Copper. Methods for the determination of copper. Methods for determining copper in various substances Method for determining copper
Copper sulfate enhances the biological growth of agricultural crops, algae bacteria, is part of human nutrition and does not belong to toxic substances, if the content does not exceed the established norms - up to 20 mg / m 3.
Copper ore has up to 30% pure copper
In order to carry out the determination of copper, its share in various substances use the following methods:
- chemical;
- quantitative;
- photometric.
At the moment, a wide variety of methods have been developed for determining the amount of copper in the composition of other substances, each separate way has both advantages and disadvantages.
Chemical Methods
With the help of various chemical compositions it is possible to influence the splitting of molecules and atoms of a substance and to isolate its constituent parts. Chemical methods include the electrolytic method of measuring the copper part in alloys of other metals, it is carried out using the following elements:
- acetylene;
- tartaric acid;
- aqueous ammonia;
- ammonium nitrate;
- disodium salt;
- ethanol;
- cuprizone.
To begin with, the copper composition (sampling) is weighed, then sent to the prepared reagent solution, in which the sample must be completely dissolved. The resulting liquid is heated, while nitrogen oxides are removed, the purified solution is diluted with water and heated again to 40 ° C.
After that, the mass is ready for the electrolysis process - electrodes, usually made of platinum, are immersed in the solution, a current of 2.2 V is connected, and with constant stirring, the process of copper extraction begins.
For control, you can perform a repeated electrolysis process, for this the electrodes are lowered into the liquid, below the level of the selected copper and the current is connected. If the initial process went correctly, then no metal deposits will form during the control procedure. The copper cathode obtained as a result of such splitting is washed with water without disconnecting the electric current, then treated with ethyl alcohol and dried. The resulting copper cathode is weighed, and the result is compared with the original weight. Thus, they calculate specific gravity copper in matter.
A variety of chemical methods for the determination of copper differ in the composition of the solutions, the appropriateness of which is determined depending on the expected impurities of foreign substances, but the principle of operation is the same.
Quantitative Methods
Methods for quantitative determination of the mass of copper in the total volume of the metal are used mainly for alloys with nickel, bronze and zinc. In the process of exposure to the substance, copper is deposited and in this form it can be measured. Inorganic and organic elements are used for precipitation. TO inorganic substances used to determine copper include:
Organic substances that are used in the quantitative determination of copper include:
- oxyquinoline-8, it precipitates copper in combination with ammonia and alkaline solution, when the precipitate is heated, copper oxide is formed. This method is used for complex alloys in which aluminum, tin, lead, arsenic, chromium, iron are present;
- α-benzoinoxime in an alcohol solution is able to precipitate metal in the form of flakes, this method is not applicable if nickel is present in the composition;
- potassium iodide, it is used in a neutral and acidic environment, it is not used if iron, antimony and arsenic are included in the alloy.
Before using any method, it is necessary to determine the composition of the alloy in advance, this can be done experimentally, by heating (the metal changes color), evaporation (the metal precipitates), using filters.
Photometric methods
To determine copper in various material compositions, a photometric method is used, its advantages are a high accuracy of measuring the quantitative composition, ease of use, it does not require expensive equipment. This method can be used with various active substances:
Photometric analysis is carried out on special. equipment
- cuprizone;
- lead diethyldithiocarbamate.
The essence of the photometric determination of copper is to fix the intensity of the color of the material that has passed through a concentrated solution. For this solution use:
- ammonia;
- ammonium citrate solution;
- lead diethyldithiocarbamate;
- sodium sulfate.
The substance in which it is necessary to determine copper is passed through the above solutions, while it is important to observe the proportions, then subjected to photometry. The apparatus of a single-beam photometer consists of a tungsten lamp, a movable diaphragm, a light filter, a photocell, and a microammeter.
Determination of copper in water and soil
The main methods for determining copper in waste, sewer, river, sea water, as well as in soil, include:
- atomic absorption direct;
- atomic absorption with the use of chelation
- atomic absorption with processing in a graphite furnace
To determine the metal in the soil, the method using a graphite furnace is considered the most reliable.
Atomic absorption analysis for the determination of copper in water
The essence of this method lies in the fact that a soil sample is placed in a graphite pipe, dehydrated by burning and sprayed. The sputtering process involves the separation of a substance into atoms, which are then filtered and the desired metal is isolated from them. Any photometric copper determination method can be used to evaluate a soil sample.
To determine the metal in water, the most accurate and comprehensive will be the atomic absorption method using chelation, it allows you to analyze any water, even sea water, which is not possible with the direct atomic absorption method. The essence of this method is the dissolution of metal particles with the help of dithiocarbamic acid, water is evaporated from the obtained extract and placed in a spectrophotometer, which determines the presence of copper and its concentration by color.
Video: Copper and Iron Based Alloys
The essence of the method. The method is based on the formation of a complex compound of copper ions with ammonia, which has an intense blue-violet color. The color of copper ammonia is due to d >d * transitions due to the splitting of the ground electronic state of copper ions in the field of ligands. Since the stability of the resulting complexes differ little, the solution will contain a mixture of several copper ammoniates, the quantitative ratio of which depends on the concentration of ammonia present in the solution. The molar absorption coefficient of copper tetraammine at l=640 nm is 1 10 2 . The low value of e l makes it possible to determine sufficiently high concentrations of copper ions.
Reagents:
Working solution of copper salt containing 1 mg of copper in 1 ml. To prepare this solution, weigh 3.931 g. copper sulfate CuSO 4 5H 2 O is dissolved in 25 ml of a 2M solution of sulfuric acid, the volume of the solution is adjusted to 1 liter with distilled water.
Progress:
Preparation of standard solutions. Prepare 6 standard solutions containing 5.0; 7.5; 10; 12.5; 15; 17.5 mg of copper in 50 ml. To do this, 5.0 is transferred into volumetric flasks per 50 ml, respectively; 7.5; 10; 12.5; 15; 17.5 ml of the stock solution, add 10 ml of 5% ammonia solution to each flask with a measuring cylinder and bring the volume to 50 ml (to the mark) with distilled water. In 10 minutes. start measuring. The work is carried out with a light filter No. 8. Use 20 ml cuvettes. With this light filter, the standard solutions are alternately photometered. Each measurement must be repeated 3 times. According to the average values in the absorption coordinates, a calibration graph is built.
Getting results. Get a solution of sulfate copper (II) or natural concentrated brine, add 10 ml of 5% ammonia solution and bring the volume to 50 ml with distilled water. The prepared solution after 10 minutes. photometry. The measurements are repeated 5 times. Using the built calibration graph, find the copper content in the analyzed solution.
Construction of a calibration graph.
We prepared a series of solutions of copper chloride with known concentrations from a 3.6 mmol/l solution. To obtain a solution with a concentration of 1.8 mM, it is necessary to take 50 ml of the initial solution and bring it to 100 ml, and similarly prepare solutions with the concentrations indicated in Table 3.2.
The optical density of the solutions was measured and the results were entered in Table 3.2.
Table 3.2
Built a graph of the dependence of optical density on the concentration of copper.
The graph shows that the Bouguer-Lambert-Beer law is applicable to copper. That is, with an increase in the concentration of copper in the solution, the optical density of the solution increases, while the dependence is linear and originates at the origin of coordinates.
Rice. 3.1 Calibration curve for copper content
page 1
page 2
page 3
page 4
page 5
page 6
page 7
page 8
page 9
page 10
page 11
page 12
page 13
page 14
page 15
page 16
page 17
page 18
page 19
FEDERAL AGENCY
FOR TECHNICAL REGULATION AND METROLOGY
Foreword
Goals and principles of standardization in Russian Federation established by the Federal Law of December 27, 2002 No. 184-FZ "On Technical Regulation", and the rules for the application of national standards of the Russian Federation - GOST R 1.0-2004 "Standardization in the Russian Federation. Basic Provisions»
About the standard
1 PREPARED by the Federal State Unitary Enterprise "All-Russian Research Center for Standardization, Information and Certification of Raw Materials, Materials and Substances" (FSUE "VNITSSMV") based on its own authentic translation into Russian of the standard specified in paragraph 4
2 INTRODUCED by the Office of Technical Regulation and Standardization of the Federal Agency for Technical Regulation and Metrology
3 APPROVED AND INTRODUCED BY Order No. 1109-st of December 27, 2010 of the Federal Agency for Technical Regulation and Metrology
4 This standard is identical to ASTM D 1688-02 Standard Test Methods for Copper in Water.
The name of this standard has been changed relative to the name of the specified standard to bring it into line with GOST R 1.5-2004* (subsection 3.5).
* In part of sect. 8 and appendices Zh, I, K replaced by GOST R 1.7-2008.
When applying this standard, it is recommended to use instead of the ASTM reference standards the corresponding national standards of the Russian Federation and interstate standards, information about which is given in the additional appendix YES
5 INTRODUCED FOR THE FIRST TIME
6 REVISION. December 2011
Information about changes To present standard published V annually published informational index "National standards", A text changes And amendments - V monthly published information signs "National standards". IN case revision (substitutions) or cancellation present standard corresponding notification will published V monthly published informational index "National standards". Relevant information, notification And texts are placed Also V informational system general use - on official website Federal agencies By technical regulation And metrology V networks Internet
|
1 area of use. 3 3 Terms and definitions. 4 4 The importance of determining copper. 4 5 Purity of reagents. 4 6 Sampling. 5 Method A is the direct atomic absorption method. 5 7 Scope. 5 8 The essence of the method. 5 9 Interfering factors.. 5 10 Equipment. 6 11 Reagents and materials.. 6 12 Standardization. 6 13 Testing. 7 14 Processing of results. 7 15 Precision and deviation. 7 Method B - atomic absorption method using extraction with chelation.. 8 16 Scope. 8 17 The essence of the method. 8 18 Interfering factors.. 9 19 Equipment. 9 20 Reagents and materials.. 9 21 Standardization. 9 22 Testing. 10 23 Processing of results. eleven 24 Precision and deviation. eleven Method C is an atomic absorption method using a graphite furnace. 12 25 Scope. 12 26 The essence of the method. 12 27 Interfering factors.. 12 28 Equipment. 12 29 Reagents and materials.. 13 30 Standardization. 13 31 Testing. 13 32 Processing of results. 14 33 Precision and deviation. 14 34 Quality control (QC) 14 Annex DA (informative) Information on the compliance of ASTM reference standards with reference national standards of the Russian Federation (and interstate standards in force in this capacity) 17 |
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
WATER
Methods for determining copper
water. Methods for determination of copper
Introduction date - 2012-07-01
1 area of use
1.1 This International Standard specifies three atomic absorption spectrophotometric methods for the determination of copper in water:
1.2 Dissolved or total copper can be determined by these methods. To determine dissolved copper, filtration is carried out through a 0.45 µm membrane filter (No. 325) during water sampling. Flow filtration is preferred.
1.3 The values stated in SI units are standard. Values in brackets are for information only.
1.4 This standard does not purport to address all the safety precautions associated with its use. The user of this standard is responsible for developing appropriate safety and health practices and for determining whether legal restrictions are appropriate before using it. Special safety instructions are given in notes 3, 5, 8 and 13.
2 Normative references
This standard uses normative references to the following standards:
ASTM D 1066, Practice for sampling steam (ASTM D 1066, Practice for sampling steam) 1)
ASTM D 1068, Test methods for iron in water 1)
ASTM D 1129 Terminology relating to water (ASTM D 1129, Terminology relating to water) 1)
ASTM D 1192, Specification for equipment for sampling water and steam in closed conduits (ASTM D 1192, Specification for equipment for sampling water and steam in closed conduits) 1)
ASTM D 1193 Specification for reagent water (ASTM D 1193, Specification for reagent water) 1)
ASTM D 1687, Test methods for chromium in water 1)
ASTM D 1691, Test methods for zinc in water 1)
ASTM D 1886, Test methods for nickel in water 1)
ASTM D 2777, Practice for determination of precision and bias of applicable methods of committee D-19 on water) 1)
ASTM D 3370, Practices for sampling water from closed conduits 1)
ASTM D 3557, Test methods for cadmium in water 1)
ASTM D 3558, Test methods for cobalt in water 1)
ASTM D 3559, Test methods for lead in water 1)
ASTM D 3919, Practice for measuring trace elements in water by graphite furnace atomic absorption spectrophotometry 1)
ASTM D 4841, Practice for estimation of holding time for water samples containing organic and inorganic constituents) 1)
ASTM D 5810, Guide for spiking into aqueous samples 1)
ASTM D 5847, Practice for writing quality control specifications for standard test methods for water analysis) 2)
1) Annual Book of ASTM Standards, Vol. 11.01., Volume 11.01.
2) Annual Book of ASTM Standards, Vol. 11.02., Volume 11.02.
3 Terms and definitions
3.1 This standard uses the terms used in ASTM D 1129.
4 Importance of copper determination
4.1 Copper occurs in natural minerals mainly in the form of sulfide, oxide or carbonate. It makes up approximately 0.01% of the earth's crust and is industrially extracted from ores such as chalcoperite (CuFeS 2). Copper is also found in biological complexes of hemocyanin.
4.2 Copper enters water sources as a result of the natural process of mineral dissolution; from industrial wastewater during the processing of copper sulfate; in the control of biological growth in some tanks and distribution systems; at corrosion of copper alloys of water pipes. Copper can be found in significant concentrations in sewage mining, munitions and most electroplating and manufacturing or industries. Copper may be present in a simple ionic form or as one of many complexes of groups such as cyanides, chlorides, ammonia or organic ligands.
4.3 Although these salts, in particular copper sulfate, enhance the biological growth of some algae and bacteria, copper is considered an essential part of the human diet and is not a toxic chemical at concentrations commonly found in water samples.
5 Purity of reagents
5.1 The reagents used must be chemically pure (chemically pure) class. Unless otherwise stated, this means that all reagents comply with specifications Committee on Analytical Reagents of the American Chemical Society (ASTM), where specifications for these reagents can be obtained. Substances of other purity classes can be used if it is initially determined that the reagent is sufficiently pure and cannot lead to a decrease in the accuracy of the measurement.
5.2 Purity of water (unless otherwise specified) is understood to be laboratory water (pure for analysis - analytical grade) of ASTM D 1193 class I. Other laboratory water classes may be used, provided that first of all the degree of its purity has been established, which cannot lead to a decrease in the accuracy (precision) of measurements and an increase in measurement deviations. Class II water was used in the interlaboratory round robin test according to the methods given.
6 Sampling
6.1 Samples are taken in accordance with ASTM D 1066, ASTM D 1192 and ASTM D 3370.
6.2 Samples should be treated with nitric acid (HNO 3 ) specific gravity 1.42 to a pH value of 2 or less immediately after sampling, usually about 2 ml/l of nitric acid is required. If only dissolved copper is determined, the sample is filtered through a 0.45 µm membrane filter (No. 325) before acidification. The retention time of samples can be calculated in accordance with ASTM D 48.
Method A - direct atomic absorption method
7 Scope
7.1 This method determines the dissolved and total recoverable copper in most waters, including wastewater.
7.2 This method is applicable in the range of copper concentrations from 0.05 to 5 mg/l. The range can be extended to concentrations greater than 5 mg/L by diluting the sample.
7.3 Collaborative test data obtained on laboratory water, river water, tap water, ground water, lake water, pre-treated refinery wastewater and two raw wastewater. Information about precision and deviation in measurements is not applicable to other waters.
8 Essence of the method
8.1 Copper is determined using atomic absorption spectrophotometry. The filtered sample with dissolved copper is introduced (sucked) into the device without pretreatment. To determine the total amount of recoverable copper in the sample, the sample is injected after treatment with a mixture of hydrochloric and nitric acids and filtration. The same preparation procedure can be used as used to determine total recoverable cadmium (ASTM D 3557 method), chromium (ASTM D 1687 method), cobalt (ASTM D 3558 method), iron (ASTM D 1068 method), lead (ASTM D 3559 method), manganese (ASTM D 858 method), nickel (ASTM D 1886 method), and zinc (ASTM D 1691 method).
9 Confounding factors
9.1 Sodium, potassium, sulfates and chlorides (8000 mg/l each), calcium and magnesium (5000 mg/l each), nitrates (2000 mg/l), iron (1000 mg/l), cadmium, lead, nickel, zinc , cobalt, manganese and chromium (10 mg/l each) do not interfere with the determination of copper in water.
9.2 In some waters, background correction or the use of a chelate extraction technique (Method B) may be necessary to determine trace amounts of copper.
Note 1 - It is necessary to follow the instructions of the manufacturer of the device when using special techniques adjustments.
10 Equipment
10.1 Atomic absorption spectrophotometer, designed to operate in the 324.7 nm wavelength region.
NOTE 2 The manufacturer's instructions should be consistent with all instrument parameters. A wavelength other than 324.7 nm may be used if it has been determined beforehand that it is equally suitable.
10.1.1 Hollow cathode lamp on copper. Hollow cathode lamps are also suitable for many elements.
10.2 Oxidizer - see 11.6.
10.3 Fuel - see 11.7.
10.4 Pressure reducing valves. The supply of fuel and oxidizer should be carried out at pressures slightly higher than the operating pressure regulated in the device by the corresponding valves.
11 Reagents and materials
11.1 Copper solution, original (1.0 ml = 1.0 mg Cu): Dissolve 1.000 g of electrolytic copper in a 250 ml beaker in a mixture of 15 ml of nitric acid (HNO 3) (specific gravity 1.42) and 15 ml water. Slowly add 4 ml of sulfuric acid (H 2 SU 4 , specific gravity 1.84) (1 + 1) and heat until sulfuric anhydride (SO 3) begins to evolve. Cool, rinse the beaker with water and dilute with water to 1 liter. A commercial stock solution of the same purity may also be used.
11.2 Copper solution, standard (1.0 ml = 0.1 mg Cu): Dilute 100.0 ml of copper stock solution with water to 1 L.
11.3 Hydrochloric acid (specific gravity - 1.19). Concentrated hydrochloric acid (HCl).
NOTE 3—If a high purity reagent is obtained, then HCl is distilled or a spectral grade acid is used.
Attention: Distillation of HCl produces an azeotropic mixture (HCl concentration approximately 6N). Therefore, whenever concentrated HCl is specified for the preparation of a reagent or method, double the indicated volume is used for distillation.
11.4 Nitric acid (specific gravity - 1.42). Concentrated nitric acid (HNO 3).
NOTE 4—If a high purity reagent is obtained, distill HNO 3 or use an acid of spectral purity.
11.5 Nitric acid (1 + 499). Add 1 volume of HNO 3 (specific gravity 1.42) to 499 volumes of water.
11.6 Oxidizer
11.6.1 Air passed through an appropriate filter to remove oil, water and other foreign matter is normally used as the oxidizing agent.
11.7 Fuel
11.7.1 Acetylene. Usually standard acetylene is used as fuel. Acetone present in acetylene cylinders can interfere with analytical results. The balloon is refilled at 50 p.s.i.g (345 kPa).
Note 5 - Warning- Purified grade acetylene, containing a special proprietary solvent, to a greater extent than acetone, must not be used with PVC tubing, as the loss of strength of the pipelines can lead to a dangerous situation.
12 Standardization
12.1 Prepare 100 ml of a blank sample and at least four standard solutions in the expected concentration range of the samples to be analyzed by diluting the copper standard solution (11.2) with HNO 3 (1 + 499). Prepare standard solutions immediately before testing.
12.2 When determining the total recoverable copper, add 0.5 ml HNO 3 (specific gravity - 1.42) and continue the test in accordance with 13.2 - 13.4. When determining dissolved copper, continue with the test in accordance with 13.5.
12.3 Inject (by aspiration) the blank and standard solutions and record the instrument readings. Enter HNO 3 (1 + 499) in between the analysis of each solution.
12.4 Plot an analytical curve by plotting the absorbance values against the concentration of copper in each standard solution. Alternatively, determine the copper concentration directly from the meter.
13 Testing
13.1 Place 100.0 ml of the well mixed acidified sample in a 125 ml beaker or flask.
NOTE 6—If only dissolved copper is to be determined, start at 13.5.
13.2 Add 5 ml HCl (specific gravity 1.19) to each sample.
13.3 Heat the samples on a steam bath or hot plate in a well-ventilated fume hood until the volume is reduced to 15 to 20 ml without bringing the samples to a boil.
NOTE 7—If the analyzed samples contain a significant amount of suspended material, the amount of volume reduction is at the discretion of the analyst.
13.4 Cool and filter the samples into a 100 ml volumetric flask through an appropriate filter, such as a fine acid-washed cloth or ashless filter. Wash the filter paper two or three times with water and dilute the samples to the desired volume.
13.5 Introduce each filtered and acidified sample into the atomic absorption spectrophotometer (by suction) and determine the absorbance or concentration at 324.7 nm. Enter a solution of HNO 3 (1 + 499) in the intervals between the analysis of each sample.
14 Processing results
14.1 Calculate the concentration of copper in each sample in milligrams per liter using the analytical curve, or alternatively use the meter reading (12.4).
15 Precision and bias
15.1 Interlaboratory testing of this method was carried out in ten laboratories, five of which had two operators. Each of the 15 operators performed determinations at three levels over three days on laboratory water samples and selected water samples for a total of 270 determinations.
15.2 Collaborative test data obtained on laboratory water, river water, tap water, ground water, lake water, pre-treated refinery wastewater, two raw wastewater. For other materials, these data are not applicable.
15.3 The precision and bias of this method is in accordance with ASTM D 2777-77, which is applied to data obtained from collaborative tests. In accordance with the assumption made in 1.4 of ASTM D 2777-98, these values of precision and deviation correspond to existing requirements for round-robin tests according to the methods of ASTM D 19 Committee.
15.4 Precision
in class II laboratory water
S O = 0.020 X + 0,035; (1)
S T = 0.052 X + 0,123; (2)
in river, tap, ground, lake or waste water
S O=0.016 X + 0,033; (3)
S T = 0.060 X + 0,039, (4)
Where S O - precision of results obtained by one operator;
S T is the overall precision;
X- determined concentration of copper, mg/l.
15.5 Deviation
The results of the extraction of known amounts of copper are shown in table 1.
Table 1 - Determination of limit deviations according to method A
|
Entered amount of Cu, mg/l |
A certain amount of Cu, mg/l |
Limit deviation, % |
|
|
laboratory water |
|||
|
Water (river, tap, ground, lake) or waste water |
|||
Method B - atomic absorption method using extraction with chelation
16 Scope
16.1 This method determines the dissolved and total recoverable copper in most waters, including marine waters.
16.2 This method is applicable in the range of copper concentrations from 50 to 500 µg/l. The range can be extended to concentrations greater than 500 µg/L by diluting the sample.
16.3 Interlaboratory test data obtained on laboratory water, river water, tap water and 50% artificial sea water and synthetic sea water with NaCl (50,000 mg/l). The obtained information on precision and deviation in measurements is not applicable to other waters.
17 Essence of method
17.1 Copper is determined using atomic absorption spectrophotometry. The dissolved or recovered element is chelated with pyrrolidine dithiocarbamic acid and then extracted with chloroform. The extract is evaporated to dryness, treated with hot nitric acid to destroy organic matter, dissolved in hydrochloric acid and diluted to a certain volume with water. A portion of the resulting solution is then injected (sucked) into an air-acetylene flame spectrophotometer. The sample treatment procedure or that described in 8.1 is used to determine the total recoverable copper. The same chelating extraction procedure is used to determine cadmium (ASTM D 3557 method), cobalt (ASTM D 3558 method), iron (ASTM D 1068 method), lead (ASTM D 3559 method), nickel (ASTM D 3559 method). ASTM D 1886) and zinc (ASTM D 1691 method).
18 Confounding factors
18.1 See section 9.
19 Equipment
19.1 Use the equipment specified in section 10.
20 Reagents and materials
20.1 Bromophenol blue indicator solution (1 g/l): Dissolve 0.1 g of bromophenol blue in 100 ml of 50% ethanol or isopropanol.
20.2 Chloroform (CHCl3).
20.3 Copper solution, original (1.0 ml = 1.0 mg Cu): Dissolve 1.000 g of electrolytic copper in a 250 ml beaker in a mixture of 15 ml of nitric acid (HNO 3) (specific gravity 1.42) and 15 ml water. Slowly add 4 ml of sulfuric acid (H 2 SO 4) (specific gravity - 1.84) (1 + 1) and heat until sulfuric anhydride (SO 3) begins to evolve. Cool, rinse the beaker with water and dilute with water to 1 liter. It is allowed to use a commercial stock solution of the same purity.
20.4 Copper solution, intermediate (1.0 ml = 10 µg Cu): dilute with water 10.0 ml stock copper solution and 1 ml nitric acid (HNO 3 ) (specific gravity 1.42) to 1 L.
20.5 Copper solution, standard (1.0 ml = 1.0 µg Cu): Immediately before use, dilute 10.0 ml of intermediate copper solution to 100 ml with water. During analysis, this standard solution is used to prepare working standard solutions.
20.6 Hydrochloric acid (specific gravity - 1.19). Concentrated hydrochloric acid (HCl) (see note 3).
20.7 Hydrochloric acid (1 + 2). Add 1 volume of HCl (specific gravity 1.19) to 2 volumes of water.
20.8 Hydrochloric acid (1 + 49). Add 1 volume of HCl (specific gravity 1.19) to 49 volumes of water.
20.9 Nitric acid (specific gravity 1.42). Concentrated nitric acid (HNO 3) (see note 4).
20.10 Pyrrolidine dithiocarbamic acid solution in chloroform: Add 36 ml of pyrrolidine to 1 L of chloroform (CHCl 3 ). The solution is cooled and 30 ml of carbon disulfide (CS 2 ) are added in small portions, stirring in a circular motion between the addition of CS 2 . Dilute the CHCl 3 solution to a volume of 2 L. The reagent is stored in a cool and dark place and used within a few months.
Note 8 - Beforebefore- All components of this reagent are highly toxic. Carbon disulfide is highly flammable. Attention: Preparation and use should be done in a well ventilated fume cupboard.
20.11 Sodium hydroxide solution (100 g/L): Dissolve 100 g sodium hydroxide (NaOH) in water and dilute to 1 L with water.
20.12 Oxidizer, see 11.6.
20.13 Fuel - see 11.7.
21 Standardization
21.1 Prepare a blank and sufficient standard solutions containing 0.0 to 50.0 µg copper by diluting 0.0 to 50.0 ml portions of the copper standard solution (20.5) to 100 ml with water.
21.2 To determine the total recoverable copper, use 125 ml beakers or flasks to which 0.5 ml of nitric acid (HNO 3 ) (specific gravity 1.42) is added and the test of 22.2 to 22.15 is carried out. For the determination of dissolved copper, use 250 ml separating funnels and carry out the test of 22.5 to 22.15.
21.3 Plot an analytical curve by plotting the absorbance of the standard solutions against the concentration of copper. Alternatively, the copper concentration can be determined directly from the meter.
22 Testing
22.1 A well-mixed acidified sample containing less than 50.0 µg of copper (not more than 100 ml) is placed in a 125 ml beaker or flask and diluted to 100 ml with water.
NOTE 9—To determine only dissolved copper, measure the volume of a filtered and acidified sample containing less than 50.0 µg of copper (not more than 100 ml) into a 250 ml separating funnel and carry out the determination starting from 22.5.
22.2 Add 5 ml of hydrochloric acid (HCl) (specific gravity 1.19) to each sample.
22.3 Heat the sample on a steam bath or hotplate in a well-ventilated fume hood until the volume is reduced to 15 ml to 20 ml without boiling.
NOTE 10—When analyzing seawater samples and samples containing a significant amount of suspended material, the volume of the evaporated sample is chosen by the analyst.
22.4 Cool and filter the samples through a filter consisting of a fine acid-washed cloth or ashless paper into a 250 ml separating funnel. Wash the filter two or three times with water and make up to 100 ml with water.
22.5 Add 2 drops of bromophenol blue indicator solution and mix thoroughly.
22.6 To the resulting solution, add NaOH (1 + 49) dropwise until the blue color disappears, then add 2.5 ml of HCl (1 + 49) in excess, adjusting the pH of the solution to 2.3.
NOTE 11 Adjusting the pH to a certain value can be done with a pH meter instead of using an indicator.
22.7 Add 10 ml of a solution of pyrrolidine dithiocarbamic acid reagent in chloroform and shake vigorously for 2 minutes. (Warning- See note 8).
22.8 Cover the neck of the separating funnel with cotton, allow the phases to separate, and pour the CHCl 3 phase into a 100 ml beaker.
22.9 Repeat the extraction with 10 ml of chloroform (CHCl 3 ) and pour off the CHCl 3 layer into the same beaker.
NOTE 12—If color still remains in the CHCl 3 extract, re-extract the aqueous phase until the CHCl 3 layer is colorless.
22.10 Place the beaker on the base of an electric hotplate on low heat or in a steam bath and let it evaporate to near dryness, then stop heating and allow the residual solvent to evaporate without heating.
NOTE 13 - Precaution - Work is carried out in a well-ventilated fume cupboard.
22.11 Hold the beaker at a 45° angle and slowly add 2 ml HNO 3 (specific gravity -1.42) dropwise, then swirl the beaker to bring the acid into the precipitate more efficiently and completely.
22.11.1 If acid is added with the beaker upright, it may cause chemical reaction accompanied by a large release of heat and splashing.
22.12 Place the beaker on the base of an electric hotplate on low heat or in a steam bath and evaporate to near dryness. Remove the beaker from the heater and allow the residual solvent to evaporate without heating.
22.13 Add 2 ml HCl (1 + 2) to the beaker and, while heating, stir for 1 min.
22.14 Cool the solution, transfer to a 10 ml volumetric flask and dilute to volume.
22.15 Introduce the sample (by aspiration) into the instrument and take a scale reading or determine the concentration at a wavelength of 324.7 nm according to 12.4.
23 Processing results
23.1 Determine the mass of copper in micrograms in each sample according to the analytical curve or alternatively by multiplying the direct meter reading in units of copper concentration by 10 ml (21.3). Calculate the concentration of copper, µg/l, in the initial sample using the formula
Copper = (1000 B)/A, (5)
Where A- the volume of the initial sample, ml;
IN is the mass of copper in the sample, μg.
24 Precision and bias
24.1 Interlaboratory testing of this method was carried out in six laboratories, two of which had two operators. Each operator analyzed the samples at three concentration levels. The total number of determinations was 120.
24.2 Interlaboratory test data obtained on laboratory water, river water, tap water, ground water, 50% artificial sea water and synthetic sea water with NaCl (50,000 mg/l). For other materials, these data are not applicable.
24.3 The precision and bias of this method are in accordance with ASTM D 2777-77, which is applied to this round-robin test. In accordance with the assumption of 1.4 ASTM D 2777-98, these values of precision and deviation correspond to the existing requirements for interlaboratory tests according to the methods of the Committee ASTM D 19.
24.4 Precision
The single operator and overall precision of this method over the indicated range is expressed as follows:
in class II laboratory water
S O=0.119 X + 9; (6)
S T = 0.247 X + 47; (7)
in river, tap, ground or sea water
S O = 27; (8)
S T = 0.270 X + 42, (9)
Where S O - precision obtained by one operator, µg/l;
S T - overall precision, µg/l;
X- determined concentration of copper, μg/l.
24.5 Deviation
The results of extraction of known amounts of copper are shown in table 2.
Table 2 - Determination of limit deviations according to method B
|
Limit deviation, % |
Statistical significance, 95% confidence level |
||
|
laboratory water |
|||
|
Water (river, tap, ground) or sea water |
|||
Method C - atomic absorption method using a graphite furnace
25 Scope
25.1 This method determines the dissolved and total recoverable copper in most waters and wastewaters.
25.2 This method is applicable in the range of copper concentrations from 5 to 100 µg/L. The range can be increased or decreased by changing the injection volume or instrument settings. High concentrations are diluted before being analyzed by direct injection (suction) into an atomic absorption spectrophotometer (see method A).
25.3 This test method applies to laboratory water, filtered tap water, condensate from coal gasification processes expressed in Btu (British Thermal Units), lake water, well water and water from industrial processes. It is the user's responsibility to ensure that this method is valid for other materials.
26 Essence of method
26.1 Copper is determined by atomic absorption spectrophotometry using a graphite furnace. The sample is placed in a graphite tube dehydrated to dryness, incinerated (pyrolyzed or ashed) and pulverized (subjected to atomization). Because a graphite furnace is used, the sample is atomized much more efficiently than in a flame; it is also possible to detect elements at lower concentrations in a small sample volume. The absorption signal produced by atomization is recorded and compared with a standard. General guidance on the use of a graphite furnace is given in ASTM D 3919.
26.2 Dissolved copper is determined on a filtered sample without pretreatment.
26.3 Total recoverable copper is determined after acid treatment and filtration. Due to the interference associated with the presence of chlorides, the use of hydrochloric acid for any treatment or dissolution step should be avoided. If suspended material is not present in the sample, then such processing and filtration can be omitted.
27 Confounding factors
27.1 To determine the degree of influence of interfering factors in procedures using a graphite furnace, the analyst should refer to ASTM D 3919.
28 Equipment
28.1 Atomic absorption spectrophotometer, designed to operate in the 324.7 nm wavelength region with background correction.
NOTE 14—A wavelength other than 324.7 nm may be used if it has been shown to be appropriate. Greater linearity can be obtained at high concentrations by using wavelengths with less sensitivity.
NOTE 15—The manufacturer's instructions should be followed when selecting instrument parameters.
28.2 Lamp with hollow cathode on copper. A lamp with a single element is preferred, but lamps with more elements can also be used.
28.3 Graphite furnace, capable of reaching the necessary temperatures for the atomization of the elements of interest.
28.4 Graphite tubes compatible with furnace design. Pyrolytically coated graphite tubes are recommended.
28.5 Microliter pipettes with detachable tips. Sizes can range from 1 to 100 µl.
28.6 Data acquisition and conversion devices, computer or microprocessor controlled devices or strip chart recorders. The listed devices should be used to collect, store, convert and recognize problematic situations (for example, drift, incomplete atomization, sensitivity change, etc.).
29 Reagents and materials
29.1 Copper solution, stock (1.0 ml = 1.0 mg Cu) see 20.3.
29.2 Copper solution, intermediate (1.0 ml = 10 µg Cu) see 20.4.
29.3 Copper solution, standard (1.0 ml = 0.10 µg Cu): Dilute 10.0 ml of intermediate copper solution (29.2) and 1 ml of nitric acid (HNO 3 ) (specific gravity 1.42) with water to 1 L . This standard solution is used during analysis to prepare working standard solutions.
29.4 Nitric acid (specific gravity 1.42). Concentrated nitric acid (HNO 3) (see note 4).
29.5 Argon, standard, for welding, commercially available. Nitrogen can also be used if recommended by the manufacturer.
30 Standardization
30.1 Initially turn on the instrument in accordance with the manufacturer's specifications. Follow the general instructions as specified in ASTM D 3919.
31 Testing
31.1 Clean all glassware that will be used in the preparation of standard solutions or in the processing step, or both in stages, by rinsing first with HNO 3 (1 + 1) and then with water. As an alternative, overnight soaking of glassware in HNO 3 (1 + 1) is useful in case of low detectable levels.
31.2 Measure 100.0 ml of each standard solution and mix well in a 125 ml beaker or flask.
31.3 To determine the total recoverable copper, add HNO 3 (specific gravity 1.42) to each standard solution and continue the test as described in 31.4 to 31.6. If only dissolved copper is to be detected, it is necessary to filter the sample through a 0.45 µm membrane filter before acidification, then add HNO 3 (specific gravity - 1.42) to each standard solution and then inject the sample at a rate of 5 ml/min, and then continue the test according to 31.6.
31.4 Heat the samples to 95 °C on a steam bath or hotplate in a well-ventilated fume hood until the volume is reduced to 15 ml to 20 ml without boiling (see Note 7).
31.5 Cool and filter the sample through a filter, such as a fine acid-washed cloth or ash-free filter, into a 100 ml volumetric flask. Rinse the filter two or three times with water and dilute the sample to the specified volume (see Note 16). The acid concentration in this determination should be 0.5% HNO 3 .
NOTE 16—If no suspended material is present, this filtration may be omitted, but the sample must be further diluted with water to a volume of 100 ml.
31.6 Introduce a measured amount of the sample into the oven assembly following the directions given in the manufacturer's specific instructions. Compare with ASTM D 3919.
32 Processing results
32.1 Determine the concentration of copper in each sample in accordance with ASTM D 3919.
33 Precision and bias
33.1 The precision and bias of this test method was tested on laboratory water in 16 laboratories. Thirteen laboratories also tested the method on a choice of boiler wash water, lake water, tap water, filtered water, condensate, well water, or industrial process water. In each laboratory, the results obtained by two operators were presented. Although multiple injections were performed, only one value was reported in the final protocol. Therefore, the precision of the results of a single operator could not be determined. Two sets of laboratory data were excluded from the laboratory water series and the elective water series because they were related to the determination of the laboratory level or were gross outliers. Data on limit deviation and overall precision are given in table 3.
Table 3 - Determination of tolerance limits and overall precision according to method C
|
Entered amount of Cu, µg/l |
A certain amount of Cu, µg/l |
Overall Precision S T |
Deviation ± |
Deviation 6% |
Statistical significance, 95% confidence level |
|
laboratory water |
|||||
|
Water of choice |
|||||
33.2 The data given is not applicable to water from other sources, so it is the analyst's responsibility to ensure the validity of this method in each determination (matrix).
33.3 The precision and bias of this method are in accordance with ASTM D 2777-98, which can be applied to interlaboratory testing. In accordance with the assumption of 1.4 ASTM D 2777-98, these values of precision and deviation correspond to the existing requirements for interlaboratory tests according to the methods of the Committee ASTM D 19.
34 Quality control (QC)
34.1 In order to verify the reliability and accuracy of the analytical results obtained by this method within the selected level of confidence, the following quality control (QC) procedures should be performed during the analysis.
34.2 Calibration and verification of calibration
34.2.1 Analyze at least three working standards with copper concentrations within expected limits prior to analysis of samples used to calibrate the instrument.
34.2.2 Verify the calibration of the instrument after standardization by analyzing the standard solution with a concentration of one of the standard solutions used for calibration. The absorbance must be within 4% of the absorbance at calibration. On the other hand, the concentration of the standard solution, which has the average values of the specified range, must be within ± 10% of the known concentration.
34.2.3 If the calibration cannot be confirmed (verified), recalibrate the instrument.
34.3 Initial proof of laboratory capability
34.3.1 If the laboratory has not performed the test before, or there has been a significant change in the measurement system, such as a new analyst, a new instrument, etc., a precision and deviation study is performed to demonstrate the capabilities of the laboratory.
34.3.2 Repeat the analysis of seven samples of the standard solution, prepared from the Independent Standard (Reference Material), with average values of the copper concentration of the specified range. The matrix and chemistry must match the solution used in the interlaboratory study. Each replicate series shall go through all steps of the analytical test method, including any sample retention and pre-treatment steps. Repeat analyzes can be alternated with sample analyses.
34.3.3 Calculate the mean and standard deviation of the seven results obtained and compare them with the tolerances given in Table 1. This study shall be continued until a result is obtained that meets the limits given in Table 1. If copper concentration differs from the recommended one used, for application information F And t criteria for assessing the acceptability of standard deviation and mean values should be referred to ASTM D 5847.
34.4 Laboratory control sample (LCS)
34.4.1 To validate the method, analyze the LCS containing the average concentration of copper from each batch or 10 samples. If the batch has been analyzed a large number samples, perform an LCS analysis after every 10 samples. LCSs must go through all analytical controls, including sample storage and pre-treatment. The result obtained for LCS shall be within ±15% of the certified concentration value.
34.4.2 If the result is not within these limits, the analysis of the samples must be suspended until the problem is corrected. Samples of the whole lot must be reanalyzed or the results must be qualified with an indication that they do not fall within the quality criteria of this test method.
34.5 Blank test
34.5.1 Perform a blank test on the laboratory water with each batch of tests. The copper concentration determined in the blank sample must be less than 0.5 of the minimum concentration in the calibration standard solution. If a copper concentration above this limit is detected, sample analyzes are stopped until the contamination of the system is cleared. A blank test indicates the absence or excess of contamination, or the need to take into account the results indicating that they do not meet the limits of the quality criteria of this method of determination.
34.6 Matrix additive (MS)
34.6.1 To control interference from a specific matrix test, apply MS on at least one sample of each lot by mixing the samples with a sample of known copper concentration and testing according to the procedure of the test method.
34.6.2 The additive concentration plus background copper concentration shall not exceed the maximum concentration of the calibration standard solution. The additive should provide a concentration in the sample that is 2 to 3 times the concentration of the analyte in the solution without the additive, or 10 to 50 times the detection limit of this method of determination.
34.6.3 Calculate the percent recovery of the additive R according to the following formula
Where A- concentration of the analyte in the sample containing the additive, µg/l;
V s is the volume of the sample with the additive, ml;
V- the volume of the sample used, ml;
IN is the concentration of the analyte in the sample without the additive, μg/l;
WITH is the concentration of the analyte in the additive solution, μg/l.
34.6.4 The sample additive recovery percentage shall be within specified limits based on the analyte concentration values given in ASTM D 5810, Table 1. If the recovery percentage is outside these limits, matrix interference may be present in the selected sample additive to mix. In these circumstances, one of the following measures must be taken: the interference in the matrix must be removed, all samples in the lot must be analyzed by this method regardless of whether they are subject to matrix interference, or the results are qualified indicating that they do not meet the limits of the criteria. quality of this method of determination.
NOTE 17—Allowable additive recovery values depend on the concentration of the component of interest. See also ASTM D 5810.
34.7 Duplication
34.7.1 To control the precision of the results of the analysis of the sample, analyze the sample with a duplicate of each lot. If the analyte concentration is less than five detection limits for that analyte, then a duplicate Matrix Supplement Solution (MSD) must be used.
34.7.2 Calculate the standard deviation of the duplicate values and compare them with the results of the interlaboratory comparison tests using the F-test. For information on the application of the F-criterion, see ASTM D 5847, paragraph 6.4.4.
34.7.3 If the results exceed the limits of precision, the batch of samples must be reanalyzed or the results must be qualified with an indication that they do not meet the limits of the quality criteria of this test method.
34.8 Independent reference material (IRM)
34.8.1 To verify the quantitative value obtained by this method, carry out an IRM analysis in the laboratory as a regularly used sample, if possible at least quarterly. The concentration of the analyte in the standard should be in the middle of the concentration range for the chosen method. The reproduced value obtained in the laboratory (IRM characteristic) must be within the specified error for this laboratory.
Appendix YES
(reference)
ASTM Reference Standard Compliance Information
reference national standards of the Russian Federation
(and acting as such interstate standards)
Table YES.1
|
Reference standard designation |
Compliance degree |
Designation and name of the corresponding national standard |
|
ASTM D 858 |
||
|
ASTM D 1066 |
||
|
ASTM D 1068 |
||
|
ASTM D 1129 |
||
|
ASTM D 1192 |
||
|
ASTM D 1193 |
||
|
ASTM D 1687 |
||
|
ASTM D 1691 |
||
|
ASTM D 1886 |
||
|
ASTM D 2777 |
||
|
ASTM D 3370 |
||
|
ASTM D 3557 |
||
|
ASTM D 3558 |
||
|
ASTM D 3559 |
||
|
ASTM D 3919 |
||
|
ASTM D 4841 |
||
|
ASTM D 5810 |
||
|
ASTM D 5847 |
||
|
* There is no corresponding national standard. Prior to its approval, it is recommended to use the Russian translation of this standard. The translation of this standard is in the Federal Information Fund of Technical Regulations and Standards. |
||
Keywords: atomic absorption, chelation, copper, flame, graphite furnace, water
GOST 13938.1-78
INTERSTATE STANDARD
COPPER
COPPER DETERMINATION METHODS
IPK STANDARDS PUBLISHING HOUSE
Moscow
INTERSTATE STANDARD
Introduction date 01.01.79
This International Standard specifies the gravimetric electrolytic and calculation methods for the determination of copper.
The method is based on the electrolytic extraction of copper from a solution of sulfuric and nitric acids in the presence of ammonium salts on platinum mesh electrodes at a current density of 2–3 A/dm2 and a voltage of 2.2–2.5 V.
Copper remaining in the electrolyte is determined by atomic absorption or photometric method in the form of a colored complex compound with cuprizone or lead diethyldithiocarbamate, in case of disagreement in assessing the mass fraction of copper.
With a mass fraction of copper from 99.0 to 99.9%, copper in total with silver is determined electrolytically.
The mass fraction of copper above 99.9% is determined by the difference, subtracting the sum of certain impurities from 100%.
(Changed edition, rev. No. 1, 2, 4).
1. GENERAL REQUIREMENTS
1.1.2. The mass fraction of copper is determined in parallel in three samples, impurities - in two. Simultaneously with the analysis, two control runs are performed to correct the result of the analysis for contamination of the reagents by subtracting the value of the control test from the result of determining the component in the analysis of the sample.
1.1.3. For the result of the analysis, in the electrogravimetric method for determining copper, the arithmetic mean of three parallel determinations is taken, in the calculation method for determining copper and in determining impurities in copper, the arithmetic mean of two parallel determinations.
The numerical values of the analysis results must contain the last significant digit in the same digit in which the last significant digit of the numerical value of the allowable discrepancy between the results of the determinations is located.
1.1.4. The control of the correctness of the results of the analysis is carried out according to standard samples of the composition of copper or by the method of additions.
1.2. Safety requirements for the determination of copper and impurities in copper
1.2.1. All chemical analysis operations associated with the release of toxic vapors or gases should be performed in boxes equipped with a local suction device.
Installation for electrolysis with a stirrer.
Spectrophotometer or photoelectric colorimeter with all accessories. Atomic absorption spectrophotometer, including a lamp with a hollow copper cathode, burners for an acetylene-air flame and a spray system.
Air compressor.
Drying cabinet with thermostat.
Ammonium citrate, solution; prepared as follows: 150 g citric acid dissolved in 400 cm3 of water, 200 cm3 of ammonia solution are added, cooled, topped up to 1 dm3 with water and stirred.
Disodium salt of ethylenediamine-N, N, N¢, N¢-tetraacetic acid 2-aqueous (trilon B) according to GOST 10651, 01 M solution: 37.2 g of trilon B is dissolved in 800 cm3 of water and diluted with water to 1 dm3.
Cuprizone, bis-(cyclohexanone) oxalyldihydrazone, solution 2.5 g/dm3: 2.5 g of cuprizone is dissolved with stirring in 900 cm3 of water at a temperature of 70-80°C. After cooling, the solution is filtered into a dark glass vessel, topped up with water to 1 dm3, mixed and stored in this vessel.
The solution is suitable for use within 10 days.
Sodium sulfate anhydrous according to GOST 4166.
Phenolphthalein (indicator) according to NTD, alcohol solution 1 g/dm3.
Carbon tetrachloride according to GOST 20288.
Rectified ethyl alcohol according to GOST 18300.
Copper solutions are standard.
Solution A; prepared as follows: 0.500 g of copper is dissolved in 20 cm3 of the dissolution mixture and nitrogen oxides are removed by heating. After cooling, dilute the solution with water to 100 cm3, pour it into a volumetric flask with a capacity of 1 dm3, add water to the mark and mix.
1 cm3 of solution contains 0.5 mg of copper.
Solution B; prepare as follows: 20 cm3 of solution A is placed in a volumetric flask with a capacity of 1 dm3, 5 cm3 of sulfuric acid diluted 1:1 is added, topped up to 1 dm3 with water and mixed.
1 cm3 of solution contains 0.01 mg of copper.
Paper indicator universal.
Lead (II) diethyldithiocarbamate, 0.2 g/dm3 solution in chloroform: 0.2 g of salt is placed in a volumetric flask with a capacity of 1000 cm3, 100–200 cm3 of chloroform is added and stirred until the sample is dissolved. Dilute to the mark with chloroform and mix again. The solution is stored in a dark glass bottle in a dark place.
(Changed edition, Rev. No. 2, 3, 4).
3. CONDUCTING THE ANALYSIS
3.1. Weight electrolytic method for the determination of copper (with a mass fraction of 99.0 to 99.9%)
3.1.1. A portion of copper weighing 1.0 - 2.0 g is placed on a weighing pan, where there is a weighted platinum cathode intended for electrolysis, and the total mass of the cathode and copper is determined. Separate weighing of a sample of copper and a cathode intended for electrolysis is allowed. A portion of copper is transferred to a beaker with a capacity of 250 cm3, 40 cm3 of the mixture is added for dissolution, and the beaker is covered with a watch glass. After dissolving a sample of copper, the solution is carefully heated to remove nitrogen oxides, diluted to 180 cm3 with water, heated to 40 °C, and platinum electrodes are immersed in the solution. After that, electrolysis is carried out for 2.5 hours at a current density of 2–3 A/dm2 and a voltage of 2.2–2.5 V, stirring the solution with a stirrer.
To check the completeness of copper extraction, the electrodes are immersed 5 mm below the initial position and the electrolysis is continued. In the absence of copper deposits on the freshly immersed part of the cathode, the electrolysis is considered complete.
After that, without turning off the current, they are washed with water, and then, turning off the current, they are washed with ethyl alcohol (at the rate of 10 cm3 of alcohol per one determination).
The cathode with the precipitated copper is dried at 100–105°C for 5 min, cooled in a desiccator and weighed using weights for this purpose, with which the cathode and the sample of copper were weighed.
The electrolyte and washings are poured into a volumetric flask with a capacity of 200 - 250 cm3, topped up with water to the mark and mixed. The electrolyte is retained for the determination of nickel.
Copper remaining in the electrolyte after electrolysis is determined as a colored compound with cuprizone or lead diethyldithiocarbamate by the photometric method as described in paragraphs. , .
(Revised edition, Rev. No. 4).
The pH value of the solution should be 8.5 - 9.0 The pH of the solution is checked using indicator paper.
The optical density of the solution is measured after 5 - 30 min at a wavelength of 600 nm in a cuvette with a layer thickness of 30 mm. The reference solution for optical density measurements is water. Simultaneously, two control experiments are carried out with all reagents used. The average value of the optical density of the control experiment is subtracted from the value of the optical density of the analyzed solution.
Select 0; 2.0; 4.0; 6.0; 8.0 and 10.0 cm3 of solution B in volumetric flasks with a capacity of 100 cm3, which corresponds to 0; 20; 40; 60; 80 and 100 micrograms of copper. Add 4 cm3 of a mixture of acids, 50 cm3 of water, 10 cm3 of ammonium citrate solution, 2 drops of phenolphthalein solution, ammonia solution diluted 1:4 until a faint pink color appears and 1 cm3 of excess, 10 cm3 of cuprizone solution, top up to the mark with water and mixed. The pH value of the solution should be 8.5 - 9.0.
The measurement of optical density is carried out as indicated in paragraph.
According to the found values of the optical density and the corresponding copper content, a calibration graph is built.
The solution is cooled, 10 - 20 cm3 of water is added, placed in a separating funnel with a capacity of 100 cm3 and diluted with water to a volume of 50 cm3. Add 10 cm3 of lead diethyldithiocarbamate solution and extract for 2 minutes. After separation of the layers, the extract is poured into a volumetric flask with a capacity of 25 cm3 (where 1 g of anhydrous sodium sulfate is first placed).
The extraction is repeated with 10 cm3 of the extractant. The organic layer was poured into the same volumetric flask, diluted to the mark with chloroform, and mixed.
The optical density of the solution is measured at a wavelength of 413 nm in a cuvette with optimal thickness layer. The reference solution for measuring optical density is carbon tetrachloride.
Simultaneously conduct two control experiments. To do this, 4 cm3 of the mixture for dissolution are placed in a separating funnel, topped up to 50 cm3 with water, and then proceed as indicated above. The average value of the optical density of the control experiment is subtracted from the value of the optical density of the analyzed solution.
The mass of copper is set according to the calibration graph, built as indicated in paragraph.
Place 0 into six separating funnels with a capacity of 100 cm3; 0.5; 1.0; 2.0; 3.0 and 5.0 cm3 of standard solution B. Water is added to a volume of 50 cm3 and then the analysis is carried out according to p.
Extraction and measurement of the optical density of the solution is carried out as indicated in p.
Based on the found values of optical density and the corresponding copper content, a calibration graph is built.
3.3 - 3.3.2. (Revised edition, Rev. No. 4).
3.4. Atomic absorption method for the determination of copper in electrolyte
3.4.1. Part of the electrolyte solution is placed in a glass with a capacity of 100 cm3, after rinsing it with this solution. The solution is sprayed into a flame and the flame absorbance is measured at a wavelength of 324.7 nm.
The mass of copper in the solution is set according to the calibration graph, built as indicated in p.
In volumetric flasks with a capacity of 100 cm3 take 0; 5.0; 10.0; 15.0 and 20.0 cm3 of solution B, add water to the mark and mix. Solutions contain 0; 0.5; 1.0; 1.5 and 2.0 µg/cm3 copper. The solutions are sprayed into the flame and the flame absorbance is measured at a wavelength of 324.7 nm.
Based on the found values of optical density and the corresponding copper content, a calibration graph is built.
4. PROCESSING THE RESULTS
4.1. Mass fraction of copper ( X) in percent when using electrolytic and photometric methods for determining copper is calculated by the formula
Mass fraction of copper ( X) in percent when using electrolytic and atomic absorption methods for determining copper is calculated by the formula
,
Where T- weight of the sample of copper, g;
T 1 - mass of the cathode, g;
m 2 - mass of the cathode with deposited copper, g;
m 3 - mass of copper found from the calibration curve, µg;
T 4 - mass of copper found from the calibration curve, µg/cm3;
V- volume of the analyzed electrolyte, cm3;
V 1 - volume of an aliquot part of the electrolyte, cm3.
4.2. The discrepancy between the largest and smallest results of three parallel determinations should not exceed 0.06%; between the results of two analyzes - 0.14%.
(Changed edition, Rev. No. 4).
4.3. Determination of copper (when its mass fraction is over 99.9%)
4.3.1. Mass fraction of copper ( X) as a percentage is calculated from the difference between 100 and the sum of all determined impurities according to the formula below
where is the average mass fraction of impurities identified in copper, %.
(Revised edition, Rev. No. 2).
4.3.2. The discrepancies between the results of two parallel determinations of impurities in copper should not exceed the allowable discrepancies given in the relevant standards when determining a particular impurity.
(Introduced additionally, Rev. No. 4).
APPLICATION. (Deleted, Rev. No. 4).
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of Nonferrous Metallurgy of the USSR DEVELOPERS
G.P. Giants; EAT. Fednev; A.A. Blyakhman; E.D. Shuvalov; A.N. Savelyeva
2. APPROVED AND INTRODUCED BY Decree of the State Committee for Standards of the Council of Ministers of the USSR dated 01.24.78 No. 155
3. REPLACE GOST 13938.1-68
4. The standard complies with the international standard ISO 1553-76
5. REFERENCE REGULATIONS AND TECHNICAL DOCUMENTS
|
Section number, paragraph |
Section number, paragraph |
||
GOST 13938.1-78
INTERSTATE STANDARD
COPPER
COPPER DETERMINATION METHODS
IPK STANDARDS PUBLISHING HOUSE
Moscow
INTERSTATE STANDARD
Introduction date 01.01.79
This International Standard specifies the gravimetric electrolytic and calculation methods for the determination of copper.
The method is based on the electrolytic separation of copper from a solution of sulfuric and nitric acids in the presence of ammonium salts on platinum mesh electrodes at a current density of 2–3 A/dm 2 and a voltage of 2.2–2.5 V.
Copper remaining in the electrolyte is determined by atomic absorption or photometric method in the form of a colored complex compound with cuprizone or lead diethyldithiocarbamate, in case of disagreement in assessing the mass fraction of copper.
With a mass fraction of copper from 99.0 to 99.9%, copper in total with silver is determined electrolytically.
The mass fraction of copper above 99.9% is determined by the difference, subtracting the sum of certain impurities from 100%.
(Changed edition, rev. No. 1, 2, 4).
1. GENERAL REQUIREMENTS
(Revised edition, Rev. No. 4).
The pH value of the solution should be 8.5 - 9.0 The pH of the solution is checked using indicator paper.
The optical density of the solution is measured after 5 - 30 min at a wavelength of 600 nm in a cuvette with a layer thickness of 30 mm. The reference solution for optical density measurements is water. Simultaneously, two control experiments are carried out with all reagents used. The average value of the optical density of the control experiment is subtracted from the value of the optical density of the analyzed solution.
Select 0; 2.0; 4.0; 6.0; 8.0 and 10.0 cm 3 of solution B in volumetric flasks with a capacity of 100 cm 3, which corresponds to 0; 20; 40; 60; 80 and 100 micrograms of copper. Add 4 cm 3 of a mixture of acids, 50 cm 3 of water, 10 cm 3 of ammonium citrate solution, 2 drops of phenolphthalein solution, ammonia solution diluted 1: 4, until a faint pink color appears and 1 cm 3 of excess, 10 cm 3 of cuprizone solution, Dilute to the mark with water and mix. The pH value of the solution should be 8.5 - 9.0.
The measurement of optical density is carried out as indicated in paragraph.
According to the found values of the optical density and the corresponding copper content, a calibration graph is built.
The solution is cooled, 10 - 20 cm 3 of water are added, placed in a separating funnel with a capacity of 100 cm 3 and diluted with water to a volume of 50 cm 3 . Add 10 cm 3 of lead diethyldithiocarbamate solution and extract for 2 minutes. After separation of the layers, the extract is poured into a volumetric flask with a capacity of 25 cm 3 (where 1 g of anhydrous sodium sulfate is first placed).
The extraction is repeated with 10 cm 3 of the extractant. The organic layer was poured into the same volumetric flask, diluted to the mark with chloroform, and mixed.
The optical density of the solution is measured at a wavelength of 413 nm in a cuvette with the optimum layer thickness. The reference solution for measuring optical density is carbon tetrachloride.
Simultaneously conduct two control experiments. For this, 4 cm 3 of the dissolution mixture are placed in a separating funnel, topped up to 50 cm 3 with water and then proceed as described above. The average value of the optical density of the control experiment is subtracted from the value of the optical density of the analyzed solution.
The mass of copper is set according to the calibration graph, built as indicated in paragraph.
In six separating funnels with a capacity of 100 cm 3 place 0; 0.5; 1.0; 2.0; 3.0 and 5.0 cm 3 of standard solution B. Water is added to a volume of 50 cm 3 and then the analysis is carried out according to p.
Extraction and measurement of the optical density of the solution is carried out as indicated in p.
Based on the found values of optical density and the corresponding copper content, a calibration graph is built.
3.3 - 3.3.2. (Revised edition, Rev. No. 4).
3.4. Atomic absorption method for the determination of copper in electrolyte
3.4.1. Part of the electrolyte solution is placed in a glass with a capacity of 100 cm 3, after rinsing it with this solution. The solution is sprayed into a flame and the flame absorbance is measured at a wavelength of 324.7 nm.
The mass of copper in the solution is set according to the calibration graph, built as indicated in p.
In volumetric flasks with a capacity of 100 cm 3 take 0; 5.0; 10.0; 15.0 and 20.0 cm 3 of solution B, add to the mark with water and mix. Solutions contain 0; 0.5; 1.0; 1.5 and 2.0 µg/cm 3 copper. The solutions are sprayed into the flame and the flame absorbance is measured at a wavelength of 324.7 nm.
Based on the found values of optical density and the corresponding copper content, a calibration graph is built.
4. PROCESSING THE RESULTS
4.1. Mass fraction of copper (X) in percent when using electrolytic and photometric methods for determining copper is calculated by the formula
Mass fraction of copper (X) in percent when using electrolytic and atomic absorption methods for determining copper is calculated by the formula
,
Where T- weight of the sample of copper, g;
T 1 - mass of the cathode, g;
m 2 - mass of the cathode with deposited copper, g;
m 3 is the mass of copper found from the calibration curve, μg;
T 4 - the mass of copper, found on the calibration graph, µg/cm 3 ;
V- the volume of the analyzed electrolyte, cm 3 ;
V 1 - the volume of an aliquot of the electrolyte, cm 3 .
4.2. The discrepancy between the largest and smallest results of three parallel determinations should not exceed 0.06%; between the results of two analyzes - 0.14%.
(Changed edition, Rev. No. 4).
4.3. Determination of copper (when its mass fraction is over 99.9%)
4.3.1. Mass fraction of copper (X) as a percentage is calculated from the difference between 100 and the sum of all determined impurities according to the formula below
Where - average mass fraction of impurities determined in copper, %.
