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Development of a contactless conductivity detector for capillary zone electrophoresis
KTH, School of Chemical Science and Engineering (CHE).
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Utveckling av en kontaktfri konduktivitetsdetektor för kapillärzonelektrofores (Swedish)
Abstract [en]

In this project a contactless conductivity detector for capillary zone electrophoresis has been developed together with control programs to quantify the measured signals. Direct detection techniques, like conductivity detection, are often more preferred due to lower limits of detection and higher probability of detecting the analyte of interest compared to indirect optical detection. In contactless conductivity detection a high frequency signal is applied to a working electrode placed on the outside of the capillary and the generated electric current is measured at the measurement electrode. The signals are then further processed in order to generate an electropherogram. The components constructed in this work consist of a detection cell, an electronic circuit and a program to generate electropherograms.The detection cell consists of two 4 mm thick copper electrodes separated by 1.2 mm. A hole with 375 µm diameter was drilled through the electrodes where the capillary is inserted. The electronic circuit converts the generated currents to voltages that can be read by a microprocessor.

A linear relationship was seen between the mean output voltages read by the analog to digital converter and different resistances tested (R2 = 0.992 for 18 data points). A similar study was performed with di-potassium phosphate of six concentrations ranging from 1 to 50 mM of and a linear regression showed an R2 – value of 0.954. The currents generated through the capillary were registered using a potentiostat. A frequency study showed no optimal value where the amplitude of the generated currents was increased due to a frequency dependent amplitude. The limit of detection for sodium and lithium ions was determined to 15 and 45 µM respectively, whereas the limit of detection for glucose and galactose was determined to 400 and 500 µM respectively. A linearity range study for glucose showed a linear correlation between the normalised areas and the injected concentrations.

Place, publisher, year, edition, pages
2014.
Keyword [en]
Contactless conductivity detector, capillary electrophoresis, detection cell, monosaccharides, inorganic cations
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-159165OAI: oai:DiVA.org:kth-159165DiVA: diva2:782768
Available from: 2015-01-22 Created: 2015-01-22 Last updated: 2017-08-31Bibliographically approved

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