SANS 11083-2005 Water quality - Determination of chromium (VI) - Spectrometric method using 1 5-diphenylcarbazide《水质-铬(VI)测定 采用1 5-二苯卡巴肼的光谱法》.pdf

1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA

2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ICS 13.060.50 ISBN 0-626-17442-2 SANS 11083:2005Edition 1ISO 11083:1994Edition 1 SOUTH AFRICAN NATIONAL STANDARD Water quality Determination of chromium(

4、VI) Spectrometric method using 1,5-diphenylcarbazide This national standard is the identical implementation of ISO 11083:1994 and is adopted with the permission of the International Organization for Standardization. Published by Standards South Africa 1 dr lategan road groenkloof private bag x191 pr

5、etoria 0001 tel: 012 428 7911 fax: 012 344 1568 international code + 27 12 www.stansa.co.za Standards South Africa SANS 11083:2005 Edition 1 ISO 11083:1994 Edition 1 Table of changes Change No. Date Scope Abstract Specifies a spectrometric method for determination of chromium(VI) in water. The metho

6、d is applicable to the determination of dissolved chromium(VI) in the concentration range of 0,05 mg/L to 3 mg/L. The application range may be extended by dilution of the sample. Keywords chemical analysis and testing, chromium, determination of content, quality, spectrometric method, water, water t

7、ests. National foreword This South African standard was approved by National Committee StanSA SC 5140.19A, Water Water sampling and analysis, in accordance with procedures of Standards South Africa, in compliance with annex 3 of the WTO/TBT agreement. This SANS edition cancels and replaces SANS 5206

8、 (SABS SM 206:1975). INTERNATIONAL STANDARD ISO 11083 First edition 1994-08-15 Water quality - Determination of chromium(Vl) - Spectrometric method using 1 ,!Gdiphenylcarbazide Qual26 de Ieau - Dosage du chrome(VI) - Methode par spectrom 8,0. it shall be between 7,5 and If the pH is outside this hyd

9、roxide Solution (3.2) or (3.3), accordingly. range, adju st with sodiu m PhosP horic acid sol ution A Add 1 ml of aluminium su fate Solution (3.5) and mix. Check the pH; it shall be between 7,0 and 7,2. If the pH is outside this range, adjust with phosphor acid Solution A (3.3). Allow the precipitat

10、e to settle for at least 2 h. Deca the supernatant and filter 200 ml through membrane filter (4.2) discarding the first 50 ml OT filtrate. 3.13 Sodium chloride, NaCI. 5.2 Samples in the pr reducing substances esence of oxidizing or 4 Apparatus Ordinary laboratory apparatus and 4.1 Photometer or spec

11、trometer, equipped with cells of Optical path lengths between 10 mm and 50 mm. 4.2 Membrane filtration device, equipped with membrane filters with a pore size of 0,4 Fm to 0,45 Pm. 43 . pH-measuring equipment. 4.4 Gas flow control. Collect a 1 000 ml Sample in a glass bottle, add 10 ml of buffer Sol

12、ution (3.1) and mix. Measure the pH using the equipment (4.3); it shall be between - - /,5 and 80 I * If the pH is outside this range, adjust with hydroxide Solution (3.2) or phosphoric acid so (3.3) accordingly. sodium ution A Add 1 ml of aluminium sulfate Solution (3.5) 2 nd mix. Check the pH; it

13、shall be between 7,0 and 7,2. If the pH is outside this range, adjust with phosphoric acid Solution A (3.3). Add 1 ml of sulfite Solution (3.6) checking for an excess of sulfite using sulfite test Paper (3.7). If there is no excess of sulfite, add more sulfite Solution until an excess is obtained. 2

14、 0 ISO ISO 11083:1994(E) Allow the precipitate to settle for at least 2 h. Decant the supernatant and filter 200 ml through a membrane filter (4.2) discarding the first 50 ml of filtrate. 7 Procedure 7.1 Procedure in the absence of oxidizing or reducing substances 6 Interferences In the presence of

15、lead, barium and silver ions (salts), chromates of low solubility may be formed and the chromium(Vl) contained in them will not be determined. Hexavalent molybdenum and mercury salts also form a yellow or blue colour respectively with the reagent, but the intensities are much lower than for chromium

16、(VI). Iron(lll) forms a yellow colour at concentrations above 1 mg/l and vanadium forms a yellow colour that fades. Chromium(lII) and other interfering metal ions are precipitated in a Phosphate-buffered Solution using aluminium sulfate as a precipitation aid and are removed by filtration. Transfer

17、50 ml (volume V) of the filtrate (5.1) to a 100 ml volumetric flask. Add 2 ml of phosphoric acid Solution B (3.4) and 2 ml of diphenylcarbazide Solution (3.8) and dilute to 100 ml with water. Measure the absorbance after 5 min to 15 min at a wavelength between 540 nm and 550 nm using water in the re

18、ference cell (absorbance A,), and cells with an Optical path length of 40 mm or 50 mm for concentrations below 0,5 mg/l, and of 10 mm for concentrations between 0,5 mg/l and 3 mg/l. If the concentration is higher than 3 mg/l, repeat the determination, using a smaller aliquot of the filtrate (volume

19、V). For the blank value, carry out a blank test in parallel with the determination using water in place of the Sample (absorbance Ab). Valency changes of chromium due to the presence of NOTE 2 This blank does not take into account the oxidizing or reducing substances tan be avoided by chromium conte

20、nt of the precipitation reagents, which has using the following pretreatment Steps. been found to be negligible. Oxidizing substances are reduced by the addition of sulfite to the neutralized Sample; chromium(VI) will not react under these conditions. Excess sulfite and other reducing substances are

21、 then oxidized with hypochlorite. Excess hypochlorite and any chloro- amines formed are destroyed in the acid Solution by the addition of sodium chloride and the chlorine formed is purged with air. If the measured blank disagrees significantly with the blank from the calibration function (7.3), chec

22、k the latter. If the filtrate is coloured or turbid, take another aliquot and treat it as described in this subclause, omitting the 1,5-diphenylcarbazide Solution. Use the absorb- ante measured as a colour correction (absorbance At). In spite of this pretreatment of the Sample, slow reduction of chr

23、omium(Vl) may occur in some waters. Leachate from landfills, raw domestic waste water and certain waste waters from Chemical plants will show losses of chromium(VI) after several hours. lt is therefore essential that these samples be analysed as soon as possible after collection. 7.2 Procedure in th

24、e presence of oxidizing or Ammonia nitrogen does not interfere in concen- trations below 500 mg/l, but amine compounds may be transformed by hypochlorite into chloroamines, which are not always decomposed by the addition of chloride. This interference is indicated by the appearance of a yellow or br

25、ownish colour on addition of 1,5-diphenylcarbazide. reducing substances Transfer 50 ml (volume V) of the filtrate (5.2) to a 100 ml volumetric flask. Add 1 ml of sodium hypochlorite Solution (3.9) after checking for 1 min for excess chlorine using the potassium iodide starch test Paper (3.10). Nitri

26、te nitrogen interferes with the formation of the red violet chromium(VI)-1,5-diphenylcarbazone complex in concentrations exceeding 20 mg/l. If there is no excess chlorine, add more sodium hypochlorite Solution (3.9) until an excess is obtained. Add 2 ml of phosphoric acid Solution B (3.4) dissolve 1

27、0 g of sodium chloride (3.13) in the Sample, and pass air through the Sample with a flow rate of approxi- mately 40 I/h for 40 min. Perform this procedure in a fume chamber. Add 2 ml of 1,5-diphenylcarbazide Solution (3.8) and dilute to 100 ml with water. Vanadium in excess of 4 mg/l, and molybdenum

28、 and mercury each in excess of 200 mg/1 may interfere. Measure the absorbance after 5 min to 15 min at a wavelength between 540 nm and 550 nm using 3 ISO 11083:1994(E) 0 ISO water in the reference cell (absorbance A,) and cells with an Optical path length of 40 mm or 50 mm for concentrations below 0

29、,5 mg/l, and of 10 mm for concentrations between 0,5 mg/l and 3 mg/l. If the concentration is higher than 3 mg/l, repeat the determination, using a smaller aliquot of the filtrate (volume V). For the blank value, repeat the procedure, using water in place of the filtrate (absorbance Ab). NOTE 3 This

30、 blank does not take into account the chromium content of the precipitation reagents, which has been found to be negligible. If the measured blank disagrees significantly with the blank from the calibration function (7.3), check the latter. If the filtrate is coloured or turbid, take another aliquot

31、 and treat it as described in this subclause, omitting the 1,5-diphenylcarbazide Solution. Use the absorb- ante measured as colour correction (absorbance At). 7.3 Calibration Pipette, for example, 0 ml; 0,5 ml; 1,O ml; 2,0 ml; 3,0 ml; 4,0 ml and 5,0 ml of chromium(Vl) Standard Solution (3.12) into a

32、 series of 100 ml volumetric flasks. Dilute each to approximately 40 ml with water, add 2 ml of phosphoric acid Solution B (3.4) and 2 ml of 1,5-diphenylcarbazide Solution (3.8) and dilute to 100 ml with water. These calibration solutions have concentrations of 0 mg/l; 0,025 mg/l; 0,05 mg/l; 0,lO mg

33、/l; 0,15 mg/l; 0,20 mg/l and 0,25 mg/1 of chromium(Vl) respectively. Measure the absorbance after 5 min to 15 min at a wavelength between 540 nm and 550 nm (absorb- ante A,) in cells with an Optical path length of 40 mm or 50 mm using water in the reference cell. The wavelength used shall be the Sam

34、e for the calibration and the measurement. Plot the mass concentration of chromium(Vl) against the absorbance values to establish the calibration graph. Alternatively, calculate the calibration graph by regression analysis. The slope of the calibration graph is a measure of the sensitivity of the me

35、thod. The Ordinate intercept is the blank. Check both the slope of the graph and the blank regularly, especially when new batches of reagents are used. For calibration of other concentration ranges, proceed in the Same way using different calibration solutions. Fo r the high concentration range, OP

36、tical p ath length of IO mm. use cells with an Establish separate calibration functions for cells with different Optical path lengths. 8 Expression of results 8.1 Calculation Calculate the mass concentration of chromium(VI), f-(v), in milligrams per litre, using the equation .fcA, -Ab) P(CrVI) = /,

37、or PKNI) = * f CA s -A, -Ab 11 (if a correction has been made for coloured and turbid solutions) where AS is the absorbance of the Sample; Ab is the absorbance of the blank; At is the absorbance of the correction Solution; .f is the dilution factor (for V = 50 ml it is 2; if other aliquots are taken

38、 it is 1 OO/V); is the sensitivity (slope of the calibration graph). Report the results to the nearest tenth of a milligram, if they exceed IO mg/l, and to the nearest hundredth of a milligram, if they are below IO mg/l. 0 ISO ISO 11083:1994(E) 8.2 Precision and accuracy An interlaboratory trial, ca

39、rried out in Germany F.R. in 1986, produced the results given in table 1. Table 1 - Precision data I 11 0 Matrix 1, .Y .Y Of vc, qq VCR WFR % mg/1 mg/1 mg/1 % mg/l % % Surface water 15 58 14 19,4 0,072 0,067 0,002 3,3 0,004 5,5 93,2 Domestic effluent sewage 18 71 1 19 0,180 0,166 0,002 1,4 0,012 6,9

40、 92,l Treated effluent (pickling factory) 18 72 0 0,O 0,630 0,543 0,021 3,9 0,107 19,7 86,l Treated effluent (galvanic factory) 17 67 5 69 1,180 1,112 0,020 1,8 0,088 7,9 94,2 I is the number of Iaboratories n is the number of values 0 is the numbers of outliers Iza is the percentage of outliers x i

41、s the true value x is the mean value ar is the repeatability Standard deviation vcr is the repeatability Variation coefficient GR is the reproducibility Standard deviation VCR is the reproducibility Variation coefficient WFR is the recovery rate 9 Test report The test report shall include the follow

42、ing information: a) a reference to this International Standard; b) all information necessary for the complete identification of the Sample; d details of Sample pretreatment, if applicable; d) the wavelength at which the measurements were made; e) the results and the method of expression used; details of any operations not included in this International Standard, or regarded as optional, and any other circumstances that may have affected the results. 5 Standards South AfricaThis s tandard may only be used and printed by approved subscription and freemailing clients of the SABS .