GB/T 3049-1986 General method for determination of iron content in chemical products - o-phenanthroline spectrophotometric method
Some standard content:
National Standard of the People's Republic of China
General method for determining iron content in chemical products-o-Pheaanthroline spectrophotometric method
Chemical products for tndustrtal use-Generalmethod for determlnadon of iron content-o-Pheaanthroline spectrophotometric methodUDC 661.2/.6
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GB3049—B6
This standard adopts the international standard ISQ6685-B2 "Industrial chemical products-General method for determining iron content-Phenanthroline spectrophotometric method".
1 Scope of application
-1,10H
This standard specifies the general method for determining the iron content in chemical products by o-Pheaanthroline spectrophotometric method. This method is applicable to the test solution with an iron content of 10 to 500μg and a volume of no more than 60ml. The influence of the presence of other ions is shown in the appendix.
2 Principle
Use ascorbic acid to reduce the ferric iron in the test solution to ferrous iron. At pH 2-9, the ferrous iron ions can react with o-phenoline to form an orange-red complex, and its absorbance is measured at the maximum absorption wavelength of 510 nm on a spectrophotometer. This standard selects pH 4-6 to determine the complex. To eliminate the interference of certain ions, the changes in reduction and color development conditions are described in the relevant parts of the appendix. 3 Reagents and solutions
The reagents and water used in this standard, unless otherwise specified, are analytically pure reagents and distilled water or water of corresponding purity. The preparations required for the determination, unless otherwise specified, shall be prepared in accordance with the provisions of GB603-77 "Preparation Methods for Preparations and Products":
3.1 Hydrochloric acid (GB622-77): 6N and 3N solutions 3.2 Ammonia water (GB 631-77): 10% and 2.5% solutions 3.3 Sulfuric acid (GB 625-77)
3.4 Glacial acetic acid (GB 676-78);
8.5 Sodium acetate (GB 693-77);
3.6 Acetic acid-sodium acetate buffer solution: pH 4.5, 3.7 Ascorbic acid: 2% solution, the shelf life of this solution is 10! 8.8 O-phenanthroline (GB1293-77): 0.2% solution, the solution should be kept away from light, only the colorless solution can be used; 3.8 Ammonium ferric sulfate [NH,Fe(SO,)2 12H,O］,(GB 1279--77);3.10 Iron standard solution: 1 ml contains 0.100 mg iron, prepared by one of the following methods:
3.10.1 Weigh 0.863 g ammonium ferric sulfate (3.9) to 0.001 g, place in a 200 ml beaker, add 100 ml water and 10 ml sulfuric acid (3.3), transfer all to a 1000 ml volumetric flask after dissolution, dilute with water to the mark, and add a check. 3.10.2 Weigh 0.100g pure iron wire (99.9%), weigh to 0.001g, place in a 100ml beaker, add 10ml concentrated hydrochloric acid, slowly heat until completely dissolved, cool, transfer all to a 1000ml volumetric flask, dilute to scale, and shake well. 3.11 Iron standard solution: 1ml contains 0.010mg iron. Transfer 50.0ml of iron standard solution (3.10) and place in a 500ml volumetric flask, dilute to scale, and shake well. The solution is prepared before use.
4 Instruments and equipment
General laboratory instruments.
4.2 Spectrophotometer with colorimetric III of 0.5, 1 and 3cm thickness. 5 Determination Procedures
5.1 Sample Weighing and Preparation of Test Solution
The amount of sample weighing and the method of preparing test solution are specified separately in the relevant product standards. 5.2 Reagent Blank Test
When determining the volume of the test solution, use all the reagents used to prepare the test solution and the reagent blank solution prepared in the same way, dilute to the sample volume, and transfer the same volume of reagent blank solution as in the determination to conduct a blank test. 5. Drawing of the Standard Colorimetric Curve
5.3.1 Preparation of Standard Colorimetric Solution
According to the expected iron content in the test solution, add the given volume of iron standard solution (3.11) to a series of 100 ml volumetric flasks according to the range specified in the table below.
Expected iron content in the test solution, morebzxz.net
50~500
Iron standard solution
(3.11) with mother
·reagent empty" solution
5.3.2 Color development
Corresponding iron content
20 ~300
Iron standard solution
(3.11) with single
Corresponding iron content
Cuvette thickness, cm
Each container is handled in the same way as follows: Iron standard solution
(3.11) with disc
10~10%
Corresponding iron content
GB 3049-86
Add water to about 60ml, adjust the pH to about 2 with hydrochloric acid solution (3.1), check the pH with precision pH test paper, add 2.5ml ascorbic acid solution (3.7), 10ml buffer solution (3.6), 5ml o-phenanthroline solution (3.8), dilute with water to the scale, shake the hook: 5.3.3 Measurement of absorbance
Select a colorimetric solution of appropriate thickness (see the table above), at the maximum absorption wavelength (about 510nm), use water as a reference, adjust the absorbance of the spectrophotometer (4.2) to zero, and measure the absorbance. 5.3.4 Drawing of standard curve
Subtract the absorbance of each standard colorimetric solution from the absorbance of each standard colorimetric solution. The absorbance of the reagent blank test is plotted with the iron content as the horizontal axis and the corresponding absorbance as the vertical axis.
5.4 Determination
5.4.1 Color development
Take a certain amount of test solution (5.1), in which the iron content does not exceed 500μg in 60ml, and take the same volume of reagent blank solution, and place them in 100ml beakers. If necessary, add water to 60ml, adjust the pH to about 2 with hydrochloric acid solution (3.1) or water (3.2), and check the pH with precision pH test paper. Transfer all the solution to a 100ml volumetric flask and proceed as described in 5.3.2 from *Add 2.5ml ascorbic acid solution. ".
5..2 Determination of absorbance
After color development, measure the absorbance of the test solution and the reagent blank solution with water as reference according to the provisions of 5.3.3. 6 Calculation of results
Find out the iron content of the test solution and the reagent blank solution from the standard curve of 5.3.4, and calculate it according to the calculation formula of the standard related to the sample being tested.
GB 3049-86
Content of dry determination
In Appendix B, C and D, the meaning of "non-interference determination" means that the error caused by a certain ion within the limit for the determination of 20ug iron is within the range of ±5g.
GB 3049-86
Appendix B
Ions that do not interfere with determination
(Supplement)
B.1 When the test solution (5.1) contains 1000mg of the following substances, there is no interference with the determination of iron: Nat, Kt, NHt, Mg?+, Ca2+. Sr2+, Ba?+, Las+, Ce3*, A13+, Th+t, Cl-, Br1\, C1O:, C1O,, NO;, SCN-, SO, CO, Ba+ (calculated as B, O), AsO, AsOSeO, acetate, citrate, tartrate. B.2 When the test solution (5.1) contains 200mg of V5, SiO, there is no interference with the determination of iron. B.3 When the test solution (5.1) contains 500 mg PO%, Mn, there is no interference with the determination of iron. When the maximum amount is greater, the color development speed is slowed down:
B,4 When the test solution (5.1) contains 500 mg oxalate, there is no interference with the determination of iron. When the amount is greater, the color development is incomplete.
B,5 When the test solution (5.1) contains 1000 mg Pb2+, the color development speed is slowed down at a lower temperature. Keeping the temperature above 25°C does not interfere with the determination of iron.
B.6 SO\ will slowly generate yellow with o-phenanthroline during the determination. Therefore, the determination should be completed within half an hour after color development. When the test solution (5.1) contains 1000 mg S0, there is no interference with the determination of iron. B.7 When the test solution (5.1) contains 10 mg Ge*, there is no interference with the determination of iron. GE 3049-86
Attachment C:
Ions interfering with determination
(Supplement)
This appendix describes the maximum permissible limits of interfering ions in the sample solution (5.1): the method of eliminating interference, and the maximum permissible limit under the condition of adopting the method of eliminating interference. See the table below for details. f interfering ions
Maximum allowable limit, mg
Methods for eliminating interference
See Appendix D.2
See Appendix D:3
See Appendix D.4
See Appendix 1.5
See Appendix D.6
See Appendix D.7
See Appendix D.8
See Appendix D.9
See Appendix D.10
See Appendix D:4
See Appendix D.11
See Appendix D12
When eliminating interference, allowable limit is set. mg
Use hydrogen peroxide to oxidize S2~ to SO2-.
GB 3049-86
Appendix D
Operation method for eliminating interference
(Supplement)
Take a test solution (5.1) containing no more than 1000 mg of S2-, place it in a beaker, and slowly add 30% hydrogen peroxide dropwise while cooling. If the reaction is violent, continue to add after the solution cools down until the pH of the solution is close to 7 (1214 ml of 30% hydrogen peroxide is required when the content of S2- is 1000 mg). Then add 4N sulfuric acid until the pH of the solution is about 2, boil to remove excess hydrogen peroxide, cool and transfer to a 100 ml volumetric flask and operate as described in 5.3.2 starting from "add 2.5 ml of ascorbic acid solution (3.7)**." D.2 $.01
Reduction and color development are carried out under the condition of pH 6. Take a test solution (5.1) containing SO~ not more than 1000mB, place it in a 100m volumetric flask, add 10H6 acetic acid-sodium acetate buffer solution, 2.5ml ascorbic acid solution (3.7), 5ml o-pheneline solution (3.8), dilute to the mark with water, shake, and measure the absorbance (5.4.2).
Add hydrochloric acid and evaporate to dryness on a water bath to drive off nitrous acid. Take a test solution (5%1) containing NO, not more than 1000mg, cover it in a burning cup, add 10ml.6N hydrochloric acid (3.1), and stir on a water bath until dry. Dissolve it with a small amount of water, and then proceed as described in 5.4.1 from "Use hydrochloric acid (3.1) or ammonia water (3.2)." and measure the absorbance (5.4.2).
D.4 Znz+, Ce2+, Sn2+, Sa4+, Bi3+, Sh3+ and Zr4+ are shielded in the pH range of 5.8 to 6.3 using a mixed solution of disodium ethylenediaminetetraacetic acid and triammonium citrate as a masking agent to complex with interfering ions without hydrolyzing or consuming o-phenanthroline.
Take a certain amount of test solution (5.1), place it in 100 ml of water, add 2.5 ml of ascorbic acid solution (3.7), 20 ml or 40 ml of double masking agent (0.25 M disodium ethylenediaminetetraacetic acid-0.5 M triammonium citrate solution), adjust the pH to 6.8-6.3 with 10% fluoride water (3.2), transfer all the solution into a 100 ml volumetric flask, add 5 ml of o-phenanthroline solution (3.8), dilute with water until thick, and spread evenly. Place for 30 minutes and measure the absorbance (5.4.2)
Use 20ml double masking agent to eliminate the interference of 500mgSn2+, Sn4+, Bi 3+, S3+, 200mgZn2*, 400mgCdz+, 60mgZr4+.
Use 40ml double masking agent to eliminate the interference of 500mgZn2+, Cd2+ or 175ngZr1+. D: $MnO.
Use hydroxylamine hydrochloride instead of ascorbic acid as reducing agent. When there is less than 500mg of MnO, it will not interfere with the determination. Take the test solution (5.1) containing no more than 500mg of MnO, place it in a 100ml beaker, add water to about 40ml, add 5ml6N hydrochloric acid (3.1), add 10% hydroxylamine hydrochloride solution until it is colorless, and add 1.ml excess. Leave for 15 minutes, adjust the pH to about 2 with aliquots of water (3.2), transfer all the solution into a 100 ml volumetric flask, and proceed as described in 5.3.2 starting from "add 10 ml of buffer solution (3.6)", absorbance (5.4.2).
While measuring the absorbance of the test solution and the reagent blank solution, measure the absorbance of the sample blank solution. The sample blank is the same composition as the test solution, but without the addition of phenanthroline solution (3.8). The absorbance of the test solution minus the absorbance of the reagent blank solution and the sample blank solution is the measurement result.
GB 3049-86
Heating to 50-60℃ can hydrolyze P,01 to PO1. Take a test solution (5.1) containing no more than 500mg of P,0, place it in a 100mg beaker, add water to about 40ml, adjust the pH to about 2 with hydrochloric acid (3.1) or ammonia water (3.2), add 2.5ml ascorbic acid solution (3.7) and 10ml buffer solution (3.6), heat to 50-60℃ on a water bath, add 5ml o-phenanthroline solution (3.8), and cool to room temperature. Transfer all the solution to a 100ml volumetric flask, dilute to the mark with water, and shake the spoon. Measure the absorbance (5.4.2). D.7 F-
Adding boric acid to an acidic solution and heating it to 50-60℃ can destroy the complex between F- and Fe+ and Fe2+, thereby eliminating the interference of F-.
Take a test solution (5.1) containing no more than 500 mg of F-, place it in a 100 ml beaker, add water to about 40 ml, adjust the pH to about 2 with hydrochloric acid (3.1) or ammonia water (3.2), add 20 ml of saturated acid solution, heat to 50-60 ° C on a water bath, add 2.5 ml of ascorbic acid solution (3.7), 10 ml of buffer solution (3.6), 5 ml of o-phenanthroline solution (3.8), and cool to room temperature. Transfer all the solution to a 100 ml volumetric flask, dilute with water to degrees, and shake well. Measure the absorbance (5.4.2). D.. WO2- and Mo0:
In the presence of sufficient amount of tartaric acid, when pH is above 3.2, the interference of WO- (or Mo0) can be eliminated. Take a test solution (5.1) containing no more than 500 mg of W02~ (or Mo0~), place it in a 100 ml beaker, add water to about 40 ml, add 20 ml of 1M tartaric acid solution, adjust the pH to 4-5 with 2M sodium hydroxide solution, add 2.5 ml of ascorbic acid solution (3.7), 10 ml of buffer solution (3.6), 5 ml of o-phenanthroline solution (3.8), and transfer all the solution to a 100 ml volumetric flask; dilute with water to the scale and shake well. After standing for 30 minutes, measure the absorbance (5.4.2). D.9 Cr3+, Ni2+, Co2+ and Cu2+
Extract iron with 4-methylpentyl-［2］ at a concentration of about 6N hydrochloric acid, and then back-extract with water for color development. Take a test solution (5.1) containing no more than 500 mg of Cr3+ (or Nt2+, Co2+ and Cu2+), place it in a 125 ml separatory funnel, add water to about 40 ml, add 40 ml of hydrochloric acid, 10 ml of 4-methylpentanone-【2.], shake for 1 min, let it stand and discard the aqueous phase. Add 20 ml of water to the separatory funnel, shake for 1 min, let it stand. Transfer the aqueous phase to a 100 ml volumetric flask, add 5 ml of water to the separatory funnel, shake for 30 seconds, let it stand. Transfer the aqueous phase to the same volumetric flask, and perform the following operations as described in 5.3.2 starting with adding 2.5 ml of ascorbic acid solution (3.7)...\, and measure the absorbance (5.4.2). D,10 T14*
In the presence of sufficient tartaric acid, tartaric acid and Ti4+ complex in the pH range of 3.2 to 5.3, which can prevent Ti4- from hydrolyzing and weaken the formation of Ti1- and ascorbic acid or orange complexes, so that it does not interfere with the determination. Take a test solution (5.1) containing no more than 150mg of Ti4-, place it in a 100ml beaker, add water to about 30ml, add 20ml of 1M tartaric acid solution, adjust the pH to about 4 with ammonia water (3.2), add 2.5ml of ascorbic acid solution (3.7), 10ml of buffer solution (3.6), and 5ml of o-phenanthroline solution (3.8). Transfer all the solution into a 100ml volumetric flask, add water to the scale, and shake well. Measure the absorbance (5.4.2). While measuring the absorbance of the test solution and the reagent whitening solution, measure the absorbance of the sample blank solution. The sample blank is the solution that is separated from the test solution but without the addition of o-phenanthroline solution (3.8). The absorbance of the test solution minus the absorbance of the reagent blank and the sample blank is the test result.
Use sodium chloride solution to precipitate Ag- as silver nitride, and then add sodium thiosulfate solution to dissolve the complex so that it does not interfere with the determination. GB 3049 86
Take a test solution (5.8) containing no more than 150 mg of Ag.1), place it in a 100ml beaker, add water to about 30ml, add a sufficient amount of 1% sodium chloride solution, and precipitate the Ag. Use hydrochloric acid (3.1) or ammonia ash (3.2) to adjust the pH to 3~5, add 2.5ml ascorbic acid solution (3.7), 10ml buffer solution (3.6), dropwise add 4% sodium thiocarbonate solution until the precipitate is just dissolved, add 5ml o-Phylline solution (3.8). Transfer all the solution into a 100ml volumetric flask, dilute to volume with water, and shake well. Measure the absorbance (5.4.2). If flooding occurs, filter and measure the absorbance of the clear liquid D.12 Hg* and Hg 2
Hgz (or Hg) and o-phenylene glycol to form a colorless complex, which consumes the color developer. Therefore, In addition to the specified amount, an additional 5ml of 0;2% phenanthroline solution should be added for every 5mgHgz (or Hg2). Take the test solution (5.1) containing no more than 40mg of Hg (or Hg*), place it in a 100ml volumetric flask, and use 1N Adjust the pH to about 2 with nitric acid, add 2.5 ml of ascorbic acid solution (3.7), 10 ml of buffer solution (3.6), add phenylaline solution (3.8) according to the calculated amount, dilute to the mark with water, and shake the hook to measure the absorbance (5.4. 2). If confusion occurs, F filter and measure the absorbance of the clear liquid GB3049-86
| Aluminum trichloride, zinc sulfate and sodium nitrate were verified in eight laboratories. Each sample was used to prepare three different concentrations of test solutions. 20ml of each concentration of test solution was taken for 5 measurements. , the following table lists the statistical results. Test name
Calculation items
Average, μgFe/ml
Indoor relative standard deviation, %
Inter-room relative standard deviation , %
Note; the relative standard deviation is;
Additional notes:
aluminum trichloride
standard deviation
average value||tt| |·Sodium Nitrate
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of the Tianjin Research Institute of Chemical Industry of the Ministry of Chemical Industry. This standard is drafted by Yang Chengyin, the main drafter of this standard. Liu Shuying 3.
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