The kinetic phosphorlmeiric determination of uranyl Ion in aqueous solutions at room temperature yielded a detection limit for UOz2+ of 1 ng/L. The response to uranlum Is linear from the detection ilmH up to 5 mg/L. The method Is fast and accurate, with no separative pretreatment needed for most of the real samples investlgated. I n the anaiysls of bloioglcai samples, wet-ashlng with HNO3/HzO2 Is requlred for measurements near the detection ilmlt. Samples with uranium concentrations hlgher than 0.1 pg/L gave relatlve standard devlations typically below 5 %. Factors affecting the quantum yield of the uranyl Ion phosphorescence, e.g. quenchlng from specles present In the matrix, are accounted for in the klnetlc analysis of the uranyl phosphorescence.

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Determination of NH3 in flowing N2 or air Is demonstrated by monitoring changes in the photoconductivity of chlorolndlum phthalocyanine (InPc-CI) and chlorogalllum phthalocyanine (GaPc-CI) thin films vacuum deposited on platinum silicide Interdlgltated array microcircuits. Photoconductivity changes were measured, as opposed to the more commonly measured dark conductivity changes, yielding reasonable sensitivity to the adsorption of submonolayer amounts of gas analytes such as NH3. Photoelectrochemical modification of Pc-coated microcircuits was carried out in order to obtain submonolayer coverages of a variety of different metals (Ag, Au, Cu, Pt, and Hg) on the Pc film. This modification apparently provides new chemisorption sites for NH3, thus improving the performance of these microcircuit assemblies as NH3 sensors In N2 and In air. The Hg-modlfied microcircuits demonstrated a superior performance compared to the microcircuits modified with other metals, by showing a linear photocurrent response as a function of NH3 concentration In N2 at room temperature over the range from ca. 1.5 to 5.4 ppm, and a logarithmic relationship above that level (up to ca. 84 ppm). Photoconductivity measurements in NH3-air mixtures were carried out on microcircuit assemblies "as-prepared" and after photoelectrochemical modification. The presence of the metal modifier on the InPc-CI film markedly Improves the assembly performance In air, providing a detection limit for NH3 in air of ca. 1.0 part per thousand (ppt). The effect on the photoconductivity of 02 and other impurities present in GaPc-CI and InPc-CI Is discussed, and a mechanism Is proposed to explain the variations observed In the photocurrent response to NH3 in these assemblies before and after modification.

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