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Selenium is an essential nutrient of fundamental importance to human biology. It is an essential  constituent of more than two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage and infection [1]. Thus the determination of selenium at trace and ultra-trace levels has become of increasing importance in life sciences [2–5]. The 82Se/76Se   ratio remains relatively constant for ores, but in plants and soil varies from -1.2% to +0.2% [6]. The variations of 82Se/76Se ratio in plant material are believed to be a result of different in the bacteria residing in the plants. 
The concentration of trace elements nutritive importance and toxic effects in biological materials can be determined using different analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), and RNAA [7, 8]. Unfortunately, they require a series of subsequent dissolution and chemical separation and thus have the inherent possibility of losing analytes or altering the contamination level. 

PAA has been established for more than fifty years [9, 10], and became more commonly used by the 1980s, when high intensity photon sources became available [11].  Sample preparation for PAA is simple and for most of the samples chemical separation is not necessary. As a result, PAA developed into a relatively common tool for a variety of analytical problems, particularly where high sensitivity is required. Photon activation analysis of selenium has been done in the past using either 75Se or 81,81mSe radioisotopes. 75Se has a relatively long half-life of ~119 days, and requires long irradiation and long cooling time [12, 13]. Both 81Se and 81mSe are rather short-lived (T1/2 < 1 hour) and have also been used in PAA [14, 15]. The goal of this paper is to demonstrate that PAA can be an accurate tool to measure selenium concentration and the 82Se/76Se ratio in soil samples and find its detection limit.

References

1. 	Sunde RA (2012) Modern Nutrition in Health and Disease. Lippinkott Williams & Wilkins
2. 	Chajduk E, Polkowska-Motrenko H, Dybczyński RS (2008) A definitive RNAA method for determination of selenium in biological samples: uncertainty evaluation and assessment of degree of accuracy. Accredit Qual Assur 13:443–451. doi: 10.1007/s00769-008-0377-7
3. 	Bakir MA, Yaseen T, Sarheel A, Othman I (2004) The determination of selenium concentration in blood and tumour tissues of breast cancer patients in Syria using instrumental neutron activation analysis. J Radioanal Nucl Chem 260:607–612. doi: 10.1023/B:JRNC.0000028220.00481.8e
4. 	Stosnach H (2010) Analytical determination of selenium in medical samples, staple food and dietary supplements by means of total reflection X-ray fluorescence spectroscopy. Spectrochim Acta Part B At Spectrosc 65:859–863. doi: 10.1016/J.SAB.2010.07.001
5. 	Messaoudi M, Begaa S, Hamidatou L, Salhi M (2017) Determination of selenium in roasted beans coffee samples consumed in Algeria by radiochemical neutron activation analysis method. Radiochim Acta. doi: https://doi.org/10.1515/ract-2017-2782
6. 	Krouse HR, Thode HG (1962) THERMODYNAMIC PROPERTIES AND GEOCHEMISTRY OF ISOTOPIC COMPOUNDS OF SELENIUM. Can J Chem 40:367–375. doi: 10.1139/v62-055
7. 	Oleszczuk N, Castro JT, da Silva MM, et al (2007) Method development for the determination of manganese, cobalt and copper in green coffee comparing direct solid sampling electrothermal atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry. Talanta 73:862–869. doi: 10.1016/J.TALANTA.2007.05.005
8. 	Dybczyński RS, Danko B, Polkowska-Motrenko H, Samczyński Z (2007) RNAA in metrology: A highly accurate (definitive) method. Talanta 71:529–536. doi: 10.1016/J.TALANTA.2006.04.021
9. 	Baker CA (1967) Gamma-activation analysis. A review. Analyst 92:601. doi: 10.1039/an9679200601
10. 	Lutz GJ (1971) Photon Activation Analysis -A Review. Anal Chem 43:93–103.
11. 	Starovoitova V, Segebade C (2016) High intensity photon sources for activation analysis. J Radioanal Nucl Chem 1–14. doi: 10.1007/s10967-016-4899-x
12. 	Galatanu V, Engelmann C (1982) Analyse multielementaire des cheveux par photoactivation nucleaire. J Radioanal Chem 74:161–180. doi: 10.1007/BF02520369
13. 	Galatanu V, Engelmann C (1981) Determination de quelques elements traces dans le charbon, d’une maniere non destructive, par photoactivation nucleaire. J Radioanal Chem 67:143–163. doi: 10.1007/BF02516238
14. 	Chattopadhyay A, Jervis RE (1974) Multielement determination in market-garden soils by instrumental photon activation analysis. Anal Chem 46:1630–1639. doi: 10.1021/ac60348a059
15. 	Jervis RE, Tiefenbach B, Chattopadhyay A (1977) Scalp hair as a monitor of population exposure to environmental pollutants. J Radioanal Chem 37:751–760. doi: 10.1007/BF02519387




[[PAA_Selenium#Can_one_perform_PAA_measurements_of_Se-82_and_Se-76.3F]]

[[PAA_Selenium#Can_one_perform_PAA_measurements_of_Se-82_and_Se-76.3F]]