High-performance liquid chromatography system consists of a reservoir, pump, injector, column, detector, recorder and other parts. The mobile phase in the reservoir is pumped into the system by a high-pressure pump, and the sample solution enters the mobile phase through the injector, and is loaded into the column (stationary phase) by the mobile phase. Due to the different distribution coefficients of the components of the sample solution in the two phases, when they move relative to each other in the two phases, after repeated adsorption-desorption distribution process, the components produce a large difference in the speed of movement, and they are separated into individual components in order to flow out from the column, and then pass through the detector. When it passes through the detector, the concentration of the sample is converted into an electrical signal and transmitted to the recorder, and the data is printed out in the form of a graph.
2 Application of high performance liquid chromatography
High-performance liquid chromatography only requires that the sample can be made into a solution, without the limitations of sample volatility, a wide range of mobile phase selection, a wide range of stationary phase, and can therefore separate the thermally unstable and non-volatile, dissociated and non-dissociated, and a variety of molecular weight range of the material.
In conjunction with sample preparation techniques, the high resolution and sensitivity achieved by HPL C makes it possible to separate and simultaneously determine substances with very similar properties, and to separate trace components in complex phases. With the development of stationary phases, it is possible to complete the separation of biochemical substances under conditions that fully maintain their activity.
HPL C has become the most promising method for solving biochemical analytical problems. Because HPL C has the advantages of high resolution, high sensitivity, fast speed, reusable column, and easy to collect the effluent components, it has been widely used in biochemistry, food analysis, pharmaceutical research, environmental analysis, inorganic analysis and other fields. The combination of HPLC and structural instruments is an important development direction.
Liquid chromatography - mass spectrometry technology has been generally valued, such as the analysis of carbamate pesticides and polynuclear aromatic hydrocarbons, etc.; liquid chromatography - infrared spectroscopy linkage is also developing rapidly, such as in the determination of hydrocarbons in water, sea water in the analysis of environmental pollution in the non-volatile hydrocarbons, so that the analysis of environmental pollution has been the development of a new.
The working principle of the spectrophotometer: the substances in solution in the light irradiation excitation, the effect of light absorption, this absorption is selective, a variety of different substances have their own absorption spectra, because of some of the monochromatic light through the solution when the energy will be absorbed and weakened, the degree of light energy weakened and the concentration of the substance has a certain proportionality, that is, in line with the Rambler - Beer's law T = I / I / Beer's law. -Beer's law T = I/I0 LogI0/I = KCL A = KCL where: T transmittance ratio I0 incident intensity I transmitted intensity A absorbance K absorption coefficient L the optical range of the solution C the concentration of the solution is usually done to identify the substance, purity checks, the structure of organic molecules. Spectrophotometer classification: atomic absorption spectrophotometer, fluorescence spectrophotometer, visible spectrophotometer, infrared spectrophotometer, ultraviolet-visible spectrophotometer Different classifications have different applications: atomic absorption spectrophotometer for metallurgy, geology and environmental protection, food, medical, chemical, agriculture and forestry and other industries, materials analysis and quality control departments for constant, trace metal (semi-metallic) elemental analysis of a powerful tool, is the production, education, research and development, and is the first time in the world that a spectrophotometer is used in the field of spectral analysis. It is a powerful tool for the analysis of constant and trace metal (semi-metal) elements in the material analysis and quality control departments of metallurgy, geology, environmental protection, food, medical, chemical, agriculture and forestry industries, and is one of the routine instruments in the analytical laboratories of the production, education and scientific research units. Fluorescence spectrophotometer is a kind of instrument used for scanning the fluorescence spectrum emitted by liquid-phase fluorescent markers. Used in scientific research, chemical industry, medicine, biochemistry, environmental protection, as well as clinical testing, food testing, teaching experiments and other fields. Visible spectrophotometer with transmission ratio, absorbance, concentration of direct determination, with automatic adjustment 0% τ, 100% τ function. It can be equipped with 5cm optical diameter colorimetric frame and 2.3.5cm rectangular cuvette to expand the measurement range. Optional PC software package, through the RS232C connection PC, printer to implement the expansion of functions. Widely used in gold, medicine, food industry, medicine, health, chemical industry, school, biochemistry, petrochemical, quality control, environmental protection and scientific research laboratories and other chemical analysis of infrared spectrophotometer. The general infrared spectrum refers to the mid-infrared spectrum between 2.5-50 microns (corresponding to the wave number 4000-200 cm-1), which is the most commonly used spectral region for the study of organic compounds. Infrared spectroscopy is characterized by its rapidity, small sample size (a few micrograms - a few milligrams), strong characterization (various substances have their own specific infrared spectrograms), the ability to analyze specimens in a variety of states (gas, liquid, and solid), and the ability not to destroy the sample. Infrared spectrometer is chemistry, physics, geology, biology, medicine, textiles, environmental protection and materials science and other important research tools and test means, and far-red spectroscopy is an important means of researching metal coordination compounds. UV-visible spectrophotometer the instrument is simple to operate, perfect function, high reliability, in the domestic leading level. The instrument is easy to operate, perfect function, high reliability, can be widely used in drug testing, drug analysis, environmental testing, health and epidemic prevention food, chemical industry, scientific research and other fields of qualitative and quantitative analysis of substances. It is a necessary instrument for production, scientific research and teaching.
Infrared spectroscopy and the structure of the molecule is closely related to the study of the structure of the molecular characterization of an effective means of comparison with other methods, infrared spectroscopy due to the sample does not have any limitations, it is recognized as an important analytical tool. In the molecular conformation and conformational studies, chemical and chemical, physics, energy, materials, astronomy, meteorology, remote sensing, environment, geology, biology, medicine, drugs, agriculture, food, court identification and industrial process control and other aspects of the analysis of the determination have a very wide range of applications. Infrared spectroscopy can study the structure of molecules and chemical bonds, such as the determination of force constants and molecular symmetry, etc., the use of infrared spectroscopy can determine the bond length and bond angle of molecules, and thus the stereo configuration of molecules. The strength of chemical bonds can be deduced from the force constants obtained, and thermodynamic functions can be calculated from simple positive frequencies. Some groups in the molecule or the chemical bond in different compounds corresponding to the spectral band wave number is basically fixed or only in the small band range changes, so many organic functional groups such as methyl, methylene, carbonyl, cyano, hydroxyl, amine and so on in the infrared spectrum have characteristics of the absorption, through the infrared spectroscopy, people can determine the existence of the unknown samples of which organic functional groups, which is the basis for the final determination of the chemical structure of the unknown substance. This lays the foundation for the final determination of the chemical structure of the unknown substance. Due to intramolecular and intermolecular interactions, the characteristic frequency of organic functional groups will be due to the different chemical environments in which the functional groups are located and the occurrence of subtle changes, which creates the conditions for the study of the characterization of intramolecular and intermolecular interactions. Molecules in the low wavelength region of many simple positive vibration often involves all the atoms in the molecule, different molecules vibrate in a different way from each other, which makes the infrared spectra have a high degree of characterization like fingerprints, known as the fingerprint region. Using this feature, people have collected the infrared spectra of thousands of known compounds, and stored them in the computer, compiled into the infrared spectral standard spectral library. People only need to measure the infrared spectra of unknown substances and the standard spectral library of spectral comparison, you can quickly determine the composition of unknown compounds. Contemporary development of infrared spectroscopy technology has made the significance of infrared spectroscopy far beyond the stage of simple routine testing of samples and thus deduce the composition of compounds. Infrared spectroscopy and a variety of other means of testing derived from a number of new molecular spectroscopy field, for example, chromatography and infrared spectroscopy for deepening the understanding of complex mixtures in a variety of components in the chemical structure of the system to create an opportunity; infrared spectroscopy and microscopy combined to form the infrared imaging technology for the study of non-homogeneous system of the morphology of the structure, due to the use of infrared spectroscopy can be characterized by the spectral band Because infrared spectroscopy can utilize its characteristic spectral bands to effectively distinguish between different compounds, which makes the method have a chemical contrast that is difficult to be matched by other methods. In addition, with the increasing progress of electronic technology, semiconductor detectors have been integrated, focal plane array detector has been commercialized, which effectively promotes the development of infrared imaging technology, but also for the future development of non-Fourier transform infrared spectrometer to create opportunities. With the development and wide application of synchrotron radiation technology, infrared spectrometer with synchrotron radiation light as a light source, due to the intensity of synchrotron radiation light is five orders of magnitude higher than the conventional light source, which can effectively improve the signal-to-noise ratio and resolution of the spectrum, it is worth pointing out that, in recent years, the free-electron laser technology provides a monochromatic, high-brightness, wavelength continuously adjustable new type of infrared light source, so that the combination with the near-field technology. In particular, free-electron laser technology has provided a new type of infrared light source with good monochromaticity, high brightness, and continuously adjustable wavelength, which can be combined with near-field technology to effectively improve the resolution and chemical contrast of infrared imaging technology.
Atomic Absorption Spectrometer
Atomic Absorption Spectrometer
The basic principle: the instrument radiates light with the characteristic spectral line of the element to be tested from the light source, and when it passes through the vapor of the specimen, it is absorbed by the atoms of the base state of the element to be tested in the vapor, and the degree of the radiation of the characteristic spectral line of the light is weakened to determine the content of the element to be tested in the specimen.
Usage:
Atomic absorption spectrometer can determine a variety of elements, flame atomic absorption spectrometry can be measured up to 10-9g/mL order of magnitude, graphite furnace atomic absorption method can be measured up to 10-13g/mL order of magnitude. Its hydride generator allows micro-trace determination of 8 volatile elements mercury, arsenic, lead, selenium, tin, tellurium, antimony and germanium.
Because of the sensitivity, accuracy and simplicity of the atomic absorption spectrometer, it is now widely used in metallurgy, geology, mining, petroleum, light industry, agriculture, medicine, health, food and environmental monitoring and other aspects of the analysis of the constant and micro-trace elements.
Atomic Absorption Spectrometer - Basic Knowledge
Ⅰ, the basic knowledge
1. The principle of the method
Atomic absorption refers to the gaseous state of the atoms on the characteristic spectral lines radiated by the same kind of atoms have the absorption phenomenon.
When radiation is projected onto an atomic vapor, if the energy corresponding to the wavelength of the radiation is equal to the energy required for the atom to jump from the ground state to the excited state, it will cause the atom to absorb the radiation, resulting in an absorption spectrum. Atoms in the ground state absorb the energy, and the outermost electrons make a jump from the low-energy state to the excited state.
2. Composition of the atomic absorption spectrometer
Atomic absorption spectrometer is composed of a light source, atomization system, spectroscopy system and detection system.
A light source
As a light source required to emit the sharp line spectrum of the element to be measured has sufficient intensity, small background, stability
Generally used: hollow cathode lamp electrodeless discharge lamp
B Atomizer (atomizer)
Can be divided into pre-mixed flame atomizer (premixed flame)
The atomizer can be divided into a pre-mixed flame atomizer, an atomizer, an atomizer, an atomizer and an atomizer, an atomizer, an atomizer, an atomizer, an atomizer and an atomizer. atomizer), graphite furnace atomizer (graphite furnace atomizer), quartz furnace atomizer (quartz furnace atomizer), cathode sputtering atomizer (cathode sputtering atomizer).
a flame atomizer: by the sprayer, pre-mixing chamber, combustor three parts
Characteristics: easy to operate, good reproducibility
b graphite furnace atomizer: is a class of the specimen placed in the wall of the graphite tube, graphite platform, carbon rods to hold samples of the small holes or graphite crucibles with electric heating to high temperature to achieve the atomization of the system. One of the tubular graphite furnace is the most commonly used atomizer.
Atomization procedure is divided into drying, ashing, atomization, high-temperature purification
Atomization efficiency: in the adjustable high-temperature specimen utilization of up to 100%
High sensitivity: its detection limit of 10-6 ~ 10-14
Less sample: suitable for the determination of refractory elements
c. Quartz furnace atomization system is the gas Analytes introduced into the quartz furnace at a lower temperature to achieve a method of atomization, also known as low-temperature atomization method. It is mainly used in conjunction with vapor generation (hydride generation, mercury vapor generation and volatile compound generation).
d. Cathodic sputtering atomizer is the use of positive ions generated by glow discharge bombardment of the cathode surface, from the solid surface directly into the measured elements into atomic vapor.
C Spectroscopic system (monochromator)
Consists of a concave reflector, a slit or a dispersive element
The dispersive element is a prism or a diffraction grating
The performance of a monochromator refers to the rate of dispersion, the resolution, and the light-collecting capability
D Detection system rate
Consisting of a detector (photomultiplier tube), an amplifier, a logarithmic converter, and a computer 3. Selection of optimum conditions
A Selection of absorption wavelength
B Selection of atomization operating conditions
a Selection of operating conditions for hollow cathode lamp (including preheating time, operating current)
b Selection of operating conditions for flame burner (amount of specimen lifted, type of flame, height of burner)
c Selection of optimum operating conditions for graphite furnace (inert gas, optimum atomization temperature)
C Selection of spectral passband
D Selection of operating conditions for detector photomultiplier tube
4. Interference and elimination methods
Interference is classified as follows: chemical, physical, ionization, spectral, and background interference
Chemical interference elimination Methods: change the flame temperature, adding releasing agents, adding protective complexing agents, adding buffers
The elimination of background interference: dual-wavelength method, deuterium lamp correction method, self-absorption method, the Seeman effect method