorescent tracer into each of the tested designs and calculating the obtained peak variances using the method of moments.

Use of non-porous pillar array columns for the separation of Pseudomonas pyoverdine siderophores as an example of a real-world biological sample.

We report on the first separation of a complex biomixture in pressure-driven mode using perfectly ordered pillar array columns. The separations were conducted in the reversed-phase mode using a highly aqueous mobile phase, while the outer surface of the non-porous pillars was chemically functionalized with a hydrophobic C8-layer. The samples originated from two different bacterial strains (Pseudomonas aeruginosa PAO1 and Pseudomonas sp.

Effect of the presence of an ordered micro-pillar array on the formation of silica monoliths.

We report on the synthesis of siloxane-based monoliths in the presence of a two-dimensional, perfectly ordered array of micro-pillars. Both methyltrimethoxysilane- and tetramethoxysilane-based monoliths were considered. The obtained structures were analyzed using scanning-electron microscopy and can be explained from the general theory of surface-directed phase separation in confined spaces.

Experimental investigation of the band broadening arising from short-range interchannel heterogeneities in chromatographic beds under the condition of identical external porosity.

The interesting possibilities offered by micropillar array columns to investigate the relation between bed heterogeneity and band broadening in chromatographic columns are illustrated and investigated. The perfect control over the microscopic bed structure offered by the photolithographic fabrication technique could be used to produce a heterogeneous bed displaying a short-range interchannel heterogeneity and having exactly the same particle size and external porosity as the perfectly ordered bed that was used as the reference system. According to this approach, any observed difference in band broadening could be directly owed to the effect of the bed heterogeneity.

Experimental investigation of the band broadening originating from the top and bottom walls in micromachined nonporous pillar array columns.

We report on the experimental investigation of the effect of the top and bottom wall plates in micromachined nonporous pillar array columns. It has been found that their presence yields an additional c-term type of band broadening that can make up a significant fraction of the total band broadening (at least if considering nonporous pillars and a nonretained tracer). Their presence also induces a clear (downward) shift of the optimal velocity.

Optimum kinetic performance of open-tubular separations in microfluidic devices.

A survey is made of the different factors contributing to the kinetic performance of open-tubular separation channels. Being representative for most of the channels used in microfluidic devices, the main focus is on channels with a rectangular format. Kinetic plots of t(0)/N(2 )versus N are established to allow for a visual selection of the ideal channel format and dimensions.

Pressure-driven reverse-phase liquid chromatography separations in ordered nonporous pillar array columns.

Building upon the micromachined column idea proposed by the group of Regnier in 1998, we report on the first high-resolution reversed-phase separations in micromachined pillar array columns under pressure-driven LC conditions. A three component mixture could be separated in 3 s using arrays of nonporous silicon pillars with a diameter of approximately 4.3 microm and an external porosity of 55%.

An automated injection system for sub-micron sized channels used in shear-driven-chromatography.

This paper describes a method to automatically and reproducibly inject sharply delimited sample plugs in the shallow (i.e., sub-micron) channels typically used in shear driven chromatography.