Automated Biomonitors For Toxins Based On Potentiometric Detection Of Carbon Dioxide.

The selectivity characteristics of pCO(,2) sensors using different gas permeable membrane materials are examined. The development of an automated CO(,2) gas sensing system is described. Applications of this system as a biomonitor to screen for toxic substances are presented. The feasibility of utilizing the biomonitor concept as a sensitive detector for liquid chromatography is also discussed. The response of pCO(,2) sensors with regard to various organic and inorganic acid interferents has been studied. In addition, various gas permeable membranes were examined in an attempt to enhance the selectivity of the sensor. Alternate methods to reduce organic acid interferents were also investigated and are discussed. The new automated CO(,2) sensing system utilizes a flowing electrolyte stream in conjunction with a gas dialyzer unit. A flow-through polymer pH electrode is employed for potentiometric detection. Parametric studies were performed and the system optimized for Nernstian response between 2 x 10('-4) M and 1 x 10('-3) M CO(,2). Several applications of the automated CO(,2) sensor as a biomonitor to rapidly screen for toxins are presented. Biocatalytic activity is detected by measuring the amount of CO(,2) liberated from a biocatalytic reaction. Toxins decrease the activity of the biocatalyst resulting in less CO(,2) being produced. A rapid screen for heavy metals is presented using the enzyme urease which directly catalyzes the production of CO(,2). Acetylcholinesterase was utilized as an example of a system which indirectly catalyses the production of CO(,2). This system provides a sensitive screen for pesticides. The respiration of living cells has also been monitored with this CO(,2) sensing system. The inhibition of the respiration of Escherichia coli by several antibiotics is presented. The feasibility of employing the biomonitor concept as a detector for liquid chromatography is also examined. The urea/urease biomonitor is utilized in conjunction with ion-pair chromatography. In this arrangement, the sample is separated on a column prior to introduction into the biomonitor, thus, allowing the identification and quantitation of the sample components.Ph.D.Analytical chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/127785/2/8521017.pd