Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by China Petroleum and Chemical Industry Association.
This standard is under the jurisdiction of SAC/TC 134/SC 1 the Subcommittee on Textile Auxiliaries of National Technical Committee on Dyestuffs of the Standardization Administration of China.
Determination of 9 heavy metal contents in textile dyeing and finishing auxiliaries
Warning: Persons using this standard shall be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
1 Scope
This standard specifies the method for determining the content of 9 heavy metals in textile dyeing and finishing auxiliaries, including arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), antimony (Sb) and mercury (Hg).
This standard is applicable to the determination of the 9 heavy metal contents in various textile dyeing and finishing auxiliaries.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
3 Determination of 8 heavy metal contents through inductively coupled plasma atomic emission spectrometry
3.1 Theory
After the sample is digested by acid, the emission intensity of 8 heavy metal elements, i.e., lead, cadmium, arsenic, copper, cobalt, nickel, chromium and antimony, in the digestion solution shall be determined by using an inductively coupled plasma atomic emission spectrometer at the corresponding analysis wavelength, the concentration of each heavy metal element shall be determined according to the standard working curve, and the total amount of digested heavy metals in the sample shall be calculated.
3.2 Reagents and materials
Unless otherwise specified, only guaranteed reagents and Grade I water (specified in GB/T 6682) shall be used.
3.2.1 Nitric acid: 65%~68% (mass fraction).
3.2.2 Hydrogen peroxide: 30% (mass fraction).
3.2.3 Fluoboric acid: 49.5%~50.5% (mass fraction).
3.2.4 Sodium hydroxide solution: 100 g/L.
3.2.5 Nitric acid solution (1+9): measure 100 mL of nitric acid (3.2.1) and slowly pure it into 900mL of water, mix well.
3.2.6 Hydrochloric acid solution: 10% (mass fraction).
3.2.7 Single element standard stock solution
The standard stock solution of each element may be prepared using standard substances or according to the following methods:
a) Arsenic (As) standard stock solution (100 μg/mL): weigh 0.132 g of arsenic trioxide which has been dried to constant weight in a sulfuric acid dryer, warm and dissolve it in 1.2 mL of sodium hydroxide solution (3.2.4), then transfer the obtained solution into a 1,000-mL volumetric flask and dilute to the scale.
b) Cadmium (Cd) standard stock solution (100 μg/mL): weigh 0.203g of cadmium chloride (CdCl2·5/2 H2O), dissolve in water, transfer into a 1,000-ml volumetric flask, and dilute to scale.
c) Cobalt (co) standard stock solution (100 μg/mL): weigh 0.263 g of anhydrous cobalt sulfate [igniting the cobalt sulfate (CoSO4·7H2O) at 500℃～550℃ to constant weight], add 150 mL of water, heat to dissolve, cool, transfer to a 1,000-mL volumetric flask, and dilute to scale.
d) Chromium standard stock solution (100 μg/mL): weigh 0.283g of potassium dichromate (K2Cr2O7) in water, then transfer the obtained solution into a 1,000-mL volumetric flask, and dilute to the scale.
e) Copper (Cu) standard stock solution (100 μg/mL): weigh 0.393 g of cupric sulfate (CuSO4·5 H2O), dissolve it in water, transfer into a 1,000-mL volumetric flask, and dilute to the scale.
f) Nickel (Ni) standard stock solution (100 μg/mL): weigh 0.448 g of nickel sulphate (NiSO4·6H2O), dissolve it in water, transfer into a1,000-mL volumetric flask, and dilute to the scale.
g) Lead (Pb) standard stock solution (100 μg/mL): weigh 0.160 g of lead nitrate [Pb(NO3)2], dissolve with 10mL of nitric acid solution (3.2.5), transfer the solution into a 1,000-mL volumetric flask, and dilute to the scale.
h) Antimony (Sb) standard stock solution (100 μg/mL): weigh 0.274 g of antimony potassium tartrate (C4H4KO7Sb·1/2H2O), dissolve in 10% hydrochloric acid solution (3.2.6), transfer into a 1,000-mL volumetric flask, and dilute to scale with 10% hydrochloric acid solution (3.2.6).
Note: Standard stock solution shall be stored in polyester plastic bottles at 0℃～4℃ and kept at dark place, with the validity period being 6 months.
3.3 Apparatus
3.3.1 Microwave digestion instrument.
3.3.2 Inductively coupled plasma emission spectrometer (ICP-AES).
3.3.3 Analytical balance: with a sensibility of 0.1 mg.
3.3.4 Volumetric flasks: 25mL, 100mL and 1,000mL.
3.3.5 Filtering membrane: 0.45μm, water film.
3.3.6 Disposable syringe: 5mL.
3.3.7 Pipette.
3.4 Analytical procedures
3.4.1 Specimen treatment
Accurately weigh 0.200 g～0.250 g of specimen (accurate to 0.001 g) and place in a digestion vessel, add 4 mL of nitric acid (3.2.1), 2 mL of hydrogen peroxide (3.2.2) and 2 mL of fluoboric acid (3.2.3), subject it to microwave digestion at (195±5) ℃ for 20 min, transfer the digestion solution to a 25 mL volumetric flask (3.3.4) and dilute to scale with water, and measure with an inductively coupled plasma emission spectrometer (3.3.2) after being filtered with the water film (3.3.2).
Note: Digestion time and temperature may be slightly adjusted according to apparatus type and model.
3.4.2 Analysis method
3.4.2.1 ICP-AES analysis conditions
As the test result depends on the apparatus adopted, it is impossible to give general parameters for the chromatographic analysis. It has been proved to be suitable for testing to adopt the parameters in Table 1. See Annex A for the wavelengths selected for each element during the test.
Table 1 ICP-AES apparatus working conditions
Power 1.2 kW Apparatus stability delay 15 s
Plasma gas flow 15 L/min Injection delay 30 s
Auxiliary air flow 1.5 L/min Pump speed 15 r/min
Atomization gas flow 0.75 L/min Cleaning time 20 s
3.4.2.2 Preparation of single element series working solution
Respectively transfer 0.3 mL, 0.5 mL, 0.8 mL, 1.0 mL, 3.0 mL, 5.0 mL and 15.0 mL of standard stock solutions (100 μg/mL) (3.2.7) to a 100-mL volumetric flask (3.3.4) with a pipette (3.3.7), then add 3 mL of nitric acid (3.2.1) to them respectively, dilute them to scale with water and prepare them to single element series working solutions with the concentration of 0.3 μg/mL, 0.5 μg/mL, 0.8 μg/mL, 1.0 μg/mL, 3.0 μg/mL, 5.0 μg/mL and 15.0 μg/mL respectively.
Notes:
1 Put the working solutions in a dark place and keep them in polyester plastic bottles at 0 ° C ~ 4 ° C, with the validity period being 3 months.
2 Preparation of mixed series working solutions: Respectively transfer appropriate single element standard storage solutions (3.2.7) to the 100-mL volumetric flask (3.3.4) (with 3 mL of nitric acid (3.2.1)) as needed, then dilute them to scale with water to prepare them to mixed series working solutions.
3.4.2.3 Determination with apparatus
Under corresponding analysis conditions (3.4.2.1), measure the spectral intensities of the to-be-measured elements in the series working solutions (3.4.2.2) in the ascending order of concentration, and then draw a standard working curve with the spectral intensity as the ordinate and the element concentration as the abscissa. Under the same conditions, measure the spectral intensities of the to-be-measured elements in the sample solutions (3.4.1), and then calculate the concentration of them based on the standard working curve.
3.5 Blank test
Conduct the blank test in accordance with the test procedures specified in 3.4.1 and 3.4.2, except that no specimen is added.
3.6 Result calculation
Represented by X and expressed in mg/kg, the content of heavy metal elements in the specimen shall be calculated using Formula (1):
(1)
where,
C1——the concentration of heavy metal elements in the digestion solution, μg/mL;
C0——the concentration of heavy metal elements in the blank solution, μg/mL;
V——the volume of solution, mL;
m——the weighed specimen mass, g;
F——the dilution ratio of solution.
Take the arithmetic average of the parallel measurement results as the result, which shall be rounded to one digit after decimal point according to those specified in GB/T 8170.
3.7 Lower determination limit and precision
3.7.1 Lower determination limit
Lower determination limit of this method is shown in Table 2.
Table 2 Lower determination limit of 8 elements with ICP-AES method
Element Arsenic (As) Cadmium (Cd) Cobalt (Co) Chromium (Cr) Copper (Cu) Nickel (Ni) Lead (Pb) Antimony (Sb)
Limit of detection
mg/kg 2.6 4.8 3.0 4.6 6.9 4.5 9.7 4.7
3.7.2 Precision
The absolute difference between two independent test results obtained from two independent tests performed by the same operator to the same object with the same equipment and test method in the same laboratory during a short time shall not exceed 10% of the arithmetic mean of the two measured values, providing that the cases with test results exceeding 10% of the arithmetic mean of the two measured values do not exceed 5%.
4 Determination of the content of arsenic and mercury with atomic fluorescence spectrophotometry
4.1 Theory
4.1.1 Determination of arsenic content
After digesting the specimen with acid, add the thiourea-ascorbic acid into it to convert the pentavalent arsenic into trivalent arsenic, and then add sodium borohydride into it and reduce it to arsine, which is then carried into the atomizer by the carrier gas and decomposed into atomic arsenic at high temperature. Determine the content of arsenic against the standard working curve at a fluorescence wavelength of 193.7 nm.
4.1.2 Determination of mercury content
After digesting the specimen with acid, add the sodium borohydride into it and reduce the ionic mercury to atomic mercury, which is then carried into the atomizer by the carrier gas. Determine the content of mercury against the standard working curve at a fluorescence wavelength of 253.7 nm.
4.2 Reagents and materials
Unless otherwise specified, only guaranteed reagents and Grade I water (specified in GB/T 6682) shall be used.
4.2.1 Sodium hydroxide.
4.2.2 Nitric acid: same as 3.2.1.
4.2.3 Hydrogen peroxide: same as 3.2.2.
4.2.4 Fluoroboric acid: same as 3.2.3.
4.2.5 Thiourea.
4.2.6 Ascorbic acid.
4.2.7 Sodium hydroxide solution, 100 g/L: same as 3.2.4.
4.2.8 Nitric acid solution (3+47): Take 60 mL of nitric acid (4.2.2) and pour it slowly into 940 mL of water, then mix them well.
4.2.9 Sodium borohydride solution, 10 g/L: Weigh 0.5 g of sodium hydroxide and dissolve it with water, then add 10.0 g of sodium borohydride into it, after the sodium borohydride is dissolved, add water into it and dilute it to 1,000 mL. The solution shall be used on the day it prepared.
4.2.10 Sodium borohydride solution, 0.1 g/L: Weigh 2.0 g of sodium hydroxide and dissolve it with water, after that, add 0.1 g of sodium borohydride into it, after the sodium borohydride is dissolved, add water into it and dilute it to 1,000 mL. The solution shall be used on the day it prepared.
4.2.11 Thiourea-ascorbic acid mixture: Weigh 5.0 g of thiourea and 5.0 g of ascorbic acid respectively and dissolve them with water, after that, add 10 mL of nitric acid (4.2.2) into it, then add water into it and dilute it to 1,000 mL. The solution shall be prepared immediately before use.
4.2.12 Standard stock solution
Standard stock solutions may be prepared with standard substances or prepared according to the following method:
a) Arsenic standard stock solution, 100 mg/L: Accurately weigh 0.1320 g of arsenic trioxide (As2O3) (has been dried to a constant weight in a desiccator) and dissolve it with 10 mL of sodium hydroxide solution (4.2.7), and then transfer it to a 1,000-mL volumetric flask with an appropriate amount of water, then add 60 mL of nitric acid solution (4.2.8) into it and dilute it to scale with water, then mix it well.
b) Mercury standard stock solution, 100mg/L: Accurately weigh 0.135 4 g of dried mercury bichloride (HgCl2) and dissolve it with 60mL of nitric acid solution (4.2.8), after that, transfer it into a 1,000-mL volumetric flask and dilute it to scale with water, then mix it well.
Note: Unless otherwise specified, the standard stock solutions shall have a storage life of 6 months at a low temperature of 0℃ ~ 4℃. In case of turbidity, precipitation or color change, it shall be prepared again.
4.2.13 Standard working solution
4.2.13.1 Arsenic standard working solution, 100 μg/L: Pipet 1.00 mL of arsenic standard stock solution (4.2.12.1) and put it into a 100-mL volumetric flask, then dilute it to scale with water and shake it well to obtain the arsenic standard solution with a concentration of 1 mg/L. Then pipet 10.00 mL of standard solution (1 mg/L) and put it into a 100-mL volumetric flask, then dilute it to scale with water. The solution shall be used on the day it prepared.
4.2.13.2 Mercury standard working solution, 5.0 μg/L: Pipet 5.00mL of mercury standard stock solution (4.2.12.2) and put it into a 100-mL volumetric flask, then dilute it to scale with water and shake it well to obtain the mercury standard solution with a concentration of 5 mg/L. Then pipet 0.10 mL of standard solution (5 mg/L) and put it into a 100-mL volumetric flask (with a small amount of water), then add 6 mL of nitric acid (4.2.2) into it and dilute it to scale with water. The solution shall be used on the day it prepared.
4.3 Apparatus
4.3.1 Atomic fluorescence spectrophotometer: prepare sequential injection sampling device.
4.3.2 Hollow cathode lamp: arsenic lamp and mercury lamp.
4.3.3 Microwave digestion instrument.
4.3.4 Analytical balance: with a sensitivity of 0.1 mg.
4.3.5 Volumetric flask: 10mL, 25mL, 100mL and 1,000mL.
4.3.6 Filter membrane: same as 3.3.5.
4.3.7 Disposable syringe: same as 3.3.6.
4.3.8 Pipette: same as 3.3.7.
4.4 Analytical procedures
4.4.1 Specimen treatment
Weigh 0.200 g～0.250 g of specimen (accurate to 0.001 g), and place it into a microwave digestion tube, then add 3 mL of nitric acid (4.2.2), 2 mL of hydrogen peroxide (4.2.3) and 2 mL of fluoboric acid (4.2.4). After the safety valve is covered, place the digestion tube in a microwave digestion system (4.3.3), and keep it at (195±5) ℃ for 20 min. After digestion, transfer the solution to a 25-mL volumetric flask (4.3.5) and dilute it to scale with water after the solution is cooled to room temperature, and filter it with the water film (4.3.6) for later use.
Foreword i
1 Scope
2 Normative references
3 Determination of 8 heavy metal contents through inductively coupled plasma atomic emission spectrometry
4 Determination of the content of arsenic and mercury with atomic fluorescence spectrophotometry
5 Test report
Annex A (Informative) Selected wavelengths for element determination with ICP-AES method
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by China Petroleum and Chemical Industry Association.
This standard is under the jurisdiction of SAC/TC 134/SC 1 the Subcommittee on Textile Auxiliaries of National Technical Committee on Dyestuffs of the Standardization Administration of China.
Determination of 9 heavy metal contents in textile dyeing and finishing auxiliaries
Warning: Persons using this standard shall be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
1 Scope
This standard specifies the method for determining the content of 9 heavy metals in textile dyeing and finishing auxiliaries, including arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), antimony (Sb) and mercury (Hg).
This standard is applicable to the determination of the 9 heavy metal contents in various textile dyeing and finishing auxiliaries.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
3 Determination of 8 heavy metal contents through inductively coupled plasma atomic emission spectrometry
3.1 Theory
After the sample is digested by acid, the emission intensity of 8 heavy metal elements, i.e., lead, cadmium, arsenic, copper, cobalt, nickel, chromium and antimony, in the digestion solution shall be determined by using an inductively coupled plasma atomic emission spectrometer at the corresponding analysis wavelength, the concentration of each heavy metal element shall be determined according to the standard working curve, and the total amount of digested heavy metals in the sample shall be calculated.
3.2 Reagents and materials
Unless otherwise specified, only guaranteed reagents and Grade I water (specified in GB/T 6682) shall be used.
3.2.1 Nitric acid: 65%~68% (mass fraction).
3.2.2 Hydrogen peroxide: 30% (mass fraction).
3.2.3 Fluoboric acid: 49.5%~50.5% (mass fraction).
3.2.4 Sodium hydroxide solution: 100 g/L.
3.2.5 Nitric acid solution (1+9): measure 100 mL of nitric acid (3.2.1) and slowly pure it into 900mL of water, mix well.
3.2.6 Hydrochloric acid solution: 10% (mass fraction).
3.2.7 Single element standard stock solution
The standard stock solution of each element may be prepared using standard substances or according to the following methods:
a) Arsenic (As) standard stock solution (100 μg/mL): weigh 0.132 g of arsenic trioxide which has been dried to constant weight in a sulfuric acid dryer, warm and dissolve it in 1.2 mL of sodium hydroxide solution (3.2.4), then transfer the obtained solution into a 1,000-mL volumetric flask and dilute to the scale.
b) Cadmium (Cd) standard stock solution (100 μg/mL): weigh 0.203g of cadmium chloride (CdCl2·5/2 H2O), dissolve in water, transfer into a 1,000-ml volumetric flask, and dilute to scale.
c) Cobalt (co) standard stock solution (100 μg/mL): weigh 0.263 g of anhydrous cobalt sulfate [igniting the cobalt sulfate (CoSO4·7H2O) at 500℃～550℃ to constant weight], add 150 mL of water, heat to dissolve, cool, transfer to a 1,000-mL volumetric flask, and dilute to scale.
d) Chromium standard stock solution (100 μg/mL): weigh 0.283g of potassium dichromate (K2Cr2O7) in water, then transfer the obtained solution into a 1,000-mL volumetric flask, and dilute to the scale.
e) Copper (Cu) standard stock solution (100 μg/mL): weigh 0.393 g of cupric sulfate (CuSO4·5 H2O), dissolve it in water, transfer into a 1,000-mL volumetric flask, and dilute to the scale.
f) Nickel (Ni) standard stock solution (100 μg/mL): weigh 0.448 g of nickel sulphate (NiSO4·6H2O), dissolve it in water, transfer into a1,000-mL volumetric flask, and dilute to the scale.
g) Lead (Pb) standard stock solution (100 μg/mL): weigh 0.160 g of lead nitrate [Pb(NO3)2], dissolve with 10mL of nitric acid solution (3.2.5), transfer the solution into a 1,000-mL volumetric flask, and dilute to the scale.
h) Antimony (Sb) standard stock solution (100 μg/mL): weigh 0.274 g of antimony potassium tartrate (C4H4KO7Sb·1/2H2O), dissolve in 10% hydrochloric acid solution (3.2.6), transfer into a 1,000-mL volumetric flask, and dilute to scale with 10% hydrochloric acid solution (3.2.6).
Note: Standard stock solution shall be stored in polyester plastic bottles at 0℃～4℃ and kept at dark place, with the validity period being 6 months.
3.3 Apparatus
3.3.1 Microwave digestion instrument.
3.3.2 Inductively coupled plasma emission spectrometer (ICP-AES).
3.3.3 Analytical balance: with a sensibility of 0.1 mg.
3.3.4 Volumetric flasks: 25mL, 100mL and 1,000mL.
3.3.5 Filtering membrane: 0.45μm, water film.
3.3.6 Disposable syringe: 5mL.
3.3.7 Pipette.
3.4 Analytical procedures
3.4.1 Specimen treatment
Accurately weigh 0.200 g～0.250 g of specimen (accurate to 0.001 g) and place in a digestion vessel, add 4 mL of nitric acid (3.2.1), 2 mL of hydrogen peroxide (3.2.2) and 2 mL of fluoboric acid (3.2.3), subject it to microwave digestion at (195±5) ℃ for 20 min, transfer the digestion solution to a 25 mL volumetric flask (3.3.4) and dilute to scale with water, and measure with an inductively coupled plasma emission spectrometer (3.3.2) after being filtered with the water film (3.3.2).
Note: Digestion time and temperature may be slightly adjusted according to apparatus type and model.
3.4.2 Analysis method
3.4.2.1 ICP-AES analysis conditions
As the test result depends on the apparatus adopted, it is impossible to give general parameters for the chromatographic analysis. It has been proved to be suitable for testing to adopt the parameters in Table 1. See Annex A for the wavelengths selected for each element during the test.
Table 1 ICP-AES apparatus working conditions
Power 1.2 kW Apparatus stability delay 15 s
Plasma gas flow 15 L/min Injection delay 30 s
Auxiliary air flow 1.5 L/min Pump speed 15 r/min
Atomization gas flow 0.75 L/min Cleaning time 20 s
3.4.2.2 Preparation of single element series working solution
Respectively transfer 0.3 mL, 0.5 mL, 0.8 mL, 1.0 mL, 3.0 mL, 5.0 mL and 15.0 mL of standard stock solutions (100 μg/mL) (3.2.7) to a 100-mL volumetric flask (3.3.4) with a pipette (3.3.7), then add 3 mL of nitric acid (3.2.1) to them respectively, dilute them to scale with water and prepare them to single element series working solutions with the concentration of 0.3 μg/mL, 0.5 μg/mL, 0.8 μg/mL, 1.0 μg/mL, 3.0 μg/mL, 5.0 μg/mL and 15.0 μg/mL respectively.
Notes:
1 Put the working solutions in a dark place and keep them in polyester plastic bottles at 0 ° C ~ 4 ° C, with the validity period being 3 months.
2 Preparation of mixed series working solutions: Respectively transfer appropriate single element standard storage solutions (3.2.7) to the 100-mL volumetric flask (3.3.4) (with 3 mL of nitric acid (3.2.1)) as needed, then dilute them to scale with water to prepare them to mixed series working solutions.
3.4.2.3 Determination with apparatus
Under corresponding analysis conditions (3.4.2.1), measure the spectral intensities of the to-be-measured elements in the series working solutions (3.4.2.2) in the ascending order of concentration, and then draw a standard working curve with the spectral intensity as the ordinate and the element concentration as the abscissa. Under the same conditions, measure the spectral intensities of the to-be-measured elements in the sample solutions (3.4.1), and then calculate the concentration of them based on the standard working curve.
3.5 Blank test
Conduct the blank test in accordance with the test procedures specified in 3.4.1 and 3.4.2, except that no specimen is added.
3.6 Result calculation
Represented by X and expressed in mg/kg, the content of heavy metal elements in the specimen shall be calculated using Formula (1):
(1)
where,
C1——the concentration of heavy metal elements in the digestion solution, μg/mL;
C0——the concentration of heavy metal elements in the blank solution, μg/mL;
V——the volume of solution, mL;
m——the weighed specimen mass, g;
F——the dilution ratio of solution.
Take the arithmetic average of the parallel measurement results as the result, which shall be rounded to one digit after decimal point according to those specified in GB/T 8170.
3.7 Lower determination limit and precision
3.7.1 Lower determination limit
Lower determination limit of this method is shown in Table 2.
Table 2 Lower determination limit of 8 elements with ICP-AES method
Element Arsenic (As) Cadmium (Cd) Cobalt (Co) Chromium (Cr) Copper (Cu) Nickel (Ni) Lead (Pb) Antimony (Sb)
Limit of detection
mg/kg 2.6 4.8 3.0 4.6 6.9 4.5 9.7 4.7
3.7.2 Precision
The absolute difference between two independent test results obtained from two independent tests performed by the same operator to the same object with the same equipment and test method in the same laboratory during a short time shall not exceed 10% of the arithmetic mean of the two measured values, providing that the cases with test results exceeding 10% of the arithmetic mean of the two measured values do not exceed 5%.
4 Determination of the content of arsenic and mercury with atomic fluorescence spectrophotometry
4.1 Theory
4.1.1 Determination of arsenic content
After digesting the specimen with acid, add the thiourea-ascorbic acid into it to convert the pentavalent arsenic into trivalent arsenic, and then add sodium borohydride into it and reduce it to arsine, which is then carried into the atomizer by the carrier gas and decomposed into atomic arsenic at high temperature. Determine the content of arsenic against the standard working curve at a fluorescence wavelength of 193.7 nm.
4.1.2 Determination of mercury content
After digesting the specimen with acid, add the sodium borohydride into it and reduce the ionic mercury to atomic mercury, which is then carried into the atomizer by the carrier gas. Determine the content of mercury against the standard working curve at a fluorescence wavelength of 253.7 nm.
4.2 Reagents and materials
Unless otherwise specified, only guaranteed reagents and Grade I water (specified in GB/T 6682) shall be used.
4.2.1 Sodium hydroxide.
4.2.2 Nitric acid: same as 3.2.1.
4.2.3 Hydrogen peroxide: same as 3.2.2.
4.2.4 Fluoroboric acid: same as 3.2.3.
4.2.5 Thiourea.
4.2.6 Ascorbic acid.
4.2.7 Sodium hydroxide solution, 100 g/L: same as 3.2.4.
4.2.8 Nitric acid solution (3+47): Take 60 mL of nitric acid (4.2.2) and pour it slowly into 940 mL of water, then mix them well.
4.2.9 Sodium borohydride solution, 10 g/L: Weigh 0.5 g of sodium hydroxide and dissolve it with water, then add 10.0 g of sodium borohydride into it, after the sodium borohydride is dissolved, add water into it and dilute it to 1,000 mL. The solution shall be used on the day it prepared.
4.2.10 Sodium borohydride solution, 0.1 g/L: Weigh 2.0 g of sodium hydroxide and dissolve it with water, after that, add 0.1 g of sodium borohydride into it, after the sodium borohydride is dissolved, add water into it and dilute it to 1,000 mL. The solution shall be used on the day it prepared.
4.2.11 Thiourea-ascorbic acid mixture: Weigh 5.0 g of thiourea and 5.0 g of ascorbic acid respectively and dissolve them with water, after that, add 10 mL of nitric acid (4.2.2) into it, then add water into it and dilute it to 1,000 mL. The solution shall be prepared immediately before use.
4.2.12 Standard stock solution
Standard stock solutions may be prepared with standard substances or prepared according to the following method:
a) Arsenic standard stock solution, 100 mg/L: Accurately weigh 0.1320 g of arsenic trioxide (As2O3) (has been dried to a constant weight in a desiccator) and dissolve it with 10 mL of sodium hydroxide solution (4.2.7), and then transfer it to a 1,000-mL volumetric flask with an appropriate amount of water, then add 60 mL of nitric acid solution (4.2.8) into it and dilute it to scale with water, then mix it well.
b) Mercury standard stock solution, 100mg/L: Accurately weigh 0.135 4 g of dried mercury bichloride (HgCl2) and dissolve it with 60mL of nitric acid solution (4.2.8), after that, transfer it into a 1,000-mL volumetric flask and dilute it to scale with water, then mix it well.
Note: Unless otherwise specified, the standard stock solutions shall have a storage life of 6 months at a low temperature of 0℃ ~ 4℃. In case of turbidity, precipitation or color change, it shall be prepared again.
4.2.13 Standard working solution
4.2.13.1 Arsenic standard working solution, 100 μg/L: Pipet 1.00 mL of arsenic standard stock solution (4.2.12.1) and put it into a 100-mL volumetric flask, then dilute it to scale with water and shake it well to obtain the arsenic standard solution with a concentration of 1 mg/L. Then pipet 10.00 mL of standard solution (1 mg/L) and put it into a 100-mL volumetric flask, then dilute it to scale with water. The solution shall be used on the day it prepared.
4.2.13.2 Mercury standard working solution, 5.0 μg/L: Pipet 5.00mL of mercury standard stock solution (4.2.12.2) and put it into a 100-mL volumetric flask, then dilute it to scale with water and shake it well to obtain the mercury standard solution with a concentration of 5 mg/L. Then pipet 0.10 mL of standard solution (5 mg/L) and put it into a 100-mL volumetric flask (with a small amount of water), then add 6 mL of nitric acid (4.2.2) into it and dilute it to scale with water. The solution shall be used on the day it prepared.
4.3 Apparatus
4.3.1 Atomic fluorescence spectrophotometer: prepare sequential injection sampling device.
4.3.2 Hollow cathode lamp: arsenic lamp and mercury lamp.
4.3.3 Microwave digestion instrument.
4.3.4 Analytical balance: with a sensitivity of 0.1 mg.
4.3.5 Volumetric flask: 10mL, 25mL, 100mL and 1,000mL.
4.3.6 Filter membrane: same as 3.3.5.
4.3.7 Disposable syringe: same as 3.3.6.
4.3.8 Pipette: same as 3.3.7.
4.4 Analytical procedures
4.4.1 Specimen treatment
Weigh 0.200 g～0.250 g of specimen (accurate to 0.001 g), and place it into a microwave digestion tube, then add 3 mL of nitric acid (4.2.2), 2 mL of hydrogen peroxide (4.2.3) and 2 mL of fluoboric acid (4.2.4). After the safety valve is covered, place the digestion tube in a microwave digestion system (4.3.3), and keep it at (195±5) ℃ for 20 min. After digestion, transfer the solution to a 25-mL volumetric flask (4.3.5) and dilute it to scale with water after the solution is cooled to room temperature, and filter it with the water film (4.3.6) for later use.
Contents of GB/T 34673-2017
Foreword i
1 Scope
2 Normative references
3 Determination of 8 heavy metal contents through inductively coupled plasma atomic emission spectrometry
4 Determination of the content of arsenic and mercury with atomic fluorescence spectrophotometry
5 Test report
Annex A (Informative) Selected wavelengths for element determination with ICP-AES method
