Conductivity detection on microchips.

Roland Hergenröder; Benedikt Grass

doi:10.1385/1-59745-076-6:113

Home/Archive/PubMed

PubMed · 16790870

Conductivity detection on microchips.

Roland Hergenröder·Benedikt Grass

View original source ↗Export metadata ↓

Abstract

Conductivity detection as a versatile detection technique for chip-based electrophoretic separation methods is described and the basic principles are discussed. The necessary electronic equipment and technologies to implement the detection electrodes on a microchip are presented. A difference between contact and contactless detection is made and the resulting advantages and problems are shown. Different analytical applications are listed and discussed that show the basic applicability of conductivity detection in capillary electrophoresis and in isotachophoresis, which may serve as a guideline for more specific developments in the future. Central to all applications is the choice of the buffer system. It determines not only the separation capability but also puts limits on the achievable dynamic detection range.

Explore related subjects

Buffers Electric Conductivity Electrochemistry Electrodes Electrophoresis, Microchip Equipment Design Polymethyl Methacrylate Journal Article

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Roland Hergenröder, Benedikt Grass. 2006. Conductivity detection on microchips.. https://doi.org/10.1385/1-59745-076-6%3A113

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Differential ionic permeation of DNA-modified electrodes.

Ionic permselectivity of DNA films has been investigated by the analysis of the electrochemical response of methylene blue (MB) as a function of pH and ionic strength on DNA-modified electrodes in aqueous p-nitrophenol (p-NP) and phosphate buffers. We have observed a linear Pourbaix diagram in p-NP buffer indicating that the reduction of MB occurs with a two-electron plus one-proton reaction. Interestingly, in phosphate buffer the Pourbaix diagram is curved and this suggests that the thermodynamics of MB incorporated in the film depend also on the ratio of mono- versus divalent anions in the bulk. This result indicates that DNA films do not behave as pure ion-exclusion films, but instead there is a differential permselectivity that depends on the identity of the anions. Based on this consideration of the ionic distribution in the films, we provide a new method for the analysis of the DNA surface coverage based on AC impedance of an anionic species, ferricyanide. The methodology is of particular value in analyzing DNA hybridization and dehybridization. This approach presents an advantage compared to standard ruthenium hexammine assays since our methodology is insensitive to film morphology, and is highly sensitive to the amount of negative charge on the surface.

Buffers↗

PubMed2007

Assessing the peak capacity of IMS-IMS separations of tryptic peptide ions in He at 300 K.

Two-dimensional ion mobility spectrometry (IMS-IMS) coupled with mass spectrometry is examined as a means of separating mixtures of tryptic peptides (from myoglobin and hemoglobin). In this study, we utilize two distinct drift regions that are identical in that each contains He buffer gas at 300 K. The two-dimensional advantage is realized by changing the structures of the ions. As ions arrive at the end of the first drift region, those of a specified mobility are selected, exposed to energizing collisions, and then introduced into a second drift region. Upon collisional activation, some ions undergo structural transitions, leading to substantial changes in their mobilities; others undergo only slight (or no) mobility changes. Examination of peak positions and shapes for peptides that are separated in the first IMS dimension indicates experimental peak capacities ranging from approximately 60 to 80; the peak shapes and range of changes in mobility that are observed in the second drift region (after activation) indicate a capacity enhancement ranging from a factor of approximately 7 to 17. Thus, experimental (and theoretical) evaluation of the peak capacity of IMS-IMS operated in this fashion indicates that capacities of approximately 480 to 1360 are accessible for peptides. Molecular modeling techniques are used to simulate the range of structural changes that would be expected for tryptic peptide ions and are consistent with the experimental shifts that are observed.

Buffers↗

PubMed2007

Determination of nitrobenzene by differential pulse voltammetry and its application in wastewater analysis.

A new method for the determination of nitrobenzene (NB) by differential pulse voltammetry (DPV) based on an adsorptive stripping technique was developed. Cyclic voltammetry (CV) was used in a comparative investigation into the electrochemical reduction of NB at a glassy carbon electrode (GCE). With this electrode, the sharp peak of NB appeared at -0.71 V (vs. Ag/AgCl). The experimental parameters were optimized. Studies on the effect of pH on the peak height and peak potential were carried out over the pH range ca. 9.0-11.5 with sodium carbonate/sodium hydrogen carbonate buffer solution. A solution of pH 9.9 was chosen as analytical medium. Cathodic peak currents were found to be linearly related to the concentration of NB over the range ca. 12.3-1.23 x 10(4) microg L(-1) with relative standard deviations of ca. 3.26-6.75%. The detection limit of NB in water was 5.42 microg L(-1). The interference of organic and inorganic species on the voltammetric response was also studied. The proposed method was applied to the determination of NB in wastewater samples with an average recovery of ca. 95.9-102.4%.

Buffers↗