Oleg B. Egorov

Automated Radiochemical Separation, Analysis, and Sensing

Destructive analysis, complete with radiochemical separation of the radionuclide(s) of interest from the sample matrix and potential interferences, is a fundamental and often critical component of radioanalytical measurements. Faster automated methods for radiochemical separation and analysis are needed to support radioanalytical laboratories. In addition, automation is required to move destructive analysis methods from the laboratory to on-line monitoring applications at nuclear facilities, and to sense radionuclides in the environment, at-site or in situ . Automation offers many significant advantages, including more consistent analytical protocols, increased reliability, improved safety, and reduced worker exposure to radioactivity, as well as shorter analysis times, higher throughput, and lower costs. In addition, automation can enable measurements that are not currently considered feasible, because they are too costly and time consuming for manual laboratory analysis, or too difficult to deploy on-line or at-site. Currently, radiochemical automation is either practiced or under development in the following areas: analysis of spent fuel to support nuclear safeguards, analysis of environmental samples related to management of nuclear sites, bioassay samples, automated monitoring for industrial-scale nuclear processes, sensing systems for radionuclides in environmental water samples, heavy element research, and medical isotope generation. This chapter presents principles and selected applications of automation in radiochemical separations, analysis, monitoring, and sensing, with comprehensive citations to the literature.

Direct spectrophotometric analysis of Cr(VI) using a liquid waveguide capillary cell.

Hexavalent chromium Cr(VI) is a notorious ground water contaminant toxic to humans and animals. Assessment of an exposure risk for aquatic receptors necessitates frequent Cr(VI) concentration data from a range of surface and groundwater locations at Cr(VI) contamination sites. In this work, we demonstrate that enhanced ultraviolet–visible (UV-vis) spectroscopy using a liquid waveguide capillary cell (LWCC) offers an easy-to-use and economical methodology for the determination of chromate anion CrO42− in Hanford natural waters without chemical pretreatment and generation of hazardous waste. Direct determination of CrO42− in actual surface and ground water samples with the complexities of competing ions, dissolved organics, and other potential interfering agents was achieved by measuring the chromate optical absorbance at 372 nm. For a 100 cm path length LWCC, the detection limit for chromate was found to be as low as 0.073 ppb. A quantitative relationship between the intensity of the absorbance signal and water pH allowed for the straightforward calculation of total Cr(VI) content in natural water. The described method is applicable for in-field monitoring of Cr(VI) in environmental water samples at trace levels.

14 – AUTOMATED RADIOCHEMICAL SEPARATION, ANALYSIS, AND SENSING

Automation in radiochemical analysis offers many significant advantages, including reduced worker exposure to radioactivity, increased reliability, improved safety, and more consistent analytical protocols. Automation is particularly important in addressing the requirements for carrying out radiochemical separations prior to detecting or quantifying the radionuclides of interest. These aspects of radiochemical analysis can be particularly time consuming and costly. Classical sample preparation methods in radiochemistry entail tedious manual separations such as precipitations and extractions. Modern radiochemical separations carried out on solid phase separation materials have considerable advantages, and are suitable for automation.

Sequential injection separation and sensing

Automated microfluidic analysis has historically been carried out by flow injection analysis techniques. Sequential injection analysis represents a more versatile method for automated fluid handling. We have explored the use of sequential injection analysis for performing microcolumn separations. These separations can be used as part of a microanalytical procedure, or for sample preparation. In addition, with detection of retained species on the microcolumn, sequential injection separation represents a technique for sensing. Recently, it has been demonstrated that sequential injection separation can be carried out with renewable separation columns--the beads with interactive surfaces can be delivered to the microcolumn, used for processing the sample, and discarded after each measurement. Delivery of new beads for each measurement provides a method for renewable surface separation and renewable surface sensing. Applications in environmental analysis and bioanalytical chemistry will be presented.