The development of analytical instrument based on isotachophoresis (ITP) for measuring cations in aqueous samples

Makas, Agata (2025) The development of analytical instrument based on isotachophoresis (ITP) for measuring cations in aqueous samples. PhD thesis, Lancaster University.

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Abstract

Isotachophoresis (ITP) has been investigated as a potential on-line instrument to measure water quality in the industry. The project focused on the ions responsible for water hardness (Ca2+ and Mg2+) and toxic metals ions (Cr3+, Al3+, Cu2+, Fe2+ and Pb2+) and ammonium ion. The choice of ions was made by the sponsor company Process Instruments Ltd, which was looking to design the prototype instrument based on ITP separation. Isotachophoresis was a novel analytical technique used in water hardness determination. A number of methods from the literature were evaluated and were studied further. That included preparation of calibration graphs which were used in calculations of the ions concentrations, experiments at various pH of the electrolytes, comparison of the results with conventional separation techniques such as: ion chromatography (IC) and inductively coupled – optical emission spectrometry (ICP-OES). The number of samples analysed was: 8 samples of commonly available bottled water and 13 tap water samples from around the Europe, including samples from: Poland. Greece, France, Turkey and many locations in the UK. In the project nine different ITP electrolyte systems were investigated, number of them allowed separation of multiple ions of interest. ICP-OES experiments included analysis of samples at various wavelengths (each element was analysed at 6-12 different wavelengths). IC column available at the university only allowed separation of calcium, magnesium and ammonium ions. The final stage of the project included design and construction of the prototype instrument. In the end it was possible to construct the prototype of instrument based on ITP separation. The system was set up using parts widely available in every laboratory, syringes, plastic tubing and platinum wire. It reused the power supply which was used in different projects. The detector was designed and made by the supervisor especially for this project. The prototype has been proven to be working by the separation of the anionic dyes, bromophenol blue and amaranth using electrolytes system consisting of leading electrolyte: 10mM HCl, 0.05% Mowiol, pH 6.0 (adjusted by histidine) and terminating electrolyte: 10mM MES, pH 6.0 (adjusted by histidine) with applied voltage of 3500V. Unfortunately the timescale of the project prevented further optimisation and evaluation of the prototype, it left the exciting part of the process for the sponsor company.