Polymerization of the through-pores in HPLC columns for enhanced SEM based assessment of packing order

Recent developments in chip-based column technology, whereby plate heights corresponding to the domain size can be obtained,[1] suggest that it might also be possible to improve the lower minimal plate height limit in packed column HPLC (h≈2dp), down to lower values if feasible improved packing procedures can be developed. In order to allow enhanced understanding of the order in packed HPLC columns, in this work a methodology for immobilizing silica particles is developed based on the polymerization of a monomer and a cross-linker in the interstitial pores of HPLC columns. Subsequent mechanical cutting allows scanning electron microscopy (SEM) based imaging of cross sections of the packed bed over the entire length of the column. In this way the packing efficiency of in-house packed and commercial HPLC columns comprising the same packing material can be compared. The methodology is developed for native silica used in e.g. hydrophilic interaction liquid chromatography and the information obtained is cross-referenced with external porosity measurements obtained via inversed size exclusion approach

Application of the isopycnic kinetic plot method for elucidating the potential of sub-2 micron and core/shell particles in SFC

One of the many advantages that Supercritical fluid chromatography (SFC) is attributed with over high performance liquid chromatography (HPLC) is that it should be possible to use longer columns and/or columns packed with smaller particles at higher velocities. This is due to the higher diffusivity of analytes in supercritical fluids compared to liquids (higher optimum mobile phase velocity) and to the lower viscosity of the mobile phases in SFC compared to HPLC (resulting in lower pressure drops over the column). In this work the isopycnic method to construct kinetic plots for SFC was used to investigate the performance limits of an SFC system when using sub- 2 µm fully porous particles and sub- 3 µm superficially porous particles. This isopycnic kinetic plot method for SFC was developed and tested earlier for SFC separations on bare silica with pure CO2 as mobile phase. In this work, C18 columns were used in combination with more realistic modifier amounts in the mobile phase in order to show the possibilities of measuring the performance of an SFC system as a function of flow rate for realistic chromatographic experimental conditions. Kinetic plot predictions were made for separations on 1 µm and 0.5 µm particles in order to examine the possibilities of working with these very small particles on the used SFC and HPLC systems

Hippocampal Sclerosis in Frontotemporal Dementia:When Vascular Pathology Meets Neurodegeneration

Hippocampal sclerosis (HS) is a common neuropathological finding and has been associated with advanced age, TDP-43 proteinopathy, and cerebrovascular pathology. We analyzed neuropathological data of an autopsy cohort of early-onset frontotemporal dementia patients. The study aimed to determine whether in this cohort HS was related to TDP-43 proteinopathy and whether additional factors could be identified. We examined the relationship between HS, proteinopathies in frontotemporal cortices and hippocampus, Alzheimer disease, cerebrovascular changes, and age. We confirmed a strong association between HS and hippocampal TDP-43, whereas there was a weaker association between HS and frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP). Nearly all of the FTLD-TDP cases had TDP-43 pathology in the hippocampus. HS was present in all FTLD-TDP type D cases, in 50% of the FTLD-TDP A cohort and in 6% of the FTLD-TDP B cohort. Our data also showed a significant association between HS and vascular changes. We reviewed the literature on HS and discuss possible pathophysiological mechanisms between TDP-43 pathology, cerebrovascular disease, and HS. Additionally, we introduced a quantitative neuronal cell count in CA1 to objectify the semiquantitative visual appreciation of HS.</p

Graphical Data Representation Methods To Assess The Quality of LC Columns

We discuss the most important plot types for the kinetic performance of liquid chromatography systems and elaborate on how these plots should best be constructed and can be made dimensionless. Distinction is made between plots that are most suited for practitioners (column users) versus those most suited for theoreticians and column manufacturers.status: publishe