Activation spectrometry

D.J. Winefordner and I.M. Kolthoff (eds), Activation Spectrometry in Chemical Analysis, Wiley-Interscience, New York, NY (1991). 

Neutron Activation Spectrometry. Another instrumental technique which has applicability to a wide range of elements is neutron activation analysis. In this method the sample (which could be orange juice without any prior sample treatment) is irradiated with a strong neutron flux. The elements of analytical interest are thus converted to unstable isotopes which decay with characteristic energies and thus measurement of the intensities results in analytical values for the elements of interest. There are some serious drawbacks to this method, however. The matrix can cause severe background effects especially when the sample contains large amounts of an element, like potassium, which is the situation with orange juice. In this event tedious chemical separations must be carried out to achieve adequate selectivity, accuracy... 

Vol. 117. Applications of Fluorescence in Immunoassays. By Ilkka Hemmila Vol. 118. Principles and Practice of Spectroscopic Calibration. By Howard Mark Vol. 119. Activation Spectrometry in Chemical Analysis. By S. J. Parry Vol. 120. Remote Sensing by Fourier IVansform Spectrometry. By Reinhard Beer Vol. 121. Detectors for Capillary Chromatography. Edited by Herbert H. Hill and Dennis McMinn... 

Figure 5 The efficiency curves for a coaxial p-type, a coaxial n-type, and a planar germanium detector. (Reprinted with permission from Parry SJ (1991) Activation spectrometry in chemical analysis.)...

Parry JS (1991) Activation Spectrometry in Chemical Analysis. New York Wiley. 

Elements that cannot be found by straightforward activation spectrometry (INAA) because of other dominant or interfering activity may be determined by radiochemical neutron activation analysis (RNAA). 

In vivo analysis of the human body by means of activation spectrometry requires irradiation with energetic neutrons in order to reduce excessive absorption in the outer layers by thermal neutron capture. At the same time the radiation dose must be as low as possible with an upper limit of the order of 10 mSv under these circumstances it is found that better results for the major elements are found [7] when y-spectrometry is carried out both during and immediately after irradiation, so that the irradiation emitted directly as a result of the nuclear reaction is measured. 

This method of activation spectrometry is often referred to as prompt y neutron activation analysis (PGNAA) and may take advantage of the fact that the slowing down of energetic neutrons in the human body takes time. 

TABLE 2. In Vivo Determination of Major and Minor Elements by Neutron Activation Spectrometry... 

The use of high-resolution Ge(Li) gamma-ray detectors allows limited nondestructive multielement analysis, but when the number of elements determined is large (> 10) precision and accuracy for many of the elements may be expected to suffer (> + 20 %). This nondestructive approach, i.e., activation spectrometry, usually requires two or more separate irradiations with corresponding decay periods prior... 

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