Simplified universal method for determining electrolyte temperatures in a capillary electrophoresis instrument with forced‐air cooling

Abstract

Temperature increase due to resistive electrical heating is an inherent limitation of capillary electrophoresis (CE). Active cooling systems are used to decrease the temperature of the capillary, but their capacity is limited; and in addition, they leave "hot spots" at the detection interface and at the capillary ends. Until recently, the matter was complicated by the lack of a fast and generic method for temperature determination in efficiently and inefficiently cooled regions of the capillary. Our group recently introduced such a method, termed "Universal Method for determining Electrolyte Temperatures" (UMET). UMET is a probe-less approach that requires only measuring current versus voltage for different voltages and processing the data using an iterative algorithm. Here, we apply UMET to develop a Simplified Universal Method of Temperature Determination (SUMET) for a CE instrument with a forced-air cooling system using an Agilent 7100 CE instrument (Agilent Technologies, Saint Laurent, Quebec, Canada) as an example. We collected a wide set of empirical voltage-current data for a variety of buffers and capillary diameters. We further constructed empirical equations for temperature calculation in efficiently and inefficiently cooled parts of the capillary that require only the data from a single 1-min voltage-current measurement. The equations are specific for the Agilent 7100 CE instrument (Agilent Technologies) but can be applied to all kinds of capillaries and buffers. Similar SUMET approaches can be developed for other CE instruments with forced-air cooling using our approach.

Ideal‐filter capillary electrophoresis: A highly efficient partitioning method for selection of protein binders from oligonucleotide libraries

“…Increasing I BGE leads to greater Joule heat generation and increased temperature inside the capillary, T cap , that can lead to dissociation of target‐binder complexes . Timely, this limitation can be overcome with a recently introduced simplified universal method for predicting electrolyte temperatures (SUMET) which allows adjusting T cap to a desirable value by rationally lowering the electric field strength, E . Advantageously, increasing I BGE makes BGE more physiological and can allow selection of binders intended for use in vivo (e.g., as detection probes, drugs, or drug‐delivery vehicles).…”

Optimization of affinity capillary electrophoresis for routine investigations of protein–metal ion interactions

“…The inlet and outlet (inefficiently cooled parts) of the capillary are out of the cooling system. The temperature was determined in different parts across the whole capillary length and found to be up to 15 degrees higher in inlet region (inefficiently cooled) than in the efficiently cooled parts, depending on power per unit volt . It is well known that, the lengths of the inefficiently cooled parts are different from CE instrument to another, thus the overall capillary temperature of each instrument can vary.…”

A simple method for assessment and minimization of errors in determination of electrophoretic or electroosmotic mobilities and velocities associated with the axial electric field distortion

“…These three parts are devoid of an efficient heat exchange and thus produce an extensive Joule heating after application of voltage . It was demonstrated by Xuan and Li and more recently by Krylov's group , that nonuniform heat dissipation throughout the capillary entails an axial electric field distortion, correlated with a difference in temperature between the cooled and noncooled parts of capillary. Owing to the fact that in the warmer capillary parts the current conductivity is increased, the electric field potential has to be simultaneously lowered to satisfy the requirement of current continuity.…”

“…Xuan and Li proposed the theoretical model allowing to predict the distortion of electric field, resultant pressure gradient, and the local velocities in different capillary parts . Krylov's group, in turn, invented the methods allowing to estimate a difference in temperature between cooled and noncooled capillary parts, and thereby the magnitude of electric field distortion, on the basis of multiple current and voltage measurements . However, the field distortion‐associated errors in determination of electrophoretic or electroosmotic mobilities, and the related changes of axial velocities were not investigated experimentally till now.…”