Longitudinal diffusion and resistance to mass transfer as causes of nonideality in chromatography

In modeling subsurface contaminant transport, sorption is often simplified by assuming instantaneous equilibrium, isotherm linearity, and sorption‐desorption singularity. Data exhibiting behavior that deviates from that predicted by this simple model have been reported, challenging the validity of these assumptions. This nonideal sorptive behavior has been attributed to several different factors, including kinetic sorption reactions, diffusive mass transfer resistances, isotherm nonlinearity, and sorption‐desorption nonsingularity. These factors are examined and their relative impact on contaminant transport is evaluated. For hydrophobic organic compounds, physical nonequilibrium (i.e., rate‐limited mass‐transfer in aggregated or layered systems) and intraorganic matter diffusion (rate‐limited diffusion within the sorbent organic matter matrix) are probably the predominant factors causing nonideality. The relative importance of these factors is scale‐dependent. For smaller scale systems, mass‐transfer lim...

Sorption nonideality during organic contaminant transport in porous media

Preparative liquid chromatography.

Publisher Summary This chapter describes the fundamental aspects of gel chromatography as they comprise a set of analytical techniques that a protein chemist may use. The unifying principles that underlie these techniques have been a major focus of interest. The chapter focuses on the two fundamental principles that underlie the use of gel chromatographic systems as analytical tools in protein chemistry: (1) partition coefficients depend on molecular size and shape in contrast to surface or charge properties. (2) Gel columns are linear chromatographic systems and can, therefore, be used for the analysis of nonlinear molecular phenomena such as those occurring in chemically reacting multicomponent systems. Although deviations from these two principles of ideal behavior are almost always present, their magnitude is almost always small. In addition, it is evident on both theoretical and experimental grounds that the group of techniques based on the partitioning of molecules into porous gel networks constitutes an extremely versatile and useful array of analytical tools for the studies of protein systems. It may be expected, therefore, that the application of these techniques will be extended to a much wider group of experimental systems.

Analytical gel chromatography of proteins.

In this work, we report a cathodic electrogenerated chemiluminescence (ECL) of luminol at a positive potential (ca. 0.05 V vs Ag/AgCl) with a strong light emission on the graphene-modified glass carbon electrode. The resulted graphene-modified electrode offers an excellent platform for high-performance biosensing applications. On the basis of the cathodic ECL signal of luminol on the graphene-modified electrode, an ECL sandwich immunosensor for sensitive detection of cancer biomarkers at low potential was developed with a multiple signal amplification strategy from functionalized graphene and gold nanorods multilabeled with glucose oxidase (GOx) and secondary antibody (Ab2). The functionalized graphene improved the electron transfer on the electrode interface and was employed to attach the primary antibody (Ab1) due to it large surface area. The gold nanorods were not only used as carriers of secondary antibody (Ab2) and GOx but also catalyzed the ECL reaction of luminol, which further amplified the ECL s...

Positive Potential Operation of a Cathodic Electrogenerated Chemiluminescence Immunosensor Based on Luminol and Graphene for Cancer Biomarker Detection

J. Norton Wilson

Papers

A Theory of Chromatography

Measurement of a Reaction Rate at Equilibrium by Means of a Radioactive Indicator. The Reaction between Arsenic Acid and Iodine

An Attempted Exchange of Phosphorus between Phosphorous and Phosphoric Acids

The Addition Reaction of Phosphorus Trifluoride with Chlorine

Thermal and Photochemical Exchange Reactions of Bromine