Instrument and its performance requirements for determination of emision spectrum
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Guiding Technical Documents of the Ministry of Electronics Industry of the People's Republic of China Instruments and Performance Requirements for Emission Spectroscopy Analysis SJ/Z3206.3-89
This standard applies to the main components, performance and specifications of some commonly used spectrometers, and is used to guide spectroscopic analysts to select instruments and determine their analysis methods. 1 Overview of Spectroscopic Instruments
The emission spectrometer used for sample component analysis consists of various parts such as excitation source, light source, focusing system, spectroscopic system, light receiving system and photometric system. The excitation source provides a certain form of energy to the light source, so that the sample is excited to emit light and produce characteristic spectral lines. The focusing system focuses the light and effectively shoots it into the spectroscopic system. The spectroscopic system colors the incident light into the spectrum of each element arranged by wavelength, and then shoots it to the light receiving system for recording. The photometric system measures the wavelength and intensity of the spectral lines of each element shot to the light receiving system, thereby determining the type and content of each element contained in the sample, so as to perform spectral qualitative and quantitative analysis. 2 Excitation source device
There are many types of excitation sources for spectral analysis, such as sparks, DC arcs, AC arcs, high-frequency plasmas and lasers, see SJ/Z3203.2-89 "Excitation sources for spectral analysis and their performance requirements". 3 Light source device
This device consists of electrodes and sample electrode holders. For the selection of electrode materials and the requirements for shape and size, see SJ/Z3206.6-89 (Shape and size of graphite electrodes for emission spectral analysis). The sample electrode holder is used to place rod-shaped sample electrodes, plate-shaped sample electrodes, solution sample electrodes, sample auxiliary electrodes and counter electrodes. 3.1 Rod-shaped sample electrode holder
This electrode holder can usually hold rod-shaped samples with a maximum diameter of 20 mm. The position of the electrode is adjusted by a projection device, and the size of the electrode gap is adjusted by a shading plate or an adjustment plate. To prevent the electrode from overheating, the fixture can be water-cooled. 3.2 Plate-like sample electrode holder
This electrode holder can usually hold plate-like samples with a minimum diameter of 10 mm and a thickness of less than 50 mm. The gap between the sample and the counter electrode can be adjusted by an adjustment device. Figures 1 and 2 list the shapes of two types of plate-like sample electrode holders. Approved by the Ministry of Electronics Industry of the People's Republic of China on February 10, 1989 and implemented on March 1, 1989
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Figure 1 An electrode holder for a normal pressure spectrometer
1-sample, 2-counter electrode, 3-sample table, 4-counter electrode loading and unloading part, safety valve, 6-exhaust port.
Figure 2 A vacuum spectrometer electrode holder
—protective quartz plate, 3—protective gas inlet, 4 counter electrode, 1 focusing lens, 2
5-sample, 6 protective gas outlet
3.3 Rotating electrode holder for liquid samples
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The sample auxiliary electrode of this electrode holder can rotate in the vertical direction, and the upper electrode can be replaced. The rotation speed is generally 5~15rPm (revolutions per minute). According to the viscosity of the sample solution and the analytical sensitivity, the rotation speed can be appropriately changed. Figure 3 is an example of a rotating electrode. A
Counter electrode
3.4 Atmosphere control device
Figure 3 Rotating electrode
010-20
In some analytical work, in order to eliminate the cyanide band, change the evaporation and excitation conditions of the sample, and improve the analytical sensitivity and accuracy: it is necessary to change the atmosphere around the electrode. Commonly used controlled atmosphere gases include fluorine, nitrogen, oxygen, hydrogen, phosphorus dioxide and their filtrates. Figure 4 is a quartz cyclone controlled atmosphere excitation chamber. 3
3.5 High-frequency plasma device
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Figure 4 Controlled atmosphere excitation chamber
Under the action of the high-frequency electromagnetic field, the gas is ionized to form plasma. The solution sample is sprayed into a mist by an atomizer. Then it is sent to the plasma torch shown in Figure 5 to be excited. 4
4 Focusing system
4.1 Basic considerations
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Isomorphic torch
Huiying circle
Cooling gas
Plasma gas
Test release aerosol
Figure 5 Inductively coupled high-frequency plasma torch In order to effectively inject the light from the light source into the beam splitter, the selection and adjustment of the focusing system must consider the following points
In order to obtain the best splitting ability, the width of the light beam should fill the dispersion system of the beam splitter. 4.1.1
4.1.2 In order to obtain the highest spectral line intensity, the light beam should fill the aperture of the beam splitter, that is, the diameter of the collimator of the beam splitter.
4.1.3 In order to reduce the influence of light source drift, a focusing system with a relatively small aperture should be selected. 4.2 Slit
The actual recorded spectral intensity and the actual resolution of the instrument are related to the slit width. In order to obtain the maximum resolution, the slit width W used should meet,
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where, f-focal length of collimator, cms
wavelength, nm.
d-effective width of dispersion element, cm.
Slits are of various types, such as fixed, single-side adjustable, and double-side adjustable. The general requirements for slits are as follows:
The two sides of the slit should be strictly parallel when stationary or open and closed. 4.2.1
4.2.2The two sides of the slit should be optical straight lines, and the curved slit should be a smooth curve. There should be no notches, scratches or dirt on the slit.
4.2.3The two sides of the slit should be strictly kept in the same plane. 4.2.4 For slits with adjustable width, the width should be continuously adjustable within the range of 0 to 100 μm. The opening and closing mechanism should be very sensitive and accurate, and the accuracy of repeated adjustment should be within 1 μm. 4.2.5 The adjustable slit should be opened by the adjusting screw and closed by the spring tension. It should not be directly pushed by the screw or driven by the plate.
4.3 Imaging method
The imaging system of the focusing device is generally composed of a lens, a slit and a collimator. There are several imaging methods: 4.3.1 Slit imaging method
This imaging method focuses the image of the light source on the slit, so that the spectral intensity distribution of the light source in the vertical direction appears on the focal plane of the beam splitter. In order to avoid this phenomenon, a Hartmann optic is placed in front of the slit to reduce the height of the slit so that only a part of the light from the light source enters the beam splitter. Another method is to let the focus of the lens slightly deviate from the slit. The optical system of the slit imaging method is shown in Figure 6. 2
Figure 6 Single lens slit imaging system
1 Light source, 2--lens, 3 Slit, 4--collimator 4.3.2. Collimator imaging method
This imaging method requires that the image of the light source falls on the collimator, so it is necessary to evenly illuminate the slit, and the light source is exactly at the light transmission position. Photoelectric spectrometers generally use this imaging method. Figure 7 is the optical system of the collimator imaging method. 6
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Figure? Single lens collimator imaging system
1-Light source, 2-lens, 3 Slit, 4-Collimator 4.3.3 Cylindrical lens imaging method
This imaging method is used to make the rectangular diffraction grating evenly illuminated. In this optical system, in order to observe and adjust the image of the light source, a projection system must be installed on the electrode frame. The optical system of the cylindrical lens imaging method is shown in Figure 3.
Figure 8 Cylindrical lens imaging system
1—light source, 2, 3—cylindrical lenses, 4—slit, 5—collimation 4.3.4 Intermediate imaging method
This imaging method can make the slit illuminate evenly. In addition, by adjusting the position of the light source using the intermediate light width, any part of the light source can be selected. Due to the drift of the light source, the light will be obliquely incident on the beam splitter, which can be overcome by using a filter lens focusing system. The optical system of the intermediate imaging method is shown in Figure 9. Figure 9 Intermediate imaging system
Light source, 2, 4, 5—lenses, 3—
—intermediate light source, 6
Slit, 7
—collimator
5 Spectral system
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Dispersive elements that decompose composite light into monochromatic light include prisms and gratings. Prism materials include crystal, fused quartz, and glass. Gratings include plane gratings, concave gratings, step gratings, etc. Dispersive elements are the core part of the spectrometer.
5.1 Prism
Prism dispersion is based on the principle of light refraction. Its types and combinations are mainly as follows: 5.1.160° Corneus mirror
It is composed of two 30° prisms made of different crystalline states (left-handed and right-handed) quartz in optical contact, which can offset the optical rotation of quartz, see Figure 10.
5.1.230° Littrow prism
Right-handed crystal
Left-handed crystal
Figure 10 Cauignau prism
Aluminum is plated on one vertical surface of the prism. After the light enters the prism, it is reflected back by the aluminum-plated back surface and passes through the prism again, thus achieving the effect of a 60° prism and having a racemic light effect, as shown in Figure 11. 8
5.1.3 Constant deflection prism
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1 Littrow prism
For any wavelength of light, as long as it is in the minimum deflection position, the minimum deflection angle of the outgoing ray is always equal to 90°. Abbe prism belongs to this type, see Figure 12. 5.1.4 Festerling prism system
Figure 12 Constant deflection prism
It consists of two identical isosceles prisms (vertex angle 63°) and an Abbe prism in the middle. Its character dispersion is three times that of a prism with the same vertex angle. The disadvantage is that the total optical path is longer, see Figure 13. 9
5.1.5 Amici direct view prism
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Figure 13 Festerling prism system
It consists of three prisms glued together. The left and right two are symmetrical to each other. The refractive index and dispersion of the middle prism are larger than those of the two sides. This prism has a small character dispersion and is generally used in small spectrometers, see Figure 14. nz
Figure 14 Amici direct-view prism
5.2 Main performance of prism spectrograph
The main performance of a typical prism spectrograph is listed in Table 1: Table 1 Main performance of prism spectrograph
Indicators
Medium-sized quartz spectrograph
Large quartz spectrograph
Quadrangular prism quartz spectrograph
Wavelength range
200~800
210~800
Dispersion system
30° Cornewac prism
Collimator and image
Focus of objective lens
580~700
30° Littrow prism 1500~1700
Four 60° prisms
Reciprocal line dispersion nm/mm
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5.2.1 A medium-sized spectrograph can capture the spectrum within the wavelength range of 200~800mm on a 240mm long photosensitive plate, and all optical components are fixed. The wavelength scale installed in the instrument can be captured on the photosensitive plate at the same time, which is very beneficial in the qualitative analysis of the spectrum.
5.2.2 A large spectrograph has a larger dispersion rate, and the width from the wavelength of 200~800mm is about 670mm. The three parameters of this instrument, namely, the position of the prism, the distance between the lens and the photosensitive plate, and the tilt angle between the lens optical axis and the photosensitive plate, can be changed by rotating the shuttle mirror, so that spectral lines of any wavelength range can be captured on a photosensitive plate. 5,2.3 The four-prism spectrograph also has a large dispersion rate, and its darkroom has a short focal length, high brightness, and high resolution. 5.8 Grating
Grating is an optical element that disperses composite light into a spectrum based on the principle of multi-slit diffraction. It is formed by spraying an aluminum layer on a flat or concave glass and engraving a large number of parallel, equal-width, and equal-distance grooves. There are many ways to assemble the grating, slit, imaging system, and receiving components into a grating spectrometer. Among them, concave gratings include: Bosing-Runge type, Eagle type, Wadsworth type, etc., and plane gratings include, Cherny-Terner type and Albert type, etc., see GB9295-88 (Terms of Emission Spectrum Analysis). 5.4 Main performance of grating spectrograph
The main performance of a typical grating spectrograph is listed in Table 2: Table 2 Main performance of grating spectrograph
Performance indicators
Watzwisz type
Chorney-Terrejunction type
Albert type
Traveling grating
Strip/mm
Inverse line color
Photographic plate or
Film length
Wavelength range that can be photographed at one time
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5.4.1 The Wattswiss type spectrograph can obtain spectral line images with very small astigmatism within a range equal to one-sixth of the distance from the diffraction grating to the photographic plate. Since the relative position of the diffraction grating and the photosensitive plate cassette is fixed and the focal plane is a curved surface, photosensitive film is used instead of the photosensitive plate. 5.4.2 The diffraction grating of the Choerny-Terner spectrograph can be rotated to capture spectral lines of different wavelength ranges, and its aberration is also very small.
5.4.3 The Albert spectrograph has two modes: the slit and the focal plane are arranged on the same horizontal plane (side by side) and arranged in a vertical direction (upper and lower). The instrument has extremely small astigmatism and a simple mechanical structure. The working wavelength range can be changed by changing the grating rotation angle.
6 Receiving and photometric system
The spectral lines emitted by the spectroscopic system can be received and measured in three different ways, namely, visual method, spectrophotometry and photoelectric direct reading method.
6.1 Spectrum viewing mirror
Visual method spectral analysis uses the human eye as the receiver of the spectrum, and the instrument used is called a spectrum viewing mirror. The spectroscope can introduce the non-commercial parts in the visible light range into the field of view, and compare the spectral line brightness of the measured elements and matrix elements appearing in the field of view to perform semi-quantitative analysis.
The spectroscope should meet the following conditions:
6.1.1 The dispersion system generally adopts a self-collimating optical system, and there is also a single-light path system with two or three prisms. 6.1.2 The distance between the focal points of the collimator and the observation mirror is 200~300mm. 6.1.3 The wavelength of the analysis line should mostly be around 550nm to adapt to the eye's sensitivity to visible light. 6.1.4 The resolution of the spectroscope is 0.05~0.1nm. 6.1.5 It has a lightweight arc generating device, and is equipped with a shading plate to block the arc ultraviolet rays to protect the eyes and a protective plate to protect the lens from damage by splashes. Figure 15 is a schematic diagram of a spectroscope.
Figure 15 Schematic diagram of the optical system of the spectroscope
1-sample, 2-auxiliary electrode, 3-prism, 4-lens, 5-slit, 6-objective lens, 7-optical lens, 8-image transfer lens, 9-optical lens, 10-microscope objective lens, 11-heliostat, 12-light output lens8 Grating
Grating is an optical element that disperses composite light into a spectrum based on the principle of multi-slit diffraction. It is made by spraying an aluminum layer on a flat or concave glass and then engraving a large number of parallel, equal-width, and equal-distance grooves. There are many ways to assemble the grating, slit, imaging system, and receiving components into a grating spectrometer. Among them, concave gratings include: Bosing-Runge type, Eagle type, Wadsworth type, etc., and flat gratings include: Cherny-Terner type and Albert type, etc., see GB9295-88 (Terminology of Emission Spectrum Analysis). 5.4 Main performance of grating spectrograph
The main performance of a typical grating spectrograph is listed in Table 2: Table 2 Main performance of grating spectrograph
Performance indicators
Watzwisz type
Chorney-Terrejunction typebzxz.net
Albert type
Traveling grating
Strip/mm
Inverse line color
Photographic plate or
Film length
Wavelength range that can be photographed at one time
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5.4.1 The Wattswiss type spectrograph can obtain spectral line images with very small astigmatism within a range equal to one-sixth of the distance from the diffraction grating to the photographic plate. Since the relative position of the diffraction grating and the photosensitive plate cassette is fixed and the focal plane is a curved surface, photosensitive film is used instead of the photosensitive plate. 5.4.2 The diffraction grating of the Choerny-Terner spectrograph can be rotated to capture spectral lines of different wavelength ranges, and its aberration is also very small.
5.4.3 The Albert spectrograph has two modes: the slit and the focal plane are arranged on the same horizontal plane (side by side) and arranged in a vertical direction (upper and lower). The instrument has extremely small astigmatism and a simple mechanical structure. The working wavelength range can be changed by changing the grating rotation angle.
6 Receiving and photometric system
The spectral lines emitted by the spectroscopic system can be received and measured in three different ways, namely, visual method, spectrophotometry and photoelectric direct reading method.
6.1 Spectrum viewing mirror
Visual method spectral analysis uses the human eye as the receiver of the spectrum, and the instrument used is called a spectrum viewing mirror. The spectroscope can introduce the non-commercial parts in the visible light range into the field of view, and compare the spectral line brightness of the measured elements and matrix elements appearing in the field of view to perform semi-quantitative analysis.
The spectroscope should meet the following conditions:
6.1.1 The dispersion system generally adopts a self-collimating optical system, and there is also a single-light path system with two or three prisms. 6.1.2 The distance between the focal points of the collimator and the observation mirror is 200~300mm. 6.1.3 The wavelength of the analysis line should mostly be around 550nm to adapt to the eye's sensitivity to visible light. 6.1.4 The resolution of the spectroscope is 0.05~0.1nm. 6.1.5 It has a lightweight arc generating device, and is equipped with a shading plate to block the arc ultraviolet rays to protect the eyes and a protective plate to protect the lens from damage by splashes. Figure 15 is a schematic diagram of a spectroscope.
Figure 15 Schematic diagram of the optical system of the spectroscope
1-sample, 2-auxiliary electrode, 3-prism, 4-lens, 5-slit, 6-objective lens, 7-optical lens, 8-image transfer lens, 9-optical lens, 10-microscope objective lens, 11-heliostat, 12-light output lens8 Grating
Grating is an optical element that disperses composite light into a spectrum based on the principle of multi-slit diffraction. It is made by spraying an aluminum layer on a flat or concave glass and then engraving a large number of parallel, equal-width, and equal-distance grooves. There are many ways to assemble the grating, slit, imaging system, and receiving components into a grating spectrometer. Among them, concave gratings include: Bosing-Runge type, Eagle type, Wadsworth type, etc., and flat gratings include: Cherny-Terner type and Albert type, etc., see GB9295-88 (Terminology of Emission Spectrum Analysis). 5.4 Main performance of grating spectrograph
The main performance of a typical grating spectrograph is listed in Table 2: Table 2 Main performance of grating spectrograph
Performance indicators
Watzwisz type
Chorney-Terrejunction type
Albert type
Traveling grating
Strip/mm
Inverse line color
Photographic plate or
Film length
Wavelength range that can be photographed at one time
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5.4.1 The Wattswiss type spectrograph can obtain spectral line images with very small astigmatism within a range equal to one-sixth of the distance from the diffraction grating to the photographic plate. Since the relative position of the diffraction grating and the photosensitive plate cassette is fixed and the focal plane is a curved surface, photosensitive film is used instead of the photosensitive plate. 5.4.2 The diffraction grating of the Choerny-Terner spectrograph can be rotated to capture spectral lines of different wavelength ranges, and its aberration is also very small.
5.4.3 The Albert spectrograph has two modes: the slit and the focal plane are arranged on the same horizontal plane (side by side) and arranged in a vertical direction (upper and lower). The instrument has extremely small astigmatism and a simple mechanical structure. The working wavelength range can be changed by changing the grating rotation angle.
6 Receiving and photometric system
The spectral lines emitted by the spectroscopic system can be received and measured in three different ways, namely, visual method, spectrophotometry and photoelectric direct reading method.
6.1 Spectrum viewing mirror
Visual method spectral analysis uses the human eye as the receiver of the spectrum, and the instrument used is called a spectrum viewing mirror. The spectroscope can introduce the non-commercial parts in the visible light range into the field of view, and compare the spectral line brightness of the measured elements and matrix elements appearing in the field of view to perform semi-quantitative analysis.
The spectroscope should meet the following conditions:
6.1.1 The dispersion system generally adopts a self-collimating optical system, and there is also a single-light path system with two or three prisms. 6.1.2 The distance between the focal points of the collimator and the observation mirror is 200~300mm. 6.1.3 The wavelength of the analysis line should mostly be around 550nm to adapt to the eye's sensitivity to visible light. 6.1.4 The resolution of the spectroscope is 0.05~0.1nm. 6.1.5 It has a lightweight arc generating device, and is equipped with a shading plate to block the arc ultraviolet rays to protect the eyes and a protective plate to protect the lens from damage by splashes. Figure 15 is a schematic diagram of a spectroscope.
Figure 15 Schematic diagram of the optical system of the spectroscope
1-sample, 2-auxiliary electrode, 3-prism, 4-lens, 5-slit, 6-objective lens, 7-optical lens, 8-image transfer lens, 9-optical lens, 10-microscope objective lens, 11-heliostat, 12-light output lens
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