RNAA

Of the four strategies given above, the best condition for obtaining independent data for quality control (QC) are satisfied when INAA and RNAA results are compared, because the use of RNAA dramatically improves the selectivity of signal measurement and eliminates or greafiy reduces the measurement uncertainty sotuces, such as spectral interferences. A variety of radiochemical separations and... 

As an example of the capabilities of a combination of INAA and RNAA using a two group separation scheme for the simultaneous determination of As, Cd, Cu, Mo, Sb, Hg, and Se (Kucera and Soukal 1993), and a single separation procedure for vanadium determination (Byrne and Kucera 1991), Table 3.8 shows results for NIST-SRM-i573a Tomato Leaves that were obtained prior to certification of this material (Kucera 1995), and later on taken into consideration for deriving the NIST certified and information values (Becker 1995, personal communication). 

Tab. 3.8 INAA and RNAA results for NIST SRM-i573a Tomato Leaves (dry weight) (Kucera 1995)...

Rapid RNAA for iodine in urine by different separation techniques. Analyst 117 251-258. 

Kucera J, Vobecky M, Soukal L, Zakoucky D, and Venos D (1997) Low level determination of thallium in biological and environmental reference materials by RNAA using several counting methods. J Radioanal Nud Chem 217 131-137. 

During the late 1960s and early 1970s, neutron activation analysis provided a new way to measure bulk chemical composition. Neutron activation analysis utilizes (n,y) reactions to identify elements. A sample is placed in a nuclear reactor where thermal neutrons are captured by atoms in the sample and become radioactive. When they decay, the radioactive isotopes emit characteristic y-rays that are measured to determine abundances. Approximately 35 elements are routinely measured by neutron activation analysis. A number of others produce radioactive isotopes that emit y-rays, but their half-lives are too short to be useful. Unfortunately, silicon is one of these elements. Other elements do not produce y-ray-emitting isotopes when irradiated with neutrons. There are two methods of using neutron activation to determine bulk compositions, instrumental neutron activation analysis (INAA) and radiochemical neutron activation analysis (RNAA). 

In RNAA, the sample is irradiated as for INAA. But after irradiation, the sample is chemically processed to separate elements with y-rays whose energies cannot be resolved by the detectors and to concentrate the element of interest to improve sensitivity. Typically RNAA involves larger samples in order to facilitate chemical processing. 

Definitive methods (i.e., ratio primary reference measurement procedures, RPRMPs) based on radiochemical NAA (RNAA) were elaborated for several elements [46-48]. As methods of the highest metrological quality, they served as a tool for independent verification of reliability of the certified values. In all cases where these methods could be used, there was very good agreement between the certified values established by the procedure described above and the results obtained by RPRMPs. Certified values are presented in the form ... 

Dyhczynski, R.S., Danko, B., Polkowska-Motrenko, H., Samczynski, Z. RNAA in metrology a highly accurate (definitive) method. Talanta 71, 529-536 (2007)... 

Chajduk, E., Polkowska-Motrenko, H., Dybczynski, R.S. A definitive RNAA method for selenium determination in biological samples. Uncertainty evaluation and assessment of degree of accuracy. Accred. Qual. Assur. 13, 443 51 (2008)... 

Kucera et al. [161] performed a comparative analysis of three procedures for determining I in food. Their accuracy and precision were checked against reference materials based on food products. The limit of detection was 1 pg/kg. Instrumental NAA (INAA) and replicate sample INAA (RSINAA) were used in Portugal to test a wide assortment of food products for their total Se content [162], INAA and radiochemical NAA (RNAA) were also used to assess the quality of bottled water sold in Greece [163]. Elements such as U, Ba, La, Sb, Ca, Cr, Zn, K, As, Br, Se and... 

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