Valve Chemical Composition Analysis
1) Chemical analysis
Chemical analysis is a quantitative test that is based on the chemical reactions of substances and has a long history at the base of which analytical chemistry is found, also known as classical analysis. Based on the amount of the sample, the amount of reaction products or the amount of reagents consumed and the stoichiometric relationship of the reaction, the amount of the component to be tested is calculated. Another important analytical method of instrumental analysis is relative quantification, which is estimated on the basis of the standard working curve. Chemical analysis can be divided into titration analysis and gravimetric analysis according to its operating method. In recent years another concept of analysis has formed in China, called “microspectral analysis” technology which includes: principal component analysis and full component analysis and so on.
Based on the concentration and volume of the standard solution consumed by the titration and the quantitative relationship of the chemical reaction between the measured substance and the standard solution, the content of the measured substance is obtained. This analysis is called titration or volumetric and uses four main solution equilibria: acid-base balance (ionization), redox balance, complexation balance (coordination), and precipitation-dissolution balance.
The titration analysis can be divided into:
Acid-base titration method: measure the pH and the content of various acids and bases
Redox titration method: to measure substances with redox properties
Complexometric titration: measure the content of metal ions
Precipitation titration: measuring halogen and silver
Based on the chemical properties of the substance, select a suitable chemical reaction to convert the measured component into a form of precipitate or gas with a fixed composition. With this analysis, a series of treatments are carried out such as: passivation, drying, combustion or absorption by absorbents and
accurate weighing to know the content of the measured components.
2) Spectral analyzes
This method identifies and determines its chemical composition and relative content in a substance, based on its spectrum. Its advantages are sensitivity and speed.
Spectral analysis can be divided into 2 types:
Emission spectral analysis
Absorption spectral analysis
Spectroscopic analysis of the measured components is called atomic spectroscopy, the measured components are molecules called molecular spectroscopy.
The analysis of the emission spectrum consists in calculating the content based on the intensity of the characteristic spectrum emitted by the atom or molecule tested in the excited state. The absorption spectrum is based on the characteristic spectrum of the element to be measured and the content of the
element is calculated from the weakened intensity after the ground state atom of the element to be measured in the sample vapor has absorbed the spectrum of the measured element .
It complies with the Ramper-Beer law:
A = -lg I / I o = -lgT = KCL
*Where I is the intensity of the transmitted light, I0 is the intensity of the light emitted, T is the transmittance and L is
the path optical light passing through the atomizer. L is a constant value therefore A = KC.
The atom of any element is composed of a nucleus and electrons that move around the nucleus. The electrons outside the nucleus are distributed in layers based on their energy levels to form different energy levels. Therefore, an atomic nucleus can have multiple energy levels.
The state of the energy level with the lowest energy is called the energy level of the ground state (E0 = 0), the remaining energy levels are called the energy levels of the excited state, and the excited state with the lowest energy is called first excited state. Normally, the atom is in the ground state and the electrons outside the nucleus move in their orbits with the lowest energy. If some external energy such as light energy is supplied to the ground state atom, when the external light energy E is exactly equal to the difference in energy level E between the ground state and some higher energy
level in the atom of the ground state, the atom will absorb the light of this characteristic wavelength, the external electrons pass from the ground state to the corresponding excited state. Some characteristic spectral lines are missing from the spectral lines of light that originally provided the energy, resulting in
atomic absorption spectra. After the electron has passed to a higher energy level, it is in an excited state, but the electron in the excited state is unstable. After about 10-8 seconds, the excited state electron will return to the ground state or other lower energy levels and the energy absorbed by the electronic transition will be changed. It is released in the form of light, a process called atomic emission spectroscopy. Visible atomic absorption spectroscopy processes absorb radiant energy, while atomic emission spectroscopy processes release radiant energy.
3) Mass spectrometry analysis
This method of qualitative, quantitative and structural analysis uses mass spectrometry is called mass spectrometry (spectrum formed by the order of the mass-charge ratio of ions, i.e. mass-charge ratio).
Principle: Mass spectrometry uses high-speed electrons to collide with molecules or gas atoms, and ionized positive ions are accelerated in the mass analyzer, then Collect and record in order of mass-to-charge ratio (m / z) to get the mass spectrum. A mass spectrum is not a spectrum, but a mass spectrum of matter-charged particles.
The basic procedure is:
vacuum system → sample injection system → ion source → mass analyzer → detector → recording system
4) Chromatographic analysis
Chromatography is a separation and analysis method widely used in analytical chemistry, organic chemistry, biochemistry and other fields. It uses the selective distribution of different substances in different phases and elutes the mixture in the mobile phase compared to the stationary phase. Different substances in the mixture will move along the stationary phase at different rates and eventually achieve the separation effect.