Performance and lifetime of slurry packed capillary columns for high performance liquid chromatography

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Because of its high conductivity when acid doped, polyaniline is known as a synthetic metal and is used in a wide range of applications, such as supercapacitors, biosensors, electrochromic devices, or solar and fuel cells. Emeraldine is the partly oxidized, stable form of polyaniline, consisting of alternating diaminobenzenoid and iminoquinoid segments. When acidified, the nitrogen atoms of emeraldine become protonated. Due to electrostatic repulsion between positive charges, the polarity and morphology of emeraldine chains presumably change; however, the protonation effects on emeraldine have not yet been clarified. Thus, we investigated these changes by reversed-phase capillary liquid chromatography using a linear solvation energy relationship approach to assess differences in dominant retention interactions under a significantly varied mobile phase pH. We observed that hydrophobicity dominates the intermolecular interactions under both acidic and alkaline eluent conditions, albeit to different extents. Therefore, by tuning the mobile phase pH, we can even modulate the retention of neutral hydrophobic solutes, such as aromatic hydrocarbons, because the pH-dependent charge and structure of polymer chains of the emeraldine-coated silica stationary phase show a mixed-mode separation mechanism.

Section: Methodsmentioning

confidence: 99%

Protonation of polyaniline‐coated silica stationary phase affects the retention behavior of neutral hydrophobic solutes in reversed‐phase capillary liquid chromatography

Taraba

Křížek

Kozlík

et al. 2018

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“…Then the union was connected to the capillary. The packing procedure was based on the work of Franc et al [39]. The prepared stationary phase was suspended in 50% methanol v/v acting as the slurry solvent to obtain a slurry concentration of 0.02 g/mL.…”

Section: Slurry Packing Proceduresmentioning

confidence: 99%

Characterization of polyaniline‐coated stationary phases by using the linear solvation energy relationship in the hydrophilic interaction liquid chromatography mode using capillary liquid chromatography

Taraba

Křížek

Hodek

et al. 2016

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A polyaniline coating was used to modify the surface of bare silica gel and octadecyl silica stationary phases to characterize the properties of altered materials. It was assumed that the mixed-mode retention was established on the basis of the polyaniline chemical structure and its combination with the original sorbents. Polyaniline was deposited onto the original surfaces during the chemical polymerization of aniline hydrochloride. The prepared materials were slurry packed into capillary columns and systematic chromatographic characterization was performed using the linear solvation energy relationship, also employing descriptors that allow inclusion of ionic interactions in the proposed retention mechanism. The retention times of 80 solutes with various chemical structures were measured in the hydrophilic interaction liquid chromatography mode. The obtained results demonstrated the significant contribution of the polyaniline coating to the retention mechanism under the given conditions; the assumed mixed-mode retention was confirmed. The dominant retention interaction for both modified stationary phases was based on the protonation of nitrogen atoms in the polyaniline structure, leading to suitable retention and selectivity for the hydrophilic analytes, especially anionic and zwitterionic species. Thus, especially, the polyaniline-coated bare silica gel sorbent seems to be promising for potential applications related to the separation of polar compounds.

“…This frit retains the stationary phase particles inside the capillary. While the packing process itself is very simple, there are a number of parameters, such as packing pressure, packing time, and the use of sonication, that can influence the resulting column performance, as shown in our previous work . One of these parameters is the type of the outlet frit.…”

Section: Introductionmentioning

confidence: 96%

Comparison of different types of outlet frits in slurry‐packed capillary columns

Franc

Sobotníková

Coufal

et al. 2014

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Fused-silica capillary columns for high-performance liquid chromatography with 320 and 250 μm inner diameter were prepared by slurry packing with 5 and 3 μm Nucleosil C18 stationary phase. Different types of mechanical and monolithic outlet frits were used and their influence on the resulting column performance was evaluated. Columns with quartz wool exhibited symmetrical peaks and low theoretical plate height, and the preparation time was short. The performance of monolithic frits varied based on type of monolith, length of the frit, and silanization procedure. The best frit performed similarly to the quartz wool ones, but the preparation took several hours. Their main advantage lies in the possibility of on-column detection, because the detection window can be burnt immediately behind the frit.