Foreword
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 document is developed in accordance with the rules given in GB/T 1.1-2020 Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents.
This document is Part 6 of GB/T 5750 Standard examination methods for drinking water. The following parts of GB/T 5750 have been issued:
——Part 1: General principles;
——Part 2: Collection and preservation of water samples;
——Part 3: Water analysis quality control;
——Part 4: Organoleptic and physical indices;
——Part 5: Inorganic nonmetallic indices;
——Part 6: Metal and metalloid indices;
——Part 7: Aggregate organic indices;
——Part 8: Organic indices;
——Part 9: Pesticides indices;
——Part 10: Disinfection by-products indices;
——Part 11: Disinfectants indices;
——Part 12: Microbiological indices;
——Part 13: Radiological indices.
This document replaces GB/T 5750.6-2006 Standard examination methods for drinking water - Metal parameters. In addition to structural adjustment and editorial changes, the following main technical changes have been made with respect to GB/T 5750.6-2006:
a) The clause "Terms and definitions" has been added (see Clause 3 hereof);
b) 10 examination methods have been added (see 9.5, 9.6, 10.5, 13.2, 28.1, 28.2, 28.3, 29.1, 30.1 and 30.2 hereof);
c) One examination method has been changed (see 4.5 hereof; 1.5 of Edition 2006);
d) 13 examination methods have been deleted (see 4.2.2, 4.2.3, 4.2.4, 5.2, 5.4, 6.4, 7.4, 7.5, 9.3, 11.3, 11.4, 17.1 and 20.3 of Edition 2006).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This document was proposed by and is under the jurisdiction of the National Health Commission of the People's Republic of China.
The previous editions of this document are as follows:
——This document was firstly issued as GB/T 5750-1985 in 1985 and firstly revised as GB/T 5750.6-2006 in 2006;
——This is the second revision.
Introduction
The series of standards GB/T 5750 Standard examination methods for drinking water, as the recommended national standards for drinking water examination technology, are compatible with GB 5749 Standards for drinking water quality, and are also served as an important technical support of GB 5749. They provide examination methods for implementing GB 5749 and carrying out hygienic safety evaluation of drinking water.
GB/T 5750 consists of 13 parts.
——Part 1: General principles. It provides the basic principles and requirements for water quality examination.
——Part 2: Collection and preservation of water samples. It provides the basic principles, measures and requirements for water sample collection, preservation, management, transportation and sampling quality control.
——Part 3: Water analysis quality control. It provides quality control requirements and methods for water quality examination and testing laboratories.
——Part 4: Organoleptic and physical indices. It provides corresponding examination methods for organoleptic and physical indices.
——Part 5: Inorganic nonmetallic indices. It provides corresponding examination methods for inorganic nonmetallic indices.
——Part 6: Metal and metalloid indices. It provides corresponding examination methods for metal and metalloid indices.
——Part 7: Aggregate organic indices. It provides corresponding examination methods for aggregate organic indices.
——Part 8: Organic indices. It provides corresponding examination methods for organic indices.
——Part 9: Pesticides indices. It provides corresponding examination methods for pesticides indices.
——Part 10: Disinfection by-products indices. It provides corresponding examination methods for disinfection by-products indices.
——Part 11: Disinfectants indices. It provides corresponding examination methods for disinfectants indices.
——Part 12: Microbiological indices. It provides corresponding examination methods for microbiological indices.
——Part 13: Radiological indices. It provides corresponding examination methods for radiological indices.
Standard examination methods for drinking water - Part 6: Metal and metalloid indices
1 Scope
This document describes the methods for determination of aluminum, iron, manganese, copper, zinc, arsenic, selenium, mercury, cadmium, chromium (hexavalent), lead, silver, molybdenum, cobalt, nickel, barium, titanium, vanadium, antimony, beryllium, thallium, sodium, tin, tetraethyl lead, ethylmercury chloride, boron and asbestos in drinking water and those for determination of aluminum, iron, manganese, copper, zinc, arsenic, selenium, mercury, cadmium, chromium (hexavalent), lead, silver, molybdenum, cobalt, nickel, barium, titanium, vanadium, antimony, beryllium, thallium, sodium, tin, tetraethyl lead, ethylmercury chloride (purge and trap/gas chromatography - atomic fluorescence spectrometry), boron and asbestos in water sources.
This document is applicable to the determination of metal and metalloid indices in drinking water and water sources.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions 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 5750.1 Standard examination methods for drinking water - Part 1: General principles
GB/T 5750.3-2023 Standard examination methods for drinking water - Part 3: Water analysis quality control
GB/T 5750.5-2023 Standard examination methods for drinking water - Part 5: Inorganic nonmetallic indices
GB/T 6682 Water for analytical laboratory use - Specification and test methods
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 5750.1 and GB/T 5750.3-2023 apply.
4 Aluminum
4.1 Chrome azurol S spectrophotometric method
4.1.1 Minimum detectable mass concentration
The minimum detectable mass of this method is 0.20μg. If 25mL of water sample is taken, the minimum detectable mass concentration is 0.008mg/L.
Copper, manganese and iron in water can interfere with the determination. 1mL of ascorbic acid (100g/L) can eliminate the interference of 25μg of copper and 30μg of manganese. 2mL of mercaptoacetic acid (10g/L) can eliminate the interference of 25μg of iron.
4.1.2 Principle
In the range of pH 6.7 to pH 7.0, aluminum reacts with chrome azurol S in the presence of polyethylene glycol octylphenyl ether (OP) and cetylpyridinium bromide (CPB) to form a blue-green quaternary micelles, which can be quantified by colorimetry.
4.1.3 Reagents
4.1.3.1 Chrome azurol S solution (1g/L): Weigh 0.1g of chrome azurol S (C23H13O9SCl2Na3), dissolve it in 100mL of ethanol solution (1+1), and mix well.
4.1.3.2 Emulsifier OP solution (3+100): Pipette 3.0mL of emulsifier OP (C18H30O3) and dissolve it in 100mL of pure water.
4.1.3.3 Cetylpyridinium bromide (CPB) solution (3g/L): Weigh 0.6g of CPB (C21H36BrN), dissolve it in 30mL of ethanol [φ(C2H5OH)=95%], and then dilute the solution to 200mL with water.
4.1.3.4 Ethylenediamine-hydrochloric acid buffer solution (pH 6.7~pH 7.0): Pipette 100mL of anhydrous ethylenediamine (C2H8N2), add 200mL of pure water into it, cool the solution and then slowly add 190mL of hydrochloric acid (ρ20=1.19g/mL), and mix well. Add hydrochloric acid or ethylenediamine solution (1+2) respectively if the pH value is greater than 7 or less than 6, and adjust as per acidometer indication.
4.1.3.5 Aqueous ammonia (1+6).
4.1.3.6 Nitric acid solution [c(HNO3)=0.5mol/L].
4.1.3.7 Aluminum standard stock solution [ρ(Al)=1mg/mL]: Weigh 8.792g of aluminum potassium sulfate dodecahydrate [KAl(SO4)2·12H2O], dissolve it in pure water, and then dilute the solution to a constant volume of 500mL; or weigh 0.500g of pure metal aluminum sheet, dissolve it in 10mL of hydrochloric acid (ρ20=1.19g/mL), and then dilute the solution to a constant volume in a 500-mL volumetric flask with pure water. Store the solution in a polytetrafluoroethylene or polyethylene bottle. Alternatively, use the certified reference material.
4.1.3.8 Aluminum standard use solution [ρ(Al)=1μg/mL]: Dilute the aluminum standard stock solution to prepare the solution immediately before use.
4.1.3.9 p-nitrophenol ethanol solution (1.0g/L): Weigh 0.1g of p-nitrophenol and dissolve it in 100mL of ethanol [φ(C2H5OH)=95%].
4.1.4 Apparatuses
4.1.4.1 Colorimetric tube with stopper: 50mL, which shall be soaked in nitric acid (1+9) to remove aluminum before use.
4.1.4.2 Acidometer.
4.1.4.3 Spectrophotometer.
4.1.5 Test procedures
4.1.5.1 Pipette 25.0mL of water sample into a 50-mL colorimetric tube with stopper.
4.1.5.2 Take another eight 50-mL colorimetric tubes and add 0mL, 0.20mL, 0.50mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL and 5.00mL of aluminum standard use solution to respective tubes, and then add pure water to each tube until 25mL.
4.1.5.3 Add one drop of p-nitrophenol ethanol solution to each tube, mix well, add aqueous ammonia (1+6) dropwise until the solution becomes light yellow, and then add nitric acid solution until the yellow color of the solution disappears, and finally add two more drops of nitric acid solution.
4.1.5.4 Add 3.0mL of chrome azurol S solution to each tube, mix well, then add 1.0mL of emulsifier OP solution, 2.0mL of CPB solution and 3.0mL of ethylenediamine-hydrochloric acid buffer solution, dilute the solution to 50mL with pure water, mix well, and then let it still for 30min.
4.1.5.5 Measure the absorbance at a wavelength of 620nm using a 2-cm cuvette with a reagent blank as reference.
4.1.5.6 Plot the standard curve and find out the mass of aluminum in the water sample tube from the curve.
Note: When the water contains copper or manganese, add 1mL of ascorbic acid solution (100g/L) to eliminate the interference of 25μg of copper and 30μg of manganese. When the water contains iron, add 2mL of mercaptoacetic acid solution (10g/L) to eliminate the interference of 25μg of iron.
4.1.6 Test data processing
The mass concentration of aluminum in the water sample shall be calculated using Equation (1):
(1)
where,
ρ(Al)——the mass concentration of aluminum in the water sample, mg/L;
m——the mass of aluminum in the water sample tube found from the standard curve, μg;
V——the volume of water sample, mL.
4.1.7 Precision and accuracy
Among all the five laboratories, the relative standard deviations of the water samples with mass concentrations of 20μg/L and 160μg/L are less than 5% and the recovery rates range from 94% to 106%.
Foreword II
Introduction IV
1 Scope
2 Normative references
3 Terms and definitions
4 Aluminum
5 Iron
6 Manganese
7 Copper
8 Zinc
9 Arsenic
10 Selenium
11 Mercury
12 Cadmium
13 Chromium (hexavalent)
14 Lead
15 Silver
16 Molybdenum
17 Cobalt
18 Nickel
19 Barium
20 Titanium
21 Vanadium
22 Antimony
23 Beryllium
24 Thallium
25 Sodium
26 Tin
27 Tetraethyl lead
28 Ethylmercury chloride
29 Boron
30 Asbestos
