Molecular neutron activation analysis

Bennett BG (1983) Exposure of man to environmental selenium - an exposure commitment assessment. Sci Total Environ 31 17—127. Blotcky AJ, Hansen GT, Opeianio-Buengamino LR and Rack EP (1985) Determination oftrime-thylselenonium ion in urine by ion-exchange chromatography and molecular neutron activation analysis. Anal Chem 57 937-941. 

The chemical speciation study of trace elements in life sciences has been paid more and more attention in recent years, mainly because it can provide more significant information on the pathway, distribution, accumulation, excretion, and functions of trace elements in biological systems of interest than the traditional bulk composition study. Almost all speciation techniques consist of two steps. The first step involves the separation of species from the sample followed by the second step of element specific detection. The so-called molecular neutron activation analysis (MoNAA) or speciation neutron activation analysis (SNAA) is, in fact, a combination of conventional NAA with physical, chemical, or biological separation procedures in order to meet the ever-increasing need for chemical species study. 

In 1980s, Rack and colleagues at University of Nebraska carried out a series study on speciation of iodine, chlorinated pesticides, and seleium in urine using liquid chromatography and molecular neutron activation analysis. They developed procedures for trace level determination of iodoamino acids and... 

It is seen by examination of Table 1.11(b) that a wide variety of techniques have been employed including spectrophotometry (four determinants), combustion and wet digestion methods and inductively coupled plasma atomic emission spectrometry (three determinants each), atomic absorption spectrometry, potentiometric methods, molecular absorption spectrometry and gas chromatography (two determinants each), and flow-injection analysis and neutron activation analysis (one determinant each). Between them these techniques are capable of determining boron, halogens, total and particulate carbon, nitrogen, phosphorus, sulphur, silicon, selenium, arsenic antimony and bismuth in soils. 

Other frequently used methods for determining fluoride include ion and gas chromatography [150,204,205] and aluminium monofluoride (AIF) molecular absorption spectrometry [206,207]. Less frequently employed methods include enzymatic [208], catalytic [209], polarographic [210] and voltammetric methods [211], helium microwave-induced [212] or inductively coupled plasma atomic emission spectrometry [213], electrothermal atomic absorption spectrometry [214], inductively coupled plasma-mass spectrometry [215], radioactivation [216], proton-induced gamma emission [217], near-infrared spectroscopy [218] and neutron activation analysis [219]. 

Tn the early 1950s, when Taylor and Datz (I) were planning their pioneering crossed molecular beam reactive scattering experiments, they planned to use neutron activation analysis to measure the angular distribution of condensed product KBr molecules formed in Reaction 1... 

Melting point Mass spectrometry Multiplicative signal correction Microspecular reflectance Molecular weight Neutron activation analysis Nickel oxide... 

Neutron activation analysis (NAA) also was used to verify the presence of both silicon and oxygen in the polymer and to calculate functional molecular weights. Functional molecular weights were obtained by comparing the percent silicon or oxygen to the percent carbon. These values agree within 5% of the values determined by NMR spectroscopy. 

The methods used can be conveniently arranged into a number of categories (a) fractionation by precipitation (b) fractionation by distillation (c) separation by chromatographic techniques (d) chemical analysis by spectrophotometric techniques (infrared, ultraviolet, nuclear magnetic resource. X-ray fluorescence, emission, neutron activation), titrimetric and gravimetric techniques, and elemental analysis and (e) molecular weight analysis by mass spectrometry, vapor pressure osmometry, and size exclusion chromatography. 

The principal use of the neutron activation technique is for trace element analysis. Conventional methods entail a loss of the molecular identity of the original atoms, so that they are not suitable for the identification of compounds containing such atoms. However, by subjecting the sample to a separation procedure such as paper chromatography prior to activation, the identification of molecular species becomes possible. 

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