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Browsing by Author "Dressen, Brian M., author"

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    Development of a microchip electrophoresis environmental monitoring system: from surface to separation chemistry
    (Colorado State University. Libraries, 2008) Dressen, Brian M., author; Henry, Charles S., advisor
    Environmental contaminants are an increasing problem in today's modern world. Methods of incorporation into the human body are numerous, but perhaps the most common is ingestion with food or drinking water. Of more recent concern is perchlorate in drinking water. Human exposure to perchlorate is of concern because of the potential for impaired thyroid function, leading to a number of developmental delays and other medical problems. Its prevalence in the environment only gained interest in the late 1990's, once a method was developed for its detection at the 4 ppb level. In 2005 after being added to the Environmental Protection Agency's (EPA) Unregulated Contaminant Monitoring Rule (UCMR1) list, a sampling of 2800 large water systems and 800 smaller systems, representing less than 10% of all US water systems, revealed contamination in 153 sites over 25 states. Numerous methods of analysis exist relying on expensive bench-top analysis devices that require long analysis times. This dissertation details the development of a perchlorate sensor capable of sub ppb detection limits and 4 min analysis times, with a total cost of less than $10K. The size of the sensor device and supporting equipment lends itself to portability for near-real-time in-field monitoring. This device combines microchip capillary electrophoresis with sensitive detection technology to reliably separate and detect perchlorate in surface and waste water samples. Here I describe the comprehensive development of the microchip system including control of surface chemistry, flow magnitude and direction, bulk material selection, and chemical selectivity to allow for the separation of perchlorate in water. Optimization of the microchip system, including the use of a selective zwitterionic surfactant to enhance on-chip separations is also presented. The final outcome of this dissertation work is a near-portable environmental sensor for perchlorate capable of meeting EPA regulations for sensitivity to perchlorate as well as several advances in controlling the chemistry within microchip electrophoresis devices through modification or bulk material selection.