GB/T 11739-1989 Standard method for the examination of lead in the atmosphere of residential areas - Atomic absorption spectrophotometry
Some standard content:
National Standard of the People's Republic of China
Standard method for hygienic examination of lead in air of residentiat areas-Atomic absorption spectrophotometry
Standard method for hygienic examination of lead in air of residentiat areas-Atomic absorption spectrophotometry Subject content and scope of application
This standard specifies the determination of lead concentration in air of residentiat areas by atomic absorption spectrophotometry. This standard is applicable to the determination of lead concentration in total suspended particulate matter and respirable particulate matter in the atmosphere of residential areas. 1.1 Sensitivity
GB 11739-89
The flame atomic absorption method can produce 1% absorption for 0.5μg/mL lead, and the graphite furnace atomic absorption method is 4.1×10～4μg lead. 1.2 The detection limit
The flame atomic absorption method is 0.24μg/mL lead; the graphite furnace atomic absorption method is 6.6×105μg lead. 1.3 Determination range
The lead in total suspended particulate matter uses a large flow sampler. If the gas is collected at a flow rate of 1.1m2/min for 420m2, its measurement range is 5×10-4～7× 103mg/m2, graphite furnace atomic absorption method is 5×10-6～7×10~5mg/m2. For lead in inhalable particulate matter, use an inhalable particulate matter sampler, sample 1.0m2 of gas at the flow rate specified by the sampler, and the graphite furnace atomic absorption method is 5×10-4～7×10-3mg/m2. 1.4 Interference
According to the conditions specified in this method, no interference of other metal elements on the lead determination is found. 2 Principle
The lead and its compounds collected on the glass fiber filter paper are heated with dilute nitric acid and quantitatively transferred to the solution in the form of ions. The 83.3nm lead spectrum line is measured by absorption spectrophotometry. 3 Reagents and materials
3.1 Water: All experimental water is lead-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 2mo1/L. 3. 4 Lead standard solution: Accurately weigh 0.5000g of metallic lead (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. 1.00mL of this solution contains 1000ug lead. Before use, dilute with 0.8mol/L nitric acid solution to 1.00mL containing 100μg and 1.00mL containing 1.0μg lead standard solution. Instruments and equipment
4.1 Large flow sampler: flow range l title 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
GB11739-89
4.2 Inhalable particle sampler: a sampler for collecting airborne particles with a diameter of less than 10μm. Requirements: D product = 10±1μm, g2 = 1.5±0.1, can work continuously and stably for more than 12 hours, and the flow error is less than 5%. Note: 1) D50—median diameter of particles. 2) αg—geometric standard deviation.
Electric constant temperature water bath.
4.4 Glassware III: 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 Lead hollow cathode lamp.
4.6 Original absorption spectrophotometer: attached 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 gas at a flow rate of 1.1~1.7m2/min, 420m2 of gas by flame method, and 10m2 by graphite furnace method.5.2 Sampling of inhalable particulate matter: Place the filter paper flat on the sampling clamp of the inhalable particulate matter sampler and clamp it, and sample 1.0m 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 large gas pressure during sampling.
6 Analysis steps
6.1 Drawing of standard curve
6.1.1 Take 6 50mL volumetric flasks, add lead 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.
100μg/mL standard solution, mL
Lead concentration, μg/mL
1.0μg/mL standard solution, mL
Lead concentration, μg/mL
Flame desorption standard series
Table 2 Graphite furnace method standard series
6.1.2 Adjust the original absorption spectrophotometer to the best working state. Under the working conditions of lead [see Appendix A (reference)], measure the absorbance (or peak height) of each point in the standard series. 6.1.3 Draw a standard curve with the absorbance (or peak height) minus the zero concentration solution as the ordinate and the lead concentration (ug/mL) as the abscissa, and calculate the slope of the curve. The reciprocal of the slope is used as the calculation factor Bs [μg/(mL·absorbance) or 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 determination, take a standard solution with a lead concentration close to the sample for atomic absorption determination, and measure the average absorbance or peak height. Calculate the correction factor by formula (1): f
Where:
f—correction factor, μg/(mL·absorbance) or μg/(mL·mm), cs
—concentration of standard solution, μg/mL,
hs—average peak height of standard solution, absorbance or mmho.
Blank solution peak height, absorbance or mm.
6.2 Sample determination
6.2.1 Sample treatment
Take 50cm2 of total suspended particulate matter sampling filter paper, take 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 20mL2mol/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 use a small amount of water to wash the test tube several times, add the washing liquid to the volumetric flask, and then add water to the scale and mix it. Let it stand for 1h (or centrifuge it), 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 gas sampling volume under standard conditions according to formula (2): Vn=V.-
273 +t
Wherein: V.--the sampling volume converted into standard conditions, L, Vt
-the sampling volume, L;
T.--the absolute temperature under standard conditions, 273K, t--the temperature at the time of sampling, ℃,
po--the atmospheric pressure under standard conditions, 101.3kPa, the atmospheric pressure at the time of sampling, kPa.
7.2 Use the standard curve method to check the standard curve for quantification, or use formula (3) to calculate the lead concentration in the air: 50×(h-ho)×Bs
Lead concentration in air, mg/m3,
Where:
-peak height of sample solution, mm;
peak height of blank solution, mm;
-volume of prepared sample solution, mL,
Calculation factor obtained from 6.1.3, μg/(mL·absorbance) or μg/(mL·mm), S, - same Total filter area of sample filter paper, cm2, S, - filter area of sample filter paper taken during analysis, cm2. 7.3 Calculate the lead concentration in the air using the single-point correction method according to formula (4): C
Where: c
50×(h-hg)×f
lead concentration in the air, mg/m2;
correction factor obtained from 6.1.4, μg/(mL, absorbance) or μg/(mL, mm); average peak height of sample solution, absorbance or mm; - peak height of blank solution, absorbance or mm. (2)
(4)
8 Precision and accuracy
GB11739-89
Repeat the measurement of the filter paper sample after sampling (0.11μg/m2), the coefficient of variation is less than 10%, and the recovery rate of sample (10μg/mL) plus standard (4-20μg/mL) is in the range of 90% to 110%. 154
GB11739-89
Appendix A
Instrument working conditions for the determination of lead by atomic absorption spectrophotometry (reference part)
Because atomic absorption analysis often varies due to different working conditions. Therefore, the best atomic absorption working conditions for analyzing lead should be formulated according to 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 working conditions are shown in Table A1. Table A1
Wavelength, nm
Lamp current, mA
Slit, nm
Burner height, mmbzxZ.net
Acetylene gas flow, L/min
Air flow, L/min
A2See Table A2 for the working conditions of graphite furnace atomic absorption spectrometry instrument. Table A2
Wavelength, nm
Lamp current, mA
Slit, nm
Drying current, A
Time, s
Current, A
Time, s
Atomization current, A
Time, s
Injection volume, μL
Additional notes:
This standard is proposed by the Department of Health Supervision, Ministry of Health. 283.3
This standard was drafted by Shenyang Municipal Health and Epidemic Prevention Station, Shanghai Municipal Health and Epidemic Prevention Station, Shandong Provincial Environmental Health Monitoring Station, Liaoning Provincial Health and Epidemic Prevention Station, and School of Public Health of 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 Environmental Health Monitoring Institute of the Chinese Academy of Preventive Medicine, the technical unit entrusted by the Ministry of Health. 155
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