Fundamental and Applied Studies of Electrochemical Methods for the Detection of Polyanion and Polycation Species.

[摘要] Potentiometric polyion sensors have many advantages and potentially important applications in the clinical/biomedical field.Although conventional polyion sensors have been applied for detecting a wide range of polyionic analytes and enzymes that can depolymerize these species, they are essentially single-use devices, which limit broader applications, especially in automated flow-through analytical methods.Within the last ten years, reversible chronopotentiometric polyion sensors (pulstrode) have been developed to overcome limitations of single-use devices.In this thesis, further mechanistic studies and a quality control application of single-use polyion sensors are examined, and additional development and novel applications of newer pulstrode type polyion sensor systems are reported. First, the mechanism of potentiometric response of the single-use polyanion sensor is re-examined.Using fractionated heparin void of low molecular weight heparins, the extraction and transport of macromolecular heparin intothe polymer membrane of the sensor as a complex with tridodecylmethylammonium ion is reconfirmed, and diffusion coefficients of 2.7x10-9 cm2s-1 ± 0.27 for the complex are found.Such polyanion sensors are then employed in detecting the presence of oversulfated chondroitin sulfate (OSCS) contaminant/adulterant in commercially available lots of heparin from Baxter, Inc. Results using the polyanion sensor are found to correlate 100% with NMR data.In the second portion of this research, a reversible pulstrode type polyion sensor is applied to study three different systems.The pulstrode is utilized for the first time as a detector in flow-injection analysis (FIA).The system is capable of measuring both polycations and polyanions in the 10-100 µg/mL and 40-200 µg/mL range, respectively, using the same sensor/membrane formulation with a sample throughput of up to 20 samples/h.Pulstrode is also employed in monitoring enzymatic reactions, where hexametaphosphate/acid phosphatase is used as a model substrate/enzyme system.The rate of reversal in potentiometric polyanion signal indicates rate of digestion of the polyanionic substrate, hexametaphosphate, and hence the amount of enzyme activity present.Lastly, the pulstrode’s parameters (current pulse magnitude, etc.) are optimized to improve the detection limits in the application of this sensor to detect high charge density contaminants in heparin preparations, achieving an LOD of 2 wt% for pentosan polysulfate in heparin.

[发布机构] University of Michigan

[效力级别] Potentiometry and Chronopotentiometry

[关键词] Electrochemistry;Potentiometry and Chronopotentiometry;Polymeric Membrane Based Sensors;Polyanion and Polycation Detection;Chemistry;Science;Chemistry