Thermal marks as a signal processing aid for a portable capillary electropherograph

Abstract

The interpretation of raw signals in capillary CE can be challenging if there are unknown peaks, or the signal is corrupt due to baseline fluctuations, EOF velocity drift, etc. Signal processing could be required before results can be interpreted. A suite of signal processing algorithms has been developed for CE data analysis, specifically for use in field experiments for the detection of nerve agents using portable CE instruments. Everything from baseline correction and electropherogram alignment to peak matching and identification is included in these programs. Baseline correction is achieved by interpolating a new baseline according to points found using all local extremes, by applying an appropriate outliers test. Irreproducible migration times are corrected by compensating for EOF drift, measured with the aid of thermal marks. Thermal marks are small disturbances in the capillary created by punctual heating that move with the velocity of EOF. Peaks in the sample electropherogram are identified using a fuzzy matching algorithm, by comparing peaks from the sample electropherogram to peaks from a reference electropherogram.

Qualitative and quantitative aspects of time‐, charge‐, and mobility‐based electropherograms

“…However, EOF can still impact both kinds of electropherograms. Therefore, the quest for EOF monitors, such as the thermal marks [26,27] or flow sensors [10], is important. Of course, having a stable EOF would be even better.…”

Providing Enhanced Migration Time Reproducibility with a High-Voltage-Compatible Flow Sensor for Capillary Electrophoresis

“…To account for these changes in the migration time, it is possible to use computerized time scale compensation in CE, which mainly focuses on peak mobility recalculation based on an EOF marker, internal standard reference, thermal time marks, or a two-step method. − Unfortunately, recalculation approaches fail in cases where EOF fluctuations are unpredictable and nonlinear . While thermal marks are capable of handling cases where the change of EOF velocity fluctuates, they introduce baseline distortion spikes that can interfere with the peaks of the analytes …”

“…11 While thermal marks are capable of handling cases where the change of EOF velocity fluctuates, they introduce baseline distortion spikes that can interfere with the peaks of the analytes. 12 In this publication, we describe how to continuously measure the flow and temperature inside the capillary during the separation to compensate for parasitic flow contributions and improve run-to-run reproducibly.…”

Fundamentos, produção e aplicações de marcas térmicas em eletroforese capilar

“…A partir desse trabalho, outro grupo de pesquisa publicou um artigo sobre a utilização de marcas térmicas para monitoramento de EOF em soluções de líquidos iônicos em meio não aquoso [38] e outro propondo um algoritmo para identificação de picos e correção de linha base do eletroferograma, utilizando as marcas térmicas para corrigir variações do EOF [39].…”