Development and Application of Automated Ammonia Gas Sensing Systems Based on Polymer Membrane Electrodes.

An automated electrode-based system for the rapid determination of ammonia gas in the 10('-6) to 10('-3) mol/L range is described. The system designed utilizes a novel tubular flow-through PVC-Nonactin polymer membrane electrode to sense ammonium ions formed in a flowing internal electrolyte stream as the sample passes through a gas dialysis chamber. Thorough investigations regarding the optimization of system variables such as flow rates, diluent reagents, segmentation, etc. are described. Studies concerning the selectivity of this newly devised ammonia gas sensing system toward various volatile amines are also presented. Chapter II describes the application of the automated system for the direct determination of ammonia-N in blood samples. Peak potentials observed are logarithmically related to sample ammonia-N concentrations. In Chapter III an automated enzymatic assay system for the direct determination of amino acids in blood is described. This system utilizes a unique on-line predialysis unit which nondestructively and efficiently removes interferent background levels of ammonia-N from physiological samples prior to the enzymatic step. The clinical application of the system is demonstrated via the direct measurement of L-asparagine in plasma samples through the use of the enzyme L-asparaginase. Peak potentials observed are logarithmically related to the amino acid concentration. With the systems described in Chapters II and III, at least 30 samples/h can be assayed with excellent precision and accuracy in the normal blood ammonia-N or amino acid range. In Chapter IV attempts to construct an automated toxicity biomonitor capable of screening for toxic substances in aqueous environmental samples is described. The reagents used as the biological indicators are ammonia producing or assimilating biocatalysts. Toxic substances are detected by their in-situ inhibitory effect on the ammonia producing or assimilating ability of the biocatalyst used. Preliminary data from a variety of enzyme and bacterial systems exposed to toxic water soluble organic and inorganic compounds are presented. Chapter V is a general summary of Chapters II, III, and IV as to goals sought, achieved and possibilities for further improvements.PhDAnalytical chemistryUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/159181/1/8304491.pd