Some standard content:
National Standard of the People's Republic of China
General rules for atomic absorption spectrometric analysis1Subject content and scope of application
This standard specifies the general rules for quantitative analysis using source-absorption spectrometer. This standard is applicable to the quantitative analysis of chemical elements from normal disk to decay disk using atomic absorption spectrometer. 2 Reference standards
GB/T 4470 Flame emission atomic absorption and atomic spectroscopy - New terminology GB/T 4471 Test methods for chemical products - Precision - Determination of repeatability and reproducibility of inter-laboratory tests GB 6682 Specification and test methods for water for analytical laboratories GB 6819 Dissolved acetylene
3 Terminology
3.1 Flame atomic absorption spectrometry - Flat atomic absorption spectrometry GB/T 1533794
A method in which the element to be analyzed in the sample is converted into free atoms by flame, and the content of the chemical element is determined by measuring the absorption of characteristic electromagnetic radiation by the ground state atoms of the element in the vapor phase. 3.2 Flameless atomic absorption spectrometry - Flameless atomic absorption spectrometry - A method in which the element to be analyzed in the sample is converted into free atoms by non-flame methods (such as electric heating, laser chemical reaction, etc.), and the content of the chemical element is determined by measuring the absorption of characteristic electromagnetic radiation by the ground state atoms of the element in the vapor phase. 3.3 Electrothermal atomic absorption spectrometry Electrothermal atomic absorption spectrometry is a method of converting the element to be analyzed in the sample into free atoms by using electric heat (such as graphite furnace, etc.), and determining the content of the chemical element by measuring the absorption of characteristic electromagnetic radiation by the ground state atoms of the element in the vapor phase. 3.4 Hydride generation atomic absorption spectrometry is a method of determining the content of the chemical element by measuring the absorption of characteristic electromagnetic radiation by the ground state atoms of the element in the vapor phase after the element to be analyzed is reduced to generate hydride, which is then decomposed into free atoms of the element by heating (electric heating or flame). 3.5 Mercury by cald vapour generation atomic absorption spectrometry
The mercury in the sample to be analyzed is reduced to free atoms, and the mercury content is determined by measuring the absorption of characteristic electromagnetic radiation by the ground state atoms in the vapor phase. 3.6 Sheath gas
Inert gas used to prevent oxidation of the measured elements and materials around the atomization system during analysis operations. Note: Other terms refer to GB/T 4470. 4. Principle of the method: Electromagnetic radiation with characteristic wavelength of the element to be measured is radiated from the light source. When the sample gas is produced by atomization system such as flame or electric heating, the National Technical Supervision Bureau approved it on December 22, 1994 and implemented it on October 1, 1995. GB/T 15337-94. Under certain experimental conditions, the relationship between the absorbance value and the concentration of the element to be measured in the sample conforms to the law of light absorption: A - logpo/ K -L*c Where: A—absorbance
——incident electromagnetic radiation flux:
omitted——transmitted electromagnetic radiation flux:
K—absorption coefficient, which is a constant under certain experimental conditions; L—absorption optical path length,
—concentration of the element to be measured.
This law can be used to perform fixed plate analysis.
5 Reagents and Materials
+（1）
When using atomic absorption spectrometry for macro analysis, the water used should meet the specifications of secondary water in GB6682. When conducting trace element analysis, the water used should meet the specifications of intermediate water in GB6682. When storing and using, it should comply with the relevant provisions of GB6682. 5.2 Reagents
The purity of the reagents used should be analytically pure or better, and the reagent blank should be checked before use. The reagent blank value must meet the requirements.
Inorganic acid is a commonly used solvent. It often contains a small amount of metal elements and should be strictly checked before use. If necessary, it must be purified by sub-boiling distillation. The distillation apparatus is shown in Appendix C (reference).
The preparation of the latent solution should meet the following requirements:
. Appropriate solvents should be selected, and the prepared solution should not have any insoluble matter precipitated. The solution should be stored in a very clean and suitable container.
b. The reagents for preparing standard solutions should be prepared with substances of high purity, accurate composition and chemical formula, and stable properties. If high-purity metals are used for preparation, the metals should be cleaned with acid to remove the surface oxide layer before dissolving. c. The mass concentration of the standard stock solution is generally 1 mg/mL. A small amount of inorganic salts should be added to the standard solution of some elements to facilitate storage. Standard solutions with a mass concentration of less than 1 μg/mL are generally prepared on the spot. Standard solutions with a concentration of more than 1 μg/mL can be kept for several days or longer. The storage time varies for different elements. Standard solutions and standard stock solutions should be stored in tetrafluoroethylene or high-pressure polyethylene plastic containers to prevent concentration changes or contamination. Some solutions that are easily decomposed by light (such as Au and Ag) should be stored in brown corrugated glass bottles. If necessary, they should be stored in a clean, low-temperature and dark place to prevent light from changing the concentration. 5.3 Gas
The fuel gas used for the flame is usually acetylene, hydrogen, etc., and the combustion-supporting gas is air, oxygen and nitrous oxide, etc. Gas products that meet the requirements of relevant standards should be used. When using compressed air, dust should be fully removed. The protective gas used for the flameless method, such as hydrogen, nitrogen and hydrogen, should not contain the element to be measured. 6 Instruments
6.1 Main components of the instrument
The atomic absorption spectrometer is mainly composed of four parts: light source system, atomization system, spectroscopic system, detection and display system, and background correction system, automatic sampling system, etc.
6.1.1 Light source system
6.1.1.1 Light source lamp
It is the light source used for analysis. It should be able to emit electromagnetic radiation of the element to be measured with a spectrum as narrow as possible and a sufficiently high intensity. Commonly used light source lamps are hollow cathode lamps and electrodeless discharge lamps.
GB/T 15337--94
The hollow cathode lamp can emit sharp lines of characteristic spectral lines of the elements to be filled. It is the most widely used sharp line light source in atomic absorption spectroscopy. The electrodeless discharge lamp is specially used for the analysis of elements such as tantalum, selenium, tin, antimony, lead, chrysene, ruthenium and tellurium. The intensity of the characteristic spectral lines of the elements it emits is stronger than that of the hollow cathode lamp, and the spectral line width is narrow, the self-absorption broadening is small, the spectral purity is good, and it can improve the sensitivity and detection limit of general analysis, but the general stability and life are not as good as the hollow cathode lamp.
6.1.1.2 Eastern lamp
It is a light source for background correction and belongs to a continuous spectrum lamp. It can emit a continuous spectrum near 190nm to 430nm. 6.1.1.3 Light source lamp power supply
The light source lamp power supply can light the light source lamp and stabilize its light intensity. 6.1.2 Atomization system
Its function is to convert the elements to be measured in the sample into ground state atoms so as to realize atomic heat absorption measurement. Commonly used atomization systems include: flame source atomization system, electrothermal atomization system, hydride generation atomization system and cold vapor generation atomization system.
6.1.2.1 Flame atomization system
The flame atomization system consists of main components such as atomizer, premixer, burner, etc. Its function is to atomize the test solution into aerosol, then mix it with fuel gas, and enter the flame generated by the burner to dry, evaporate, and dissociate the sample, and finally convert the elements to be measured into ground state atoms. Commonly used gases in the flame atomization system include acetylene, oxygen, air, oxygen, nitrous oxide and oxygen. The flame atomization system should have a certain atomization efficiency, be corrosion-resistant, have high atomization efficiency, low noise and good flame stability, and should have safety protection devices, waste liquid discharge devices, etc. 6.1.2.2 Electrothermal Atomization System
The electrothermal atomization system consists of an electric heating furnace and a power supply. . Electric heating furnace: Its function is to dry and ashed the sample melt, and finally make the element to be tested form ground state atoms. Graphite is generally used as the heating element, and protective gas is passed through the furnace to prevent oxidation and transport sample vapor. . Power supply: The heating element of the electric heating furnace can be heated to the required temperature in sections or continuously. 6-1-2.3 Hydride generation atomization system
The hydride generation atomization system consists of a hydride generator and an atomic absorption cell. It is used for the determination of elements such as stearic acid, selenium, antimony, lead, bismuth, zirconium and ruthenium.
E: Hydride generator: Its function is to reduce the element to be measured into hydride in an acidic medium, and then introduce it into the atomic absorption cell by carrier gas.
Atomic absorption cell: It consists of a quartz tube, a heater and a temperature controller, and its function is to heat and decompose the hydride into ground state atoms.
6-1-2.4 Cold vapor generation atomization system
The cold vapor generation atomization system consists of a mercury vapor generator and an atomic absorption cell, and it is dedicated to the determination of mercury elements. : Mercury vapor generator: Its function is to reduce the mercury ions in the test solution into mercury vapor, and then introduce it into the atomic absorption cell by carrier gas.
b. Atomic absorption cell: a quartz atomic absorption cell with right windows at both ends and gas flow. 6.1.3 Spectroscopic system
The spectroscopic system is composed of a spectroscopic element, incident and exit narrow relays, and several reflectors. The wavelength range is generally 190.0~900.0nm. Its function is to separate the required electromagnetic radiation from the electromagnetic radiation emitted by the light source. 6.1.4 Detection system
The detection system is composed of a detector, a signal processor, and an indicator recorder. Its function is to convert the micro-light signal into a measurable electrical signal through the detector, separate the GB/T 15337--94
electrical signal required for measurement through the signal processor, and read the measured value expressed as absorbance or element concentration through the indicator recorder. It should have high sensitivity and good stability, and be able to track the rapid changes of the absorption signal in a timely manner. 6.1.5 Background correction system
There are four commonly used background correction systems:. The continuous light source background correction system
uses the difference between the total absorbance value of atomic absorption and background absorption measured by the sharp line spectrum of hollow cathode lamp radiation and the absorbance value of background absorption measured by the continuous spectrum of continuous light source radiation to obtain the atomic absorbance value of the element to be measured, thereby achieving the purpose of subtracting the background. Commonly used continuous light sources include chlorine lamps, which are suitable for wavelengths within the range of 190~～430nm. It is suitable for instruments equipped with continuous spectrum correction devices. b. Zeeman effect background correction system
uses the Zeeman effect to subtract the background. There are many Zeeman modulation methods. For constant magnetic field transverse Zeeman modulation, a constant magnetic field is applied to the atomization system, and the direction of the magnetic field is perpendicular to the direction of the light beam. Under the action of strong field avoidance, the atomic absorption line is split into a component whose polarization direction is parallel to the magnetic field and a component whose polarization direction is perpendicular to the magnetic field. The light from the light source is transformed into polarized light under the action of the polarizing element. The polarized light parallel to the magnetic field and perpendicular to the magnetic field alternately passes through the atomization system. The polarized component parallel to the magnetic field has the same wavelength and polarization direction as the absorption line Zeeman splitting element component, and produces resonance absorption. The absorbance values of the source absorption and background absorption are measured. The polarized component perpendicular to the magnetic field and the absorption line Zeeman splitting element component have different polarizations and are not absorbed by the element component, but only by the background. The background absorbance value is measured. The absorbance values of the two measurements are subtracted to obtain the absorbance value of the element to be measured, thereby achieving the purpose of subtracting the background. It can correct the background in the entire band.
It is suitable for instruments equipped with Zeeman effect background correction devices. c. Self-absorption effect background correction system
A method of using a double pulse powered hollow cathode lamp to subtract the background, that is, using a low current pulse powered hollow cathode lamp to generate an emission line to measure the absorbance of atomic absorption and background absorption, using a high current pulse to make the hollow cathode lamp produce a broadened spectrum with strong self-absorption, and measuring the absorbance of background absorption. The two measured absorbance values are subtracted to obtain the atomic absorbance value of the element to be measured, thereby achieving the purpose of subtracting the background. It is suitable for instruments equipped with a self-absorption effect background correction system. d. Non-absorption line background correction system
Using absorption lines to measure the absorbance of atomic absorption and background absorption, using non-absorption lines to measure the absorbance of background absorption, and comparing the absorbance values twice to obtain the atomic absorbance value of the element to be measured, thereby achieving the purpose of subtracting the background. Note that the selected non-absorption line should comply with the following principles: It must be confirmed that the selected non-absorption line is indeed a non-absorption line. b The wavelength of the selected non-absorption line should be as close to the absorption line as possible, and the difference between the two should be within 10.0nm. Center. The non-absorption line emitted by the light source must have sufficient intensity to ensure a good signal-to-noise ratio. Background correction can only be performed according to this method when the instrument does not have a background correction system. 6.1.6 Accessories
Automatic sampling system and other equipment can be added as needed. 6.2 Main performance requirements and measurement methods of the instrument 6.2.1 Wavelength indication error
refers to the difference between the wavelength indication of the element sensitive absorption line and the wavelength standard value, which should not be greater than ±0.5nm. 6.2.2 Wavelength repeatability
The ability of the instrument to give consistent readings for a certain wavelength measurement value without considering the systematic error, which should not be greater than 0.3nm.
6-2.3 Resolution
Resolution refers to the ability of the instrument to separate the element sensitive absorption line from the near spectral line. When the instrument spectral bandwidth is U.2nm, it should be able to distinguish the double lines of 279.5nm and 279.8nm of manganese. 6.2.4 Baseline stability
GB/T15337-94
refers to the ability of the instrument to maintain the stability of its absorbance value within a period of time. Within 30 minutes, the maximum zero drift of its static baseline stability should not be greater than ±0.006A and the maximum instantaneous noise should not be greater than 0.006A, and the maximum zero drift of its ignition baseline stability should not be greater than ±0.008A and the maximum instantaneous noise should not be greater than 0.008A.6.2.5 Edge energy
It reflects the ability of the instrument to collect light from the light source at the edge wavelength. At the edge wavelength of the instrument, the peak-to-background ratio of the 193.7 nm to 852.1 nm harmonic line should be measured at a rate of less than ±2%, and the instantaneous noise should be less than 0.03A within 5 minutes. 6.2.6 Detection limit Cc<=3) or QL(3)) refers to the minimum content of an element in a sample solution that can be detected with a certain degree of confidence. It is related to the instrument, the element to be measured and the analytical method. When the element and analytical method are given, it is a compatibility indicator of the instrument. When the instrument is measured by flame atomic absorption spectrometry, it should not be greater than 0.02/mL. When cadmium is measured by graphite furnace atomic absorption spectrometry, it should not be greater than 4Pg. 6.2.7 Characteristic concentration (or characteristic quantity)
is an indicator that reflects the sensitivity performance of the instrument. It is related to the instrument, the element to be measured and the analytical method. That is, under given test conditions, it is equivalent to the concentration (or mass) of the element to be measured that can produce 1% absorption signal (i.e. 0.0044A absorbance value). When the instrument is measured by flame atomic absorption spectrometry, it should not be greater than 0.04 μg/mL; when it is measured by graphite furnace atomic absorption spectrometry, it should not be greater than 2Pg. 6.2.8 The precision of the instrument refers to the degree of consistency between the results of repeated measurements of the same sample under given test conditions. It is related to the instrument, the element to be measured and the analytical method. When the instrument uses flame atomic absorption spectrometry to measure copper, it should not be greater than 1.5%, and when using stone-based furnace atomic absorption spectrometry, it should not be greater than 7%. Note: For the determination methods of the main performance of the instrument group, see Appendix A (Supplement). 7 Determination When determining, direct determination or interpretation or pre-enrichment test must be adopted according to the characteristics of the sample and the instrument. The element to be measured must not be lost or contaminated when separating the matrix. After separation, the residual amount of the matrix should not interfere with the determination of the element to be measured, nor should it corrode the instrument. The corresponding blank test solution and calibration solution must be prepared at the same time. 7.1 Selection of determination method According to the characteristics and content of the sample and the element to be measured, one of the following determination methods can be selected. Flame atomic absorption spectrometry.
Electrothermal atomic absorption spectrometry
Hydride generation atomic absorption spectrometry.
d. Cold vapor generation atomic absorption spectrometry for mercury atom measurement. 7.2 Selection of measurement conditions
7.2.1 Selection of common conditions for flame and flameless atomic absorption spectrometry 7.2-1.1 Analysis line
Select spectral lines that are not interfered with and have moderate pseudo-luminosity. The wavelength values of the analysis lines of commonly measured elements are shown in Appendix B. 7.2.1.2 Light source lamp current value
On the premise that the whole machine has sufficient stability, the lamp current with the best signal-to-noise ratio should be selected. Selection method, measure the absorbance of a certain standard solution under different lamp currents, draw a relationship curve between lamp current and absorbance, and select a lamp current with large absorbance value and good stability.
7.2-1.3 Passband width
On the premise of ensuring sufficient energy, select the narrowest possible passband width.
GB/T15337-94
Generally, for simple spectral line elements, use a wider passband, multi-harmonic line elements need to use a narrower passband, and the incident electromagnetic radiation cannot be too 7.2.1.4 Absorbance reading range
In order to reduce the error of photometric measurement, the absorbance reading is generally selected between 0.1 and 0.6. If necessary, the concentration of the solution or the optical path length or the range can be adjusted.
7.2.2 Selection of determination conditions for flame atomic absorption spectrometry 7.2.2.1 Flame type
According to the properties of the analysis sample and the specific measured element, an oxidizing flame, a chemometric flame or a reducing flame can be selected. 7.2.2.2 The mixing ratio of fuel gas and supporting gas
It should be selected according to the properties of the sample and the sensitivity and stability of the measured element. The selection method is: Under the condition of fixed supporting gas (or fuel gas), change the flow rate of fuel gas (or supporting gas), measure the absorbance of standard solution at different flow rates, draw the relationship curve between absorbance and fuel-support ratio, and select the fuel-support ratio with large absorbance value and relatively stable flame. 7.2.2.3 Burner height and angle
Adjust the burner height so that the electromagnetic radiation radiated by the light source passes through the part with the largest concentration of ground state atoms in the flame. The selection method is: Under the condition of fixed fuel-support ratio, measure the absorbance of standard solution at different burner heights, draw the burner height and absorbance curve, and select the burner height with large absorbance value. The angle of the burner determines the length of the absorption path. According to the content of the element to be measured, select the appropriate absorption path length. 7.2.3 Selection of conditions for graphite furnace electron absorption spectrometry 7.2.3.1 Drying temperature (or current value) and time The main function of drying is to remove the solvent from the sample and avoid splashing of sample droplets. The starting temperature should be slightly lower than the boiling point of the solvent. 7.2.3.2 Ashing temperature (or current value) and time The main function of ashing is to decompose organic matter or volatilize salts in the matrix to reduce or eliminate background absorption and mutual interference between elements during atomization. The selected ashing temperature (or current value) and time should fully remove the matrix of the sample while preventing the loss of the measured element due to volatilization. Selection method: Draw a curve of absorbance versus ashing temperature or time, and select the highest ashing temperature or time with the largest absorbance value. 7.2.3.3 Atomization temperature (or current value) and time The function of atomization is to atomize the element to be measured. The atomization temperature is determined by the nature of the element to be measured. The selected atomization temperature (or current value) and time should be such that the measured element is fully atomized. The atomization temperature should be as low as possible to extend the service life of the stone fireplace. Selection method: the lowest temperature and time to achieve the maximum absorbance value. 7.2.3.4 The type and flow rate (or pressure) of the protective gas should be selected in accordance with the principle of not oxidizing the heating element. The commonly used protective gas for graphite furnaces is hydrogen. The flow rate (or pressure) should be selected based on the properties of the analyzed sample, the sensitivity and stability of the measured element, etc. 7.2.3.5 Graphite tube
Commonly used graphite tubes include: ordinary stone wall tube, pyrolytic coated graphite tube, full pyrolytic graphite tube, etc., which can be selected according to needs and possibilities.
7.2.4 The detection limit and characteristic concentration of the measured element can be found in 6.2.6, 6.2.7 and Appendix A. 7.2.5 Methods for eliminating or reducing various interferences in determination 7.2.5.1 Methods for eliminating ionization interference
Add ionization buffer to the analytical sample solution. 7.2.5.2 Methods for eliminating physical interference
GB/T 15337-94
Make the composition of the calibration solution consistent with that of the sample solution. 7.2.5.3 Methods for eliminating chemical interference
The methods for eliminating chemical interference mainly include:
. Add chemical reagents for eliminating interference, such as release agents, complexing agents, surfactants, etc. b. Add excessive amounts of interfering elements to make the interference effect reach the saturation point to eliminate or inhibit the influence of interfering elements. Note: This method is used under the premise that the interfering elements produce positive interference or when high concentrations of interfering substances exist, the absorption of the element to be measured will not be significantly reduced. c. High temperature flame method.
d. Add matrix modifier. bzxz.net
Chemical separation method.
7.2.5.4 Methods for eliminating spectral interference 1
1 Background correction method
Background correction methods can use continuous light source, plug effect, non-absorption line, self-absorption and other methods. See Appendix B (Supplement) for non-absorption lines (correction lines) used for background correction. Alternatively, spectral lines without spectral interference can be used as analysis lines. 7. 3 Quantitative method
Use the absorbance value obtained by the indicating recorder to calculate the concentration of the measured element in the sample solution as follows. However, no matter which of the following methods is used, the plotting of the relationship curve between absorbance and concentration (correction curve) must be carried out simultaneously with the determination of the sample solution. 7.3.1 Standard Curve Method
According to the provisions of the relevant standards, under the possible conditions of the instrument, prepare five or more calibration solutions in series. Under the specified instrument conditions, adjust the zero with the solvent, measure the absorbance value of the reagent blank solution for blank correction, and under the same conditions, measure its absorbance value in turn, and draw a calibration curve. At the same time, prepare a sample solution of appropriate concentration, and under the above conditions, measure the absorbance value. According to the measured absorbance value, find the concentration of the element to be measured in the sample solution on the calibration curve (see Figure 1). The concentration of the element to be measured should be within the linear range of the calibration curve.
Micro-measurement of element absorbance
Liquidity of the element to be measured
Standard liquid concentration
Figure 1 Standard curve method calibration curve
This method is only applicable to the determination under the condition of no interference from the matrix. When using the standard curve method, it should be noted that:
Try to eliminate the interference in the sample solution.
The calibration solution and the sample solution matrix should be kept as consistent as possible. h.
If there is interference in the matrix, the standard addition method should be used. c
7.3.2 Standard addition method
GB/T 15337—94
Under the possible conditions of the instrument, take five equal portions of the sample to be tested. One portion is the calibration solution, and the other four portions are added with calibration solutions of different concentrations according to the ratio. The concentrations of the solutions are usually C+c+2c+3cc+4c. Under the specified instrument conditions, the solvent is used to adjust the zero; the absorbance value of the reagent blank solution is measured for blank correction. Under the same conditions, the absorbance values are measured in turn, and the absorbance and concentration calibration curve is drawn with the concentration of the added calibration solution as the horizontal axis and the corresponding absorbance as the vertical axis. The intersection point c of the curve with the concentration axis in the reverse direction is the concentration of the element to be measured in the sample solution, see Figure 2. Accurate calibration
Figure 2 Standard addition method calibration curve
When using the standard addition method, please note:
&. This method is only applicable to the area where concentration and absorbance are linear. b. At least four points (including the sample solution itself) should be used to draw the extrapolation relationship curve. At the same time, the concentration of the first added calibration solution should be roughly the same as the liquid density of the sample solution, that is, c. Generally, the sample solution and the calibration solution are predicted, and the absorbance values of the two are compared for judgment, and then the third and fifth calibration solutions are prepared according to the liquid density of 2c. and 4c, respectively. c. If there is background absorption, the background is deducted by the instrument. If there is no background correction system, the non-absorption line can be used to measure the background absorption alone. When drawing the graph, the material concentration axis moves up a distance, and its size is the absorbance value of the background. 7.3-3 High-precision ratio method
Prepare two calibration solutions, whose concentrations are 5% higher and lower than the sample solution, respectively. According to the determination conditions, aspirate the lower concentration calibration solution, adjust the reading system to make the absorbance value zero or the low reading value + aspirate the higher concentration standard solution, and expand the scale to the maximum reading. Re-aspirate the low concentration calibration solution and readjust to the low reading. According to the software, measure the low concentration calibration solution, sample symptoms and commercial standard, repeat the determination, and obtain three groups of readings. Take the average value of each group of readings and calculate the concentration of the sample solution according to the following proportional formula G
where · c, Ch>c)—
(R, -R)(c G)
is the concentration of the sample solution, high concentration calibration solution and low concentration calibration solution, respectively, Bg/mL: R,, R, R—is the absorbance reading value of the sample solution, high concentration calibration solution and low concentration calibration solution, respectively. This method is only used for high concentration samples that can introduce large interpretation errors using other methods. 7.4 Calculation and expression of the content of the element to be measured + (2)
After determining the concentration of the element to be measured in the sample solution according to 7.3, calculate the content of the element in the sample according to the provisions of the analytical method and express it in terms of mass fraction (%, mg/kg) and mass concentration (mg/L.pg/L) etc. 8 Precision
Determined in accordance with GB 4471.
GB/T15337-94
For the indoor repeatability precision of the same laboratory, the indoor standard deviation and indoor repeatability can be determined by the same person under the same instrument and the same measurement conditions, and the number of measurements is not less than 11 times. 9 Conditions and safety of instrument laboratories
9.1 The conditions of instrument laboratories should meet the following requirements. There should be no strong electromagnetic interference, no corrosive gas, dust or smoke in the room. The room temperature should be between 10 and 35℃: the relative humidity should not exceed 85%; the instrument should not be exposed to direct sunlight and should not be subject to vibration that affects its use; the voltage change of the power supply should not exceed 220V ± 10%, and the frequency change should not exceed (50 ± 1) Hz. 9.2 Safety
Atomic absorption spectrometry often uses high-pressure gas, flammable and explosive gas and harmful gas, etc., and the following matters must be noted. 9.2.1 An exhaust device should be installed above the atomic absorption cell. 9.2.2 The power cord shall not be placed on the heater or radiator. The power supply can only be connected when the circuit connection is confirmed to be correct. The ground wire cannot be shared with other instruments. A dedicated ground wire with good grounding should be used.
9.2.3 The gas source should be at an appropriate distance from the instrument. High-pressure gas cylinders should be placed outdoors as much as possible and should not be exposed to direct sunlight, wind, rain, ice and snow. At the same time, they should be kept below 40°C. To prevent the flammable gas cylinders from carrying static electricity, they should be stacked on insulating materials such as rubber or synthetic resin boards, and the cylinders should be fixed on the pot and bottle rack. The gas is introduced into the instrument through the pipeline. The pipeline should be checked regularly to prevent gas leakage and strictly abide by the relevant operating procedures. 9.2.4 When using acetylene gas cylinders, the pipeline should not be close to heat sources and electrical equipment, and the distance from open flames should generally not be less than 10m. Special pressure reducing valves and backfire preventers must be installed. Prevent tipping and do not use it horizontally. The pressure input to the host shall not exceed 0.15MPa. It is strictly forbidden for pure and pure silver and its products to come into contact with acetylene. When copper alloy must be used, the copper content should be less than 10%. It is strictly forbidden to use up the gas in the bottle; generally, when it is lower than 0.3MPa, the cylinder should be replaced. For instruments with special requirements for acetylene pressure, the cylinder should be replaced in time according to the instructions. For the regulations on the use of acetylene cylinders, please refer to the "Safety Supervision Regulations for Dissolved Acetylene Cylinders of the State Administration of Labor". 9.2.5 Spontaneous combustion or flammable substances shall not be handled near equipment using flammable gases or oxygen, and these substances shall not be released. 9.2.6 When burning and igniting, the combustion-supporting gas should be introduced first, and then the fuel gas. When shutting down, the fuel gas should be stopped first, and then the combustion-supporting gas. In special circumstances, such as sudden power outages, the acetylene valve should be closed immediately to avoid flashback accidents. 9.2.7 When igniting acetylene-nitrous oxide, first ignite the acetylene-air flame. After the flame stabilizes, gradually increase the acetylene flow rate until the flame is yellow and bright, then quickly switch the valve from "air" to "nitrous oxide". The "nitrous oxide" flow rate has been adjusted before ignition. When extinguishing, quickly switch from "nitrous oxide" to "air" to establish the acetylene-air flame and then extinguish it to avoid flashback. 9.2.8 A dedicated burner must be used for acetylene-nitrous oxide flames. It is absolutely forbidden to use acetylene-air flame burners to avoid flashback.
9.2.9 Pipeline for nitrous oxide The system is absolutely oil-free. All pipes and instruments suspected of being contaminated with oil must be degreased and cleaned. For the decompression of nitrous oxide, an antifreeze type pressure reducing valve should be used. 9.2.10 When igniting oxygen-enriched air-acetylene, first ignite the acetylene-air flame, gradually increase the acetylene flow to the required flow, and gradually increase the oxygen flow to the required flame state according to the experimental requirements. When extinguishing, first close the oxygen gas line and then gradually reduce the amount of acetylene until the flame is extinguished to prevent backfire. 9.2.11 For instruments with Zeeman effect background correction, the cooling water should be turned on before ignition. 9.2.12 After the experiment, spray the high-purity water to clean the atomization system for 5 minutes. GB/T 15337—94
Appendix A
Methods for determining the main performance of the instrument
(Quoting JJG694 atomic absorption spectrophotometer) (supplement)
A1 Determination of wavelength indication error and wavelength repeatability According to the specified working current on the hollow cathode lamp, light the mercury lamp. After it stabilizes, under the condition of spectral bandwidth of 0.2nm, select three to five lines from the following mercury and ammonium spectral lines 253.71365.01435.8; 546.1, 640.2, 724.5 and 871.6nm according to the principle of uniform distribution, and make three unidirectional (from short wave to long wave) measurements one by one. The wavelength indication with the maximum energy is taken as the measured value. The wavelength indication error (A) and wavelength repeatability (3) are calculated according to formula (A1) and formula (A2) respectively. A
In the formula, α is the standard value of the wavelength of mercury and nitrogen spectral lines, and A is the measured value of the wavelength of mercury and nitrogen spectral lines. In the formula: —— the maximum value of the three wavelength measurements of a certain spectral line; A in is the minimum value of the three wavelength measurements of a certain spectral line, A2 resolution determination
(A1)
Light up the manganese lamp, wait for it to stabilize, and adjust the photomultiplier tube high voltage when the spectrum bandwidth is 0.2nm, so that the energy of the 279.5nm spectral line is 100. Then scan and measure the manganese double line, and at this time, the 279.5nm should be clearly distinguished. and 279.8 ntm, and the peak-to-valley energy between the two lines should not exceed 40%.
A3 Baseline stability determination
A3.1 Static baseline stability determination
Adjust the spectral bandwidth to 0.2 nm, expand the range by 10 times, light the copper lamp, and measure according to the following steps when the atomization system is not working.
A3.1.1 Single-beam instrument baseline stability determination: After preheating the instrument and the copper lamp for 30 minutes, use the instantaneous measurement method or the time constant is not greater than 0.5 s to measure the stability of the 324.7 Ⅱm spectrum line within 30 minutes, that is, the maximum zero drift and maximum instantaneous noise (peak-to-peak value) within 30 minutes.
A3.1.2 Double-beam instrument baseline stability determination: Preheat the instrument for 30 minutes and the copper lamp for 3 minutes, and then measure the maximum zero source and maximum instantaneous noise (peak-to-peak value) within 30 minutes according to \A3.1. 1\. A3.2 Determination of ignition baseline stability
According to the best conditions for copper measurement, ignite the acetylene-air flame, absorb and spray deionized water, and after 10 minutes, measure the maximum zero drift and maximum instantaneous noise within 30 minutes according to "A3.1" under the condition of absorbing and spraying deionized water. A4 Edge Energy Determination
Ignite the flame and the lamp, and after they are stable, under the conditions of spectral bandwidth of 0.2 nm and response time of no more than 1.5 s (the instrument in use and after repair can use the conditions recommended by the manufacturer), measure the As193.7nm and Cs852.1nm spectral lines according to the following regulations. A4.1 The peak energy of the two spectral lines should be able to be adjusted to 100%, and the background value/value should not be greater than 2%. A4.2 The instantaneous noise of the measured spectral lines, the maximum instantaneous noise (peak value) within 5 minutes should not be greater than 0.03 AlGB/T 15337--94
A4.3 When the two spectral lines are adjusted to 100% energy, the high voltage of the photomultiplier tube shall not exceed 650V. The instrument can be relaxed to 85% of the maximum high voltage value of the instrument during use and after repair.
A5 Determination of detection limit
A5.1 Determination of detection limit [c1(3)] of flame atomic absorption spectrometry A5.1.1. Using copper as the representative element, adjust all parameters of the instrument to the best working state, adjust to zero with the reagent blank solution, and repeat the absorbance (A) of three different concentrations (c) of copper calibration solutions three times. After taking the average value of the three measurements, the slope of the working curve is calculated by linear regression method. It is the sensitivity CS of flame absorption spectroscopy. , A/(μg·mL-1)). S, = dA/dc
（A3)
A5.1.2 Under the same conditions as in \A5.1.1”, expand the scale by 10 times, measure the absorbance of the reagent blank solution (or the solution with a concentration three times the detection limit) 11 times, and calculate its standard deviation: (A, - A)
Standard deviation;
Where. s.
A,——the absorbance value of a single drinking plate; A——the arithmetic mean of the absorbance values measured 11 times, the number of measurements.
A5.1.3 Calculate the detection limit of copper by the instrument according to formula (A5), the unit is μg/mL. r( = 3) = 3SA/S,
A5.2 Graphite furnace atomic absorption harmonic detection limit Q (=3)) determination - (A4)
A5.2.1Use cadmium as the representative element, adjust the instrument parameters to the best working state, use the reagent blank solution to zero, and perform three absorbance measurements of three different concentrations (c) of calibration solutions. After taking the average of the three measurements, the slope of the working curve is calculated by linear regression, which is the sensitivity of graphite furnace atomic absorption spectrometry (SαA/pg). Sα = dA/dQ = dA/d(c V)
Where: c-
Concentration of cadmium calibration solution, ng/mL:
V——sampling volume.μL.
A5.2.2Under the same conditions as in *A5.2.1\, perform 11 soft absorbance measurement on the reagent blank solution and calculate its standard deviation (S). The calculation formula is shown in A5.1.2 (A4). A5.2-3Calculate the detection limit of cadmium by the instrument according to formula (A7), and its unit is Pg. Qi(k = 3) = 35-/S
A6 Determination of characteristic concentration (or characteristic quantity)
The characteristic concentration (cc) of copper measured by flame atomic absorption spectrometry and the characteristic quantity (c, substance) measured by stone fireplace atomic absorption spectrometry can be directly quoted from the results of A5.1.1 and A5.2.1, and calculated according to formula (A8) and formula (A9) respectively. cc
In the formula: S.—Sensitivity of flame atomic absorption spectrometry in A5.1.1, Sc--Sensitivity of graphite furnace atomic absorption spectrometry in A5.2.1, C.
Characteristic concentration of copper measured by flame atomic absorption spectrometry, ug/mL;-(A8)
GB/T15337-94
Characteristic quantity of cadmium measured by graphite furnace atomic absorption spectrometry, P&. A7 Instrument precision measurement
A7.1 Flame atomic absorption spectrophotometric precision measurement: Take thorium as the representative element, when carrying out the measurement in A5.1.1, select the calibration solution with medium concentration, make the absorbance in the range of 0.1~0.3, continue to carry out 7 measurements, and calculate its relative standard deviation, which is the instrument precision of flame atomic absorption spectrometry for copper measurement. A7.2 Graphite furnace atomic absorption spectrometry precision measurement: Take thorium as the representative element, when carrying out the measurement in A5.2.1, continue to carry out 7 repeated measurements of the calibration solution with medium concentration of thorium, and calculate its relative standard deviation, which is the instrument precision of graphite furnace atomic absorption spectrometry for copper measurement.
Appendix B
Non-absorption lines used for background correction
(filler)
Non-absorption lines of the element to be measured
Measured element
Measured element
Resonant absorption wavelength
Table B2 Non-absorption lines of other elements
Co-absorption wavelength
Non-absorption line wavelength
Non-absorption lines of the measured element itself
Non-absorption wavelength
Non-absorption lines of other elements
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