1 Atomic Absorption Spectrometer (AAS)
(1) Principle: The sample to be tested is atomized by an atomizer, and the test atom absorbs the light of the hollow cathode lamp of the element to be tested, so that the energy detected by the detector becomes lower, and the absorbance is obtained. The absorbance is directly proportional to the concentration of the element to be measured.
(2) The atomic absorption spectrometer (AAS) includes two parts: flame (FAAS) and graphite furnace (GFAAS).
●Detection limit: The detection limit of flame atomic absorption FAAS is 10-6, and the detection limit of GFAAS is 10-9.
●Sample analysis ability: The analysis speed of flame atomic absorption FAAS is about 1 minute for each element. The analysis speed is the fastest, but it can only be determined in a sequence of one element by element, and the element lamp must be changed every time an element is measured. Its detection range is generally 0.10～20×10-6. The analysis speed of GFAAS is 5 minutes for each element, and it can only be used for single element determination. The element lamp must be changed every time an element is measured. Its detection range is generally 0.03～50×10-9.
2 Inductively coupled plasma emission spectrometer (ICP-AES)
(1) Principle: Use the high temperature generated by argon plasma to completely decompose the atoms and ions in the excited state using the sample. Because the atoms and ions in the excited state are unstable, the outer electrons will transition from the excited state to a lower energy level, so Emit characteristic spectral lines. After the light is split through the grating, the intensity of a specific wavelength is detected by a detector, and the intensity of the light is proportional to the concentration of the element to be measured.
(2) Detection limit: The detection limit of most elements in ICP-AES is 10-6
(3) Sample analysis capability: The analysis speed of ICP-AES requires 1 to 2 minutes for each sample. All the elements in each sample will give results at the same time. There is no need to change the element lamp, and it is not a single element one by one. The analysis speed is much faster than atomic absorption, it can measure multiple elements at the same time, and its detection range is generally 10-6～10-2.
3 Instrument use and operating costs
(1) AAS has a narrow linear range and serious matrix interference. There are fewer analyzable elements than ICP-AES. Because FAAS uses acetylene gas, it must be supervised when using it. And ICP-AES and GFAAS, due to the modern automatic sampling design and the safety of using inert gas, can work unattended overnight.
(2) Both FAAS and GFAAS need to use element lamps. The price of domestic element lamps is about 200 to 400, and the price of imported element lamps is relatively high, but it has better stability and longer use time. The other cost of FAAS is acetylene gas, and GFAAS should calculate the cost of its graphite tube in addition to the cost of argon.
ICP-AES does not involve element lamps, and argon is required for the experiment. The average use of argon is about 8 hours per bottle and 4 hours for imported argon. The domestic ICP-AES only needs 4 9 medium argon to meet the ignition requirements, and the price is about 200 per bottle. The imported ICP requires five 9s of high-purity argon, and the cost is about 1000-2000. In addition, the safety factor of argon gas is higher than that of acetylene gas.
4 Usable lines and detection limit
(1) FAAS and GFAAS can only use atomic wires: Ni 232.003nm
(2) ICP-AES atomic wire and ion wire can be used, such as Ni 221.647 and 232.003, 231.604 can be used. The 221.647 itself is 10 times more sensitive than the 232.003 line, and the ICP is much more sensitive than the atomic absorption line.
AAS and Inductively Coupled Plasma Emission Spectrometer ICP have many detailed differences and differences. AAS and ICP technology can complement and cross each other, and ICP can also replace AAS, especially flame atomic absorption. However, the cost of ICP is relatively expensive, but the market ＆#118alue of graphite furnace atomic absorption is also quite high and the environmental requirements are relatively strict. From the user's point of view, the most important thing is to choose an instrument suitable for the unit according to the purpose of analysis, the scale of the laboratory and the quality of the personnel.
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