What Is Radioanalytical Chemistry?

The subject of microanalysis by measuring radioactive or nuclear phenomena, also known as nuclear analytical chemistry.

Chinese name: Radioanalytical chemistry
Measure: By measuring radioactive or nuclear phenomena

nickname: Nuclear Analytical Chemistry
Time: Early 20th Century

A brief history of radioanalytical chemistry

At the beginning of the 20th century, with the discovery of natural radioactivity, the use of natural radionuclides in analytical chemistry was explored to simplify operations and increase the sensitivity of analysis. In 1912, G. Hevesi and others first used radioactive lead (210Pb) as an indicator to determine the solubility of lead chromate. In 1925, R. Ellenberg used radioactive lead (212Pb) as an indicator to analyze natural lead. In 1932, in order to determine the trace lead in granite, Hevisi et al. Added radioactive lead of known specific activity to the sample solution before analyzing the sample, and performed a lead analysis using the isotope dilution method to obtain satisfactory results. All of these provide conditions for the application of radioactive indicators in analytical chemistry. It has also been widely used in analysis operations such as extraction, precipitation, adsorption, titration and evaporation. In 1934, F. Joliot-Curie and I. Joliot-Curie discovered artificial radioactivity, and E. Fermi and others proposed that almost all elements can induce radioactivity under the action of thermal neutrons. In 1936, Hevisi and H. Levy used the (n, ) nuclear reaction for the first time to successfully analyze the impurities such as ytterbium in yttrium oxide and ytterbium in ytterbium oxide, opening up a new field of activation analysis. Subsequently, in 1938, GT Sieborg et al. Performed the activation analysis of charged particles for the first time. With the establishment of reactors and various accelerators, the continuous improvement of multi-channel spectrometers and the popularization and application of microprocessors, activation analysis has achieved rapid development. Since the 1950s, microanalysis technology (ie, nuclear analysis technology) using nuclear phenomena has been gradually developed and improved. Among them are the application of positron annihilation technology to study the microstructure of matter through the interaction of positrons and matter, the application of -ray resonance absorption of nucleus without recoil-the Mossbauer effect-as well as ion beam backscatter analysis and nuclear reactions Analysis, application of channel effects and particle-excited X-ray fluorescence analysis developed in the 1970s. Radioanalytical chemistry has been valued and developed rapidly due to its advantages such as high sensitivity, small sampling volume, and no damage to samples.

Radioanalytical chemistry

The commonly used methods in radioanalytical chemistry are divided into two categories: methods of radioisotopes as indicators, such as radioanalysis, radiochemical analysis, isotope dilution, etc .; choose the appropriate type and energy of incident particles to bombard the sample and detect Methods for the properties and intensity of various characteristic radiations emitted, such as activation analysis, particle-excited X-ray fluorescence analysis, Mossbauer spectroscopy, nuclear magnetic resonance spectroscopy, positron annihilation, and synchrotron radiation.

Radiochemical analysis

An analytical method that uses radionuclides and radiolabeled compounds as indicators and determines the content of non-radioactive samples to be measured by measuring their radioactivity. The radiometric method used in volume analysis is called radiometric titration.

Radiochemical analysis

A technique to determine the amount of radioactive material contained in a sample by measuring the radioactivity after the sample is separated and purified by an appropriate method. For example, by determining the radioactivity of the natural radionuclide potassium 40 (half-life of 1.28 × 109 years and abundance of 0.111%), the method for determining the potassium content is obtained. The isotope dilution method mixes a known radioactive isotope or labeled compound of the known specific activity with the sample, homogeneously mixes it with a sample, separates and purifies a part of it, and measures its specific activity. Calculate the content of the analyte based on the change in specific activity before and after mixing, that is, the isotope dilution factor. (See isotope dilution method, substoichiometric analysis)

Radioactive chemical activation analysis

After the stable nuclide in the test sample is converted to a radionuclide by a nuclear reaction, the content of the test object is determined by the nuclear reaction cross section, the particle fluence rate, the ray energy, the half-life, and the radioactivity. Can be divided into neutron activation analysis, charged particle activation analysis and photon activation analysis. As a high-sensitivity nuclear analysis technology, activation analysis is widely used in the analysis of biological samples and trace materials in high-purity materials, and in the fields of environmental science, archeology, and forensic science. The analytical sensitivity is 10-8 to 10-11 grams. Excited X-ray fluorescence analysis When , , or X-rays are applied to a sample, orbital electrons absorb part of their kinetic energy due to Coulomb scattering, leaving the atom in an excited state. Characteristic X-rays are emitted when the excited state returns to the ground state, and the type and content of the elements are analyzed based on the energy and intensity of this characteristic X-ray. Its sensitivity is very high and it is widely used. (See X-ray fluorescence spectrometry)

µX Radioanalytical Chemistry & micro; X-ray Fluorescence Analysis

When a negatively charged & micro; submicron with a certain energy is injected into the sample to be measured, it is trapped to form a & micro; subatomic atom due to the coulomb's gravitational force, and a series of characteristic X-rays, namely ; -X-rays, which can analyze the chemical composition and state of the sample. (See & micro; X-ray analysis)

Radio Analytical Chemistry Mossbauer Resonance Spectrum

That is, the nuclear -ray resonance spectrum without recoil. Due to its very high resolving power, even small changes in the state of electrons outside the nucleus can be measured, so information such as chemical shifts, intramolecular binding states, and intermolecular interactions can be obtained. It has been used in the analysis of physical and chemical states of iron, tin, hafnium, hafnium, tantalum, etc. (See Mossbauer spectroscopy)

Radioanalytical positron annihilation

A positron is an antiparticle of an electron. This method uses the annihilation lifetime of positrons to study the microstructure of matter, such as metal defects and phase transitions of various materials, and to study free electrons and solvated electrons in solutions.

Radioanalytical chemical nuclear magnetic resonance

NMR spectral characteristics such as chemical migration, coupling constants, multiplicity, width and intensity of absorption peaks, and temperature effects are used to determine the molecular structure of a sample, especially the molecular structure of organic compounds.

Radioanalytical chemical characteristics

Compared with general analytical chemistry, radioanalytical chemistry has the following characteristics: based on the measurement of radioactive or characteristic radiation, high analytical sensitivity (generally up to 1ppm), high accuracy, fast analysis speed, simple and reliable method, small sampling volume, and sometimes can Destroy the sample structure, etc.

Each analysis method has its own characteristics and optimal analysis range. Isotope dilution requires a radioactivity standard with known specific activity, which is not required for substoichiometry; neutron activation analysis is generally more suitable for heavy and moderate light element analysis, and can analyze thick samples; charged particle activation analysis and back analysis Scattering analysis is mainly used for surface analysis, of which charged particle activation analysis is particularly suitable for light element analysis, backscatter analysis is more sensitive to medium and heavy elements, and X-ray fluorescence analysis has better resolution and detection sensitivity. Generally, the appropriate analysis method is selected according to the sample conditions and analysis requirements. None of the analytical methods are comprehensive and appropriate, and sometimes a combination of methods is required to obtain satisfactory results.