GB/T 11740-1989 Standard method for sanitation examination of cadmium in the atmosphere of residential areas - Atomic absorption spectrophotometry
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National Standard of the People's Republic of China
Standard method for hygienic examination of cadmium in air of residential areas - Atomic absorption spectrophotometry
Standard method for hygienic examination of cadmium in air of residential areas - Atomic absorption spectrophotometry 1 Subject content and scope of application
This standard specifies the determination of cadmium concentration in air of residential areas by atomic absorption spectrophotometry. This standard applies to the determination of cadmium concentration in total suspended particulate matter and inhalable particulate matter in the atmosphere of residential areas. 1.1 Sensitivity
GB11740-89
The flame atomic absorption method can produce 1% absorption for 0.023μg/mL cadmium, and the graphite furnace atomic absorption method is 3.9×10-'μg cadmium. 1.2 Detection limit
The flame atomic absorption method is 0.017μg/mL cadmium, and the graphite furnace atomic absorption method is 5.5×10-'μg cadmium. 1.3 Determination range
For total suspended particulate matter, if a large flow sampler is used and 60m2 of gas is sampled at a flow rate of 1.1m2/min, the measurement range is: 2.4×10-4~4.8×10~3mg/m for air-acetylene flame atomic absorption method and 3.5×10-6~4.8×10-5mg/m for graphite furnace atomic absorption method. For cadmium in inhalable particulate matter, use an inhalable particulate matter sampler and sample 0.5m3 of gas at the flow rate specified by the sampler. The measurement range of graphite furnace atomic absorption method is 1×10-4~1.4×10-3mg/m3.1.4 Interference
According to the conditions specified in this method, no other metal elements interfere with the determination of cadmium. 2 Principle
Cadmium and its compounds collected on glass fiber filter paper are leached by heating with dilute nitric acid, quantitatively transferred to the solution in the form of ions, and determined by atomic absorption spectrophotometry at the 228.8nm pan spectrum. 3 Reagents and materials
3.1 Water: All experimental water is cadmium-free deionized water. 3.2 Glass fiber filter paper (hereinafter referred to as filter paper): When used for large-flow samplers to collect total suspended particulate matter, the filter paper is "49" type, with a specification of 200mm×250mm. When used for inhalable particulate matter samplers to collect inhalable particulate matter, the filter paper diameter is determined by the sampler used. 3.3 Nitric acid: Use high-grade pure nitric acid and water to prepare solutions with concentrations of 1+1, 0.8mol/L, and 2mol/L. 3.4 Cadmium standard solution: Accurately weigh 0.5000g of metallic cadmium (99.99%) in a 150mL beaker, add 20mL (1+1) nitric acid, heat to dissolve, remove and cool, transfer to a 500mL volumetric flask, dilute to scale with water, and mix. This solution contains 1000μg cadmium in 1.00mL. Before use, dilute with 0.8mol/L nitric acid solution to 1.00mL containing 10μg and 1.00mL containing 0.1μg cadmium standard solution. 4 Instruments and equipment
4.1 Large flow sampler: flow range 1.1~1.7m2/min. The filter paper specification is 200mm×250mm, and the particle diameter that can be collected is 0.1~100μm. And it can continuously and stably sample for more than 24h. Approved by the Ministry of Health of the People's Republic of China on September 21, 1989 and implemented on July 1, 1990
GB 11740-89
4.2 Inhalable particle sampler: a sampler for collecting particles in the air with a diameter of less than 10μm. Population requirements: D=10±1μm, u2=1.5±0.1, can work continuously and stably for more than 12 hours, and the flow error is less than 5%. Note: 1) Ds0--median diameter of particles. 2) Geometric standard deviation.
4.3 Electric constant temperature water bath.
4.4 Glassware: The glassware such as volumetric flasks and test tubes used must be soaked and cleaned with 10% nitric acid and rinsed with deionized water. 4.5 Hollow cathode lamp.
4.6 Atomic absorption spectrophotometer: with graphite furnace. 5 Sampling
5.1 Sampling of total suspended particulate matter: Place 200mm×250mm filter paper flat on the sampling clamp of the large flow sampler and clamp it. Sample steam at a flow rate of 1.1~1.7m2/min, 60m2 of steam by flame method, and 10m2 of gas by graphite furnace method.5.2 Sampling of inhalable particulate matter: Place the filter paper flat on the sampling clamp of the sampler for inhalable particulate matter and clamp it, and sample 0.5m2 at the flow rate specified by the sampler.
After sampling, carefully remove the sampling filter paper, fold it in half with the dust side inward, put it in a clean paper bag, and then put it in the sample box for storage. Record the temperature and maximum pressure during sampling.
6 Analysis steps
6.1 Drawing of standard curve
6.1.1 Take 6 50mL volumetric flasks, add cadmium standard solution according to Table 1 or Table 2, dilute to the scale with 0.8mol/L nitric acid solution, and prepare the standard series.
Table 1 Flame method standard series
10 μg/mL standard solution, mL
Pot concentration, μg/mL
0.1 μg/mL standard solution, mL
Pot concentration, μg/mL
Graphite furnace method standard series
6.1.2 Adjust the atomic absorption spectrophotometer to the best working state, and measure the absorbance (or peak height) of each point in the standard series under the working conditions of cadmium [see Appendix A (reference)]. 6.1.3 Use the absorbance (or peak height) minus the zero concentration solution as the ordinate and the cadmium concentration (μg/mL) as the abscissa to draw the standard curve, and calculate the slope of the regression line, and use the inverse of the slope as the calculation factor Bs [μg/(mL·mm)]. 6.1.4 When the instrument stability is poor, the single-point calibration method can be used to calculate the correction factor: At the same time as the sample is measured, take a standard solution with a cadmium concentration close to the sample for atomic absorption measurement, and measure the average absorbance or peak height. Calculate the correction factor by formula (1): f =
correction factor, μg/(mL·absorbance) or μg/(mLmm) Where: f
-standard solution concentration, μg/mL!
h-average peak height of the standard solution, absorbance or mmh. -blank solution peak height, absorbance or mm. 6.2 Sample determination
6.2.1 Sample treatment
·(1)
Take 50cm2 of total suspended particulate matter sampling filter paper and half of the inhalable particulate matter sampling filter paper (inhalable particulate matter must be determined by graphite furnace method), place the sample in a 50mL graduated test tube, add 20mL 2mol/L nitric acid solution to immerse the sample, heat it in a boiling water bath in a fume hood for 1h, take it out and cool it to room temperature, transfer it to a 50mL volumetric flask, and wash the test tube several times with a small amount of water, add the washing solution to the volumetric flask, add water to the scale, and mix well. Let it stand for 1h (or centrifuge it), and take the supernatant for determination. At the same time, use the unsampled filter paper to prepare a blank solution according to the operating steps for preparing the sample solution. 6.2.2 While drawing the standard curve, measure the absorbance (or peak height) of the sample and blank solution. 7 Calculation of results
7.1 Convert the sampling volume into the sampling volume under standard conditions according to formula (2): Vo=V.
Wherein, V. -
273 +t
-sampling volume converted into the sampling volume under standard conditions, L, Vt
-sampling volume, L
T. —absolute temperature under standard conditions, 273 K, t—temperature at the time of sampling, °C,
po—atmospheric pressure under standard conditions, 101.3 kPa, b
-atmospheric pressure at the time of sampling, kPa.
7.2 Standard curve method Calculate the concentration of cadmium in the air using formula (3): c=
Cadmium concentration in the air, mg/m3,
Wherein,
50×(h-ho)×Bsx
-peak height of sample solution, absorbance or mm, peak height of blank solution, absorbance or mm
-volume of prepared sample solution, mL,
Calculation factor obtained from 6.1.3, μg/(mL absorbance) or μg/(mL·mm)Total filtration area of sample filter paper, cm2,
S2——filtration area of sample filter paper taken during analysis, cm2. 7.3 Calculate the concentration of cadmium in the air using formula (4) using the single-point correction method: c= 50×(h-ho)×fx
Wherein: cCadmium concentration in the air, mg/m3
From 6.1.4 The obtained correction factor, μg/(mL·absorbance) or μg/(mL·mm), h--peak height of sample solution, absorbance or mm, h.--peak height of blank solution, absorbance or mm. (2
(3)
(4)
Precision and accuracy
GB11740
The filter paper sample (0.04μg/m) after sampling was repeatedly measured, and the coefficient of variation was less than 10%. The recovery rate of sample (0.36μg/mL) plus standard (0.4～1.6μg/mL) was in the range of 90%～110%. 526
GB 11740—89
Appendix A
Instrumental working conditions for the determination of cadmium by atomic absorption spectrophotometry (reference)
Atomic absorption analysis often varies due to different working conditions. Therefore, the optimal atomic absorption working conditions for the analysis should be formulated based on the model and performance of the atomic absorption spectrophotometer. The atomic absorption working conditions listed below are only an example. A1 Flame atomic absorption instrument operating conditions are shown in Table A1. Table A1
Wavelength, nmbzxz.net
Lamp current, mA
Slit, nm
Burner height, mm
Acetylene gas flow, L/min
Air flow, L/min
A2 Graphite furnace atomic absorption instrument operating conditions are shown in Table A2. Table A2
Wavelength, nm
Lamp current, mA
Slit, nm
Burner height, mm
Acetylene gas flow, L/min
Air flow, L/min
A2 Graphite furnace atomic absorption instrument operating conditions are shown in Table A2. Table A2
Wavelength, nm
Lamp current, mA
Slit, nm
Burner height, mm
Acetylene gas flow, L/min
Air flow, L/min
Length, nm
Lamp current, mA
Slit, nm
Current, A
Time, s
Current, A
Time, s
Current, A
Atomic flower
Time, s
Injection volume, μL
Additional remarks:
This standard was proposed by the Department of Health Supervision, Ministry of Health. 228.8
This standard was drafted by Shenyang Municipal Health and Epidemic Prevention Station, Shanghai Municipal Health and Epidemic Prevention Station, Shandong Provincial Environmental Sanitation Monitoring Station, Liaoning Provincial Health and Epidemic Prevention Station, and School of Public Health, Beijing Medical University. The main drafters of this standard are Gao Guichun, Zhang Genfa, Liu Xuejin, Jia Wei, and Li Wei. This standard is interpreted by the Institute of Environmental Sanitation Monitoring, Chinese Academy of Preventive Medicine, the technical unit entrusted by the Ministry of Health. 527
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