Analyte migration electrospray ionization for rapid analysis of complex samples with small volume using mass spectrometry

Complex biological matrices can be effectively removed in the analyte migration process because of their weak solubility in organic solvents.

Quantitative description of analyte migration behavior based on the dynamic complexation model in capillary electrophoresis

A theory based on dynamic complexation is used to describe analyte migration behavior in capillary electrophoresis (CE). This theory is based on a one-phase system, instead of the commonly accepted two-phase system. The migration behavior of an analyte is described by three parameters (the electrophoretic mobility of the free analyte, the electrophoretic mobility of the analyte–additive complex, and the equilibrium constant (formation constant) that determines the fractions of the free analyte and the complex at a certain additive concentration). Varying the additive concentration shifts the equilibrium and changes the viscosity of the background electrolyte. Viscosity correction is crucial in interpreting the observed migration behavior of analytes. While electroosmotic flow in a capillary often varies from one capillary to another, the viscosity of a buffer is characteristic of the buffer composition and is constant for each buffer. The electrophoretic mobility of a certain species and the equilibrium constant are intrinsic properties and are less sensitive to changes in the environment. Understanding these relationships is indispensable in CE method development and method validation. A universal resolution equation is proposed, with a separation factor that has taken both the electrophoretic mobilities and equilibria into consideration. This resolution equation gives clear guidance for the optimization of CE separations. A group of nucleosides and their phosphates are used as analytes, and β-cyclodextrin is used as the additive in the model system studied in this paper. Both the observed analyte migration behavior and the resolution of analytes agree well with this theory. Keywords: dynamic complexation capillary electrophoresis, nucleoside and nucleotide separation, capacity factor, resolution equation, viscosity correction.

Rutherford Backscattering Spectrometry Investigation of the Permeability of Pyrolytically Coated Graphite Substrates

Rutherford backscattering spectrometry (RBS) and scanning electron microscopy (SEM) were used to investigate the interactions of analytes with pyrolytically coated graphite, which is typically used in graphite furnace atomic absorption spectrometry (GFAAS). Chemical species were found to migrate into the bulk of the graphite, up to depths of at least 3 μm, when deposited in a solution form on a nontreated or an oxygen-pretreated graphite flat. Because this migration was not observed when the analyte was deposited by vapor deposition or laser ablation, we conclude that the analyte migration proceeds via capillary action, as in the case of polycrystalline graphite. Pretreatment of the graphite flat with hydrogen prevented migration of the analytes into the bulk of the graphite when they were deposited in solution form.