1、BRITISH STANDARD BS 6068-2.2: 1983 ISO 6332:1982 Water quality Part 2: Physical, chemical and biochemical methods Section 2.2 Determination of iron: 1, 10-phenanthroline photometric method ISO title: Water analysis Determination of iron 1, 10-phenanthroline photometric method UDC 556:614.777:628.1/.
2、3:663.63:543.42.062:546.72BS6068-2.2:1983 This British Standard, having been prepared under the directionof the Environment andPollution Standards Committee, was published underthe authorityof the BoardofBSI andcomes intoeffecton 30September 1983 BSI 10-1999 The following BSI references relate to th
3、e work on this standard: Committee reference EPC/44 Draft for comment 81/52275 DC ISBN 0 580 11998 X Amendments issued since publication Amd. No. Date of issue CommentsBS6068-2.2:1983 BSI 10-1999 i Contents Page National foreword ii 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Re
4、agents 1 5 Apparatus 1 6 Sampling and preparation of test samples 2 7 Procedure 2 8 Expression of results 3 9 Precision 3 10 Interferences 4 11 Test report 5 Table Statistical data on the repeatability of the method 4 Publications referred to Inside back coverBS6068-2.2:1983 ii BSI 10-1999 National
5、foreword This Section of this British Standard, which has been prepared under the direction of the Environment and Pollution Standards Committee, is identicalwith ISO 6332:1982 “Water analysis Determination of iron 1, 10-phenanthroline photometric method”. The International Standard was prepared by
6、subcommittee 2, Physical, chemical and biochemical methods, of Technical Committee 147, Water quality, of the International Organization for Standardization (ISO) as a result of discussion in which the UK participated. This British Standard is being published in a series of Parts subdivided into Sec
7、tions that will generally correspond to particular International Standards. Sections are being, or will be, published in the following Parts. Part 0: Introduction; Part 1: Glossary; Part 2: Physical, chemical and biochemical methods; Part 3: Radiological methods; Part 4: Microbiological methods; Par
8、t 5: Biological methods; Part 6: Sampling. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; atten
9、tion is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Briti
10、sh Standard”. Additional information. 1) Attention is drawn to the general method for determination of iron by a 1,10-phenanthroline spectrophotometric method, published as BS 6337-3. 2) Attention is drawn to the need to take into account the dilution factor of5 when calculating results when the pro
11、cedure given in7.2.1.2 has been carried out. 3) The following clarification of the instructions in clause7 for taking test portions and test samples should be noted: a) in line 2 of7.1, “(clause 6)”, should be read as “(6.2, 6.3 or 6.4, as appropriate)”; b) in line 2 of7.2.1, “appropriate” should be
12、 read before “test portion”; c) in line 1 of7.2.2, “appropriate” should be read before “test sample” and “either 6.2 or 6.3” should be read as “7.1”; d) in line 1 of7.2.3, “appropriate” should be read before “test portion”. Cross-reference International Standard Corresponding British Standard ISO 56
13、67-1:1980 BS 6068 Water quality Section 6.1:1981 Guidance on the design of sampling programmes (Identical)BS6068-2.2:1983 BSI 10-1999 iii A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct applicatio
14、n. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and ma
15、y have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS6068-2.2:1983 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a1,10-phenanthroline photometric method for the determination of iron in water and
16、waste water. Procedures are described for the determination of total iron, total acid soluble iron, total dissolved iron and, if required, acid soluble and dissolved iron(II) and iron(III). The method is applicable to the determination of iron concentrations between 0,01 and 5mg/l. Iron concentratio
17、ns above 5mg/l may be determined after suitable dilution of the sample. 2 Reference ISO 5667-1, Water quality Sampling Part1:Guidance on the design of sampling programmes. 3 Principle 1) Addition of 1,10-phenanthroline solution to a testportion and photometric measurement of the orange-red complex a
18、t a wavelength of about510nm. If determining total iron, total acid soluble iron and total dissolved iron, hydroxylammonium chloride is added to reduce iron(III) to iron(II). If undissolved iron, iron oxides or iron complexes are present, pretreatment is necessary to bring such compounds into soluti
19、on. The iron(II)-1,10-phenanthroline complex is stable in the pH range from 2,5 to 9 and the intensity of the colour is proportional to the amount of iron(II) present. The relationship between concentration and absorbance is linear up to a concentration of5,0mg of iron per litre. Maximum absorbance
20、occurs at about 510nm molar absorption coefficient11 10 3l/(molcm). 4 Reagents Use only reagents of recognized analytical grade. The water used shall have as low an iron concentration as possible; a measurable iron concentration in the reagents is permissible provided that the lowest concentration t
21、o be determined is at least three times the standard deviation of the predetermined results of blank tests. Deionized water or water distilled from an all-glass apparatus has been found to be suitable. 4.1 Acetate buffer Dissolve 40g of ammonium acetate (CH 3 COONH 4 ) and 50ml of glacial acetic aci
22、d (CH 3 COOH) ( =1,06 g/ml) in water and dilute to 100ml with water. 4.2 Di-isopropyl ether (CH 3 ) 2 CH O CH(CH 3 ) 2 . ( = 0,72g/ml), alcohol free, boiling point between67 and 69 C. 4.3 Hydrochloric acid solution, = 1,125g/ml, c(HCl) . 7,7mol/l. 4.4 Hydroxylammonium chloride, 100g/l solution. Diss
23、olve 10g of hydroxylammonium chloride (NH 2 OHHCl) in water and dilute to 100ml. This solution is stable for at least 1week. 4.5 Nitric acid, concentrated, = 1,40g/ml. 4.6 1,10-phenanthroline solution Dissolve 0,5g of 1,10-phenanthrolinium chloride (monohydrate) (C 12 H 9 ClN 2 H 2 O) in water and d
24、ilute to 100ml. Alternatively, dissolve 0,42g 1,10-phenanthroline monohydrate (C 12 H 8 N 2 H 2 O) in 100ml of water containing 2 drops of hydrochloric acid(3.3). This solution is stable for 1 week if stored in the dark. 4.7 Potassium peroxodisulphate, 40g/l solution. Dissolve 4g of potassium peroxo
25、disulphate (K 2 S 2 O 8 ) in water and dilute to 100ml. This solution is stable for several weeks if stored at room temperature in a dark glass bottle. 4.8 Iron, standard solution corresponding to 0,10g of iron per litre. Weigh 50,0mg of iron wire (purity 99,99%) into a500ml volumetric flask. Add 20
26、ml of water, 5ml of the hydrochloric acid solution (4.3), and warm gently to dissolve. Cool, and make up to the mark with water. 1ml of this standard solution contains 0,10mg of iron. This solution is stable for at least 1 month if stored in a resistant glass or plastics bottle. Commercial iron stan
27、dard solutions may be used. 4.9 Sulphuric acid, = 1,84g/ml. 4.10 Sulphuric acid solution, c(1/2 H 2 SO 4 ) . 4,5 mol/l. Add slowly and with vigorous stirring 1 volume of concentrated sulphuric acid (4.9) to 3 volumes of water while cooling. 5 Apparatus All glassware, including sample containers, sha
28、ll be washed with hydrochloric acid and rinsed with water before use. 1) For possible sources of interference and methods for their removal, see7.2.1.2 and clause10.BS6068-2.2:1983 2 BSI 10-1999 Usual laboratory equipment, and 5.1 Spectrophotometer, prism or grating type, suitable for making measure
29、ments at 510nm; or photoelectric absorptiometer, fitted with a narrow band pass optical filter having maximum transmission in the region of 510nm. 5.2 Photometric cells, of optical path length at least10mm and appropriate to the expected absorbance of the test solution. NOTECells of longer optical p
30、ath length are preferable for determining iron concentrations less than 1,0mg/l. 5.3 Membrane filter, average pore size 0,454m. 6 Sampling and preparation of test samples WARNING Appropriate safety precautions shall be taken when acidifying samples due to the possibility of release of toxic gases. 6
31、.1 Sample Take the sample in accordance with ISO 5667-1 and any specific recommendations for the type of water under examination. Appropriate containers such as polyethylene shall be used. 6.2 Total iron Acidify the sample immediately after collection to pH1. In general, 1ml of concentrated sulphuri
32、c acid (4.9) is sufficient for 100ml of sample. If necessary, adjust the pH by addition of dilute sulphuric acid (4.10) and take into account any dilution in the final calculations. 6.3 Total acid soluble iron and acid soluble iron(II) Filter the acidified sample (6.2) through the membrane filter (5
33、.3). If it is intended to determine iron(II), this filtration should be carried out under an inert atmosphere, for example nitrogen or carbon dioxide, in order to exclude as much air as possible and thus to prevent oxidation of the iron(II). Fill a glass sample bottle with the filtrate and continue
34、until at least five times the volume has overflowed. Immediately close the bottle with a tightly fitting glass stopper. 6.4 Total dissolved iron To separate dissolved iron from undissolved iron, filter the sample (6.1) immediately after collection through a membrane filter (5.3) and then acidify to
35、pH 1 (see6.2). 7 Procedure 7.1 Test portion Take, as the test portion, 50,0ml of the acidified test sample (clause6). 7.2 Preparation of test solution 7.2.1 Total iron If undissolved iron, iron oxides or iron complexes are present transfer the test portion (7.1) to a 100ml boiling flask and carry ou
36、t the following pretreatment. 7.2.1.1 Oxidation Add 5ml of potassium peroxodisulphate solution(4.7) and gently boil for about 40min ensuring that the volume does not fall below about20ml. Then cool and transfer it to a one-mark volumetric flask of capacity 50ml and make up to the mark with water. NO
37、TEAlternatively, the mixture may be autoclaved in a100ml closed bottle for 30min, then cooled and diluted to100ml. This dilution should be taken into account in calculating the result by multiplying by a factor of 2. If the solution is turbid after oxidation and before dilution, filter it immediatel
38、y through the membrane filter (5.3) into the volumetric flask. Rinse the filter with a small amount of water adding the washings to the filtrate and make up to the mark with water. 7.2.1.2 Removal of interferences If removal of interferences is necessary (seeclause10) proceed as follows: Transfer ex
39、actly 10ml of the oxidized solution(7.2.1.1) to a 100ml separating funnel and add 15ml of hydrochloric acid solution (4.3). Cool and extract three times with 25, 10 and 10ml portions respectively of di-isopropyl ether (4.2). Combine the ether phases in a second separating funnel and extract twice wi
40、th 25 and 10ml portions respectively of water. Combine the aqueous extracts and heat cautiously to remove residual ether. Cool, add 0,5 ml of sulphuric acid (4.10) and dilute to50ml with water. 7.2.1.3 Reduction to iron(II) Transfer the whole of the solution from 7.2.1.1 or7.2.1.2 to a 100ml flask a
41、nd add 1ml of hydroxylammonium chloride solution (4.4) and mix thoroughly. Then add 2ml of acetate buffer (4.1) to bring the pH to between 3,5 and 5,5, preferably 4,5. NOTEThe reduction of iron(III) to iron(II) proceeds most effectively at pH 1. The buffer solution should therefore be added last.BS6
42、068-2.2:1983 BSI 10-1999 3 7.2.2 Total acid soluble iron and total dissolved iron Treat the test sample from either 6.2 or 6.3 according to the procedure described in7.2.1. If the sample is known to contain only iron in the form of iron(III) the oxidation step may be omitted. 7.2.3 Acid soluble iron
43、(II) and dissolved iron(II) Transfer the test portion (7.1) to a 100ml flask, add2ml of acetate buffer and mix thoroughly. The pH of the mixture should be between 3,5 and 5,5, preferably 4,5. 7.2.4 Acid soluble iron(III) and dissolved iron(III) The concentration of acid soluble iron(III) or dissolve
44、d iron(III) is derived from the difference between the appropriate concentration of iron determined in7.2.2 and the appropriate concentration of iron(II) determined in7.2.3. 7.3 Blank test Prepare a blank test solution using exactly the sameprocedure as for the test sample, but replacing the 50ml of
45、 test portion with 50ml of water. 7.4 Calibration 7.4.1 Preparation of reference solutions Prepare a series of iron reference solutions to cover a range of concentrations appropriate to the expected iron concentration of the test sample by transferring appropriate accurately known volumes of the iro
46、n standard solution (4.8) to a series of one mark volumetric flasks each of capacity 50ml. Add 0,5ml of dilute sulphuric acid (4.10) to each flask and make up to the mark with water. Treat a series of iron reference solutions in a similar fashion to the test solutions, according to the appropriate p
47、rocedure for each form of iron to be determined (see7.2). 7.4.2 Formation of the absorbing compound Add 2ml of 1,10-phenanthroline solution (4.6) to each solution (7.4.1) and place them in the dark for15min. 7.4.3 Photometric measurements Measure the absorbance of the solutions from7.4.2 using the s
48、pectrophotometer or the absorptiometer(5.1) at 510nm using water in the reference cell. 7.4.4 Plotting the calibration graphs For each series of calibration solutions prepare a calibration graph by plotting the iron concentration of the test solution in milligrams per litre as abscissae against the
49、corresponding measured absorbance as ordinate. A separate calibration curve is required for each form of iron, for each photometric instrument and for each optical path length of cell. 7.4.5 Frequency of calibration Check the calibration periodically and especially for each new batch of reagents. 7.5 Determination 7.5.1 Formation of the absorbing compound To both the test solution (7.2) and the blank test solution (7.3), add 2ml of 1,10-phenanthroline solution (4.6) and place in the dark for 15min. 7.5.2 Photometric measu
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