Automation radiochemical analysis

Both radiometric and mass spectrometric detection approaches have been used in automated radiochemical analysis, depending on the radionuclides of interest and the capabilities of the laboratory involved. The tradeoffs between radiation counting and atom counting have been described.14 16 17 Short-lived fission products may be advantageously detected with radiation detection, whereas long-lived (low specific activity) radionuclides can be determined with better sensitivity using ICP-MS. 

The total effective analytical efficiency (product of the recovery efficiency and the detection efficiency) is calculated based on the difference in analytical response obtained by the analysis of the spiked and unspiked samples. This approach provides a reliable method for remote, matrix matched, instrument calibration. Automated standard addition can be used for each sample or batch of samples. The automated radiochemical analysis procedure is rapid, with a total analysis time of 12.5 min per sample. The total analysis time for the standard addition measurement is 22 min (including analysis of both unspiked and spiked samples). For low-level samples, a much longer counting time can be expected. 

Combination of ciassicai radiochemicai methods with fiow analysis techniques to automate radiochemical analysis. (For color version of this figure, the reader is referred to the online version of this book.)... 

Q Automation of Extraction Chromatographic and Ion Exchange Separations for Radiochemical Analysis and Monitoring... 

Laboratory robotics represents an attractive approach for the automation of sample preparation and separation steps in radiochemical analysis, and for many years, such methods have been routinely used by laboratories serving the analytical needs of the International Atomic Energy Association.64 68-72 However, there are currently a limited number of published studies containing technical details on the radiochemical separations and how they were automated. Accordingly, the remainder of this chapter will focus on fluidic approaches. 

By the late 1990s and into the 2000s, a number of additional groups became involved in automated fluidic separations for radiochemical analysis, especially as a front end for ICP-MS. Published journal articles on fluidic separations for radio-metric or mass spectrometric detection are summarized in Tables 9.1 through 9.5. The majority of such studies have used extraction chromatographic separations, and these will be the main focus of the remainder of this chapter. Section 9.4 describes methods that combine separation and detection. Section 9.5 describes a fully automated system that combines sample preparation, separation, and detection. 

Conventional radiochemical analysis of nuclear process or waste samples in the laboratory entails three primary activities sample preparation, radiochemical separation, and detection. Each of these activities may entail multiple steps. The automated fluidic methods described above, typically also carried out in the laboratory, link separation and detection. Sample preparation has, in many cases, been carried out first by manual laboratory methods. 

Grate, J. W. and Egorov, O. B., Automated radiochemical separation, analysis, and sensing, in Handbook of Radioactivity Analysis, 2nd ed., L Annunziata, M. F., Ed., Elsevier, Academic Press San Diego, 2003,1129-1164. 

Egorov, O., Grate, J. W., and Ruzicka, J., Automation of radiochemical analysis by flow injection techniques Am-Pu separation using TRU-resin sorbent extraction column, J. Radioanal. Nucl. Chem., 234, 231-235, 1998. 

Lievens P, Versieck J, Cornells R, et al. 1977. The distribution of trace elements in normal human liver determined by semi-automated radiochemical neutron activation analysis. J Radioanal Chem 37 483-496. 

The second step of the analytical process — the components analysis or black box — can be automated by using automatic devices. The samples automatically change the automation required for this step, decreasing the time needed for the analytical process. This has been used in radiochemical analysis for operator protection. Now, automatic devices are often used for RXF, AAS, and ESCA methods, as well as for chromatographic techniques, such as HPLC, to increase the speed of the analytical process. By using automatic titration, the reliability and quality of the analytical information increases, the objectivity increases and the time needed decreases dramatically. 

Egorov, O. B., O Hara, M. J., Addleman, S. R., Grate, J. W. 2003. Automation of radiochemical analysis from groundwater monitoring to nuclear waste analysis in Radioanalytical Methods in Interdisciplinary Research Fundamental to Cutting Edge Applications. ASC Symposium Series 868. Washington, DC ACS. 

Most of the effluent and environmental radioactivity measurements are made using gamma-ray spectrometry. This is a far more cost effective approach than radiochemical analysis the Instrumental measurement can be readily automated, and detection decisions can be made more or less simultaneously for many radionuclides. The validity of those decisions, and of the corresponding detection limits, however, requires either that the peaks be Isolated and lie on a linear baseline, or that a detection limit model be employed which Is more complex than that used for "simple" counting. Baseline or interference model uncertainties should be Included, and an iterative solution is required to estimate the detection limit when spectrum deconvolution is involved. Details are beyond the scope of this chapter, but a relatively simple limiting estimate can be derived by treating the estimated standard error for a low level radionuclide peak of interest as though it were the null standard error, [12, p. 81]. 

Activation analysis is the other field of radiochemical analysis that has become of major importance, particularly neutron activation analysis. In this method nuclear transformations are carried out by irradiation with neutrons. The nature and the intensity of the radiation emitted by the radionuclides formed are characteristic, respectively, of the nature and concentrations of the atoms irradiated. Activation analysis is one of the most sensitive methods, an important tool for the analysis of high-purity materials, and lends itself to automation. The technique was devised by Hevesy, who with Levi in 1936 determined dysprosium in yttrium by measuring the radiation of dysprosium after irradiation with neutrons from a Po-Be neutron source. At the time the nature of the radiation was characterized by half-life, and the only available neutron sources were Po-Be and Ra-Be, which were of low efficiency. Hevesy s paper was not followed up for many years. The importance of activation analysis increased dramatically after the emergence of accelerators and reactors in which almost all elements could be activated. Hevesy received the 1943 Nobel prize in chemistry for work on the use of isotopes as tracers in the study of chemical processes . 

Y. Fajardo, J. Avivar, L. Ferrer, E. Gomez, M. Casas, V. Cerda, Automation of radiochemical analysis hy applying flow techniques to enviromnental samples. Trends Anal. Chem. 29 (2010) 1399—1408. 

In conclusion, the best interface and a good correlation of parameters of both the apparatus and the technique will assure the best reliability for analytical information. Automation of the apparatus not only improves the objectivity of the analysis, but is also necessary for the operator s protection. When radiochemical methods are used with automation, it is possible to obtain objective and reliable analytical information that is independent of the ambient conditions. For environmental analysis, automatic spectrometers are important to obtain continuous reliable analytical information, which is called environment monitorization. In cosmochemistry, automation of equipment and robotics is essential to assure the reliability of the information that is received by teleanalysis.218... 

Although Meinke (603) points out that automation in analytical chemistry is most desirable to remove the drawbacks of radiochemical separations in activation analysis, many other analysts who use activation analysis for trace element determinations in biological materials continue effective research on separation systems for a single element or a small group of elements with similar chemical characteristics for example, the methods and techniques in the publication by Gorsuch (338) have been used by many analysts in their activation analysis determinations of trace elements. Other successful microchemical techniques used in activation analysis have been described by Pijck and Hoste (713), Sion, Hoste, and Gillis (858), Girardi and Merlini (331), and Smales and Mapper (864). 

---