Simultaneous Determination of Multiple Actinide Elements in a Variety of Soils Utilizing a Standardized Sequential Extraction Protocol

To obtain a better understanding of the mobility of actinide element contaminants in the environment, the association of the contaminants with specific host phases of soils and sediments must be investigated. This investigation is most commonly conducted using sequential extraction techniques that employ the selective dissolution of soil phases with increasingly aggressive chemical treatment. Though several sequential extraction studies exist in literature, conclusions cannot be made by direct comparison of data due to the lack of uniformity in the protocols used. This work aims to continue development of a standard sequential extraction protocol and expanding its capabilities to include the analysis of multiple actinide elements across a broad range of soil types. A five-step sequential extraction procedure was used to analyze extraction behaviors of 232Th, 238U, 239,240Pu and 241Am from four standard reference materials chosen to represent a broad range of geochemical soil types. Radioanalytical separations were performed using an extraction chromatography based separation procedure prior to CeF3 microprecipitation sample mounting and counting by alpha spectroscopy. Stable element analysis of aluminum, iron, manganese, and strontium was performed by inductively coupled plasma - mass spectrometry to monitor phase selectivity and model potential fission product mobility. An investigation of complete dissolution techniques for a potential sixth fraction was conducted for the application to soils with high concentrations of insoluble metals. Results show variations in leaching behaviors potentially caused by the geochemical host phase of the soil, chemical form of the extracted elements, and environmental weathering conditions

Investigations on plasma cholinesterase in man and animals using succinylcholine as the substrate

A simple, precise "reaction rate" assay for plasma cholinesterase based on a succiny1choline substrate has been developed. It's ability to define individuals at risk of succiny1choline sensitivity and identify those who had experienced apnoea was superior to the previously best available assay. However it was not able to identify abnormal forms of cholinesterase which could hydrolyze conventional assay substrates but not succinylcholine. It was-concluded that if these forms exist their numbers are small. The failure to identify such cholinesterase types may have been because'the substrate concentration chosen for the assay was higher than that found"pharnacologically. However investigation of the kinetics of the succiny1choline-cholinesterase interaction showed that this was not the case. The assay was applied to the assessment of liver dysfunction and compared to three established methods was superior. All assays identified patients with severe liver disease but the succinylcholine-based one identified more patients with moderate/mild disease. The assay was also used to investigate the clinical observation that children require a higher dose of succiny1choline for muscle relaxation than adults. Infants were found to have higher succiny1choline activities than adults which is compatible with their relative resistance to the drug. Finally cholinesterase measurements were made, using a range of substrates including succinylcholine, in a variety of animal species. Results show that only when succiny1choline is used as the substrate for'the assay of cholinesterase does enzyme activity correlate with tolerance to it's muscle relaxant properties. The choice of procedure for the analysis of any biochemical variable depends on a number of criteria including ease of assay, precision, accuracy and cost; however the primary consideration should be the ability of the method to provide clinically useful information. Based on all these criteria, in particular the latter, succiny1choline must be considered as the substrate of choice