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1、INTERNATIONAL STANDARD IS0 10566 First edition 1994-l 2-l 5 Water quality - Determination of aluminium - Spectrometric method using pyrocatechol violet Qua/it the aluminium content should be below 2 pg/l. Reserve the plastics ware and optical cells, if possible, solely for aluminium determinations.
2、Re- move all residual aluminium from previous determi- nations by cleaning all plastics ware and optical cells by filling with, or soaking in, acidified water (4.3) overnight. Do not use detergent or chromic acid. 5.6 pH-metre 5.7 Microlitre pipettes, with disposable tips. 6 Sampling and samples See
3、 IS0 5667-3. Collect samples in polyethylene bottles. Clean the sample bottles and filtration device according to the procedure described in clause 5. 6.1 Filtrable aluminium Immediately after sampling, filter the sample through a membrane filter (5.2). Acidify the filtrate by adding 0,30 ml of nitr
4、ic acid (4.1) per 100 ml of sample. 6.2 Acid-soluble aluminium Add 0,30 ml of nitric acid (4.1) per 100 ml of sample. The pH shall be I,2 to 1,5, if not, add more acid. Store for at least 1 h at room temperature and filter the sample through a membrane filter (5.2). For special purposes other pretre
5、atment procedures may be used (see clause 7). NOTE 8 Failure of proper acidification of the sample leads to incorrect results because the pH during reaction and The most important interference with micro- determinations of aluminium is the release of alu- minium from the surface of the vessels used
6、for sampling and handling. In particular, aluminium is easily leached from most items of glassware. Thus, glassware shall not be used for aluminium determi- nations in the range below 50 pg/l Al. It is strongly recommended to use only plastics laboratory ware pretreated as described in clause 5. Flu
7、oride ions form stable complexes with aluminium, thus preventing the formation of the aluminium- pyrocatechol violet complex. The resulting negative bias interferes especially at low aluminium concen- trations. This effect is almost totally eliminated by the addition of magnesium ions (see 4.4) whic
8、h form relatively strong complexes with fluoride. Iron forms a coloured complex with pyrocatechol vio- let. Interference effects caused by iron are minimized by reduction to the ferrous state followed by com- plexing with 1 ,I 0-phenanthroline. This iron complex gives rise to a very small absorbance
9、 at 580 nm. 1.0 mg/l of iron is equivalent to 0,05 pg/l of alu- minium. Coloured compounds, inorganic as well as organic, that give an absorbance at 580 nm generally interfere with this determination, when absorbance exceeds 0,050 cm- . An oxidative digestion can destroy the coloured species and all
10、ow proper determination. Humic substances and other organic compounds with complexing properties can interfere. Interference is evident when addition of aluminium to the sample gives a smaller increase in absorbance than expected for that additional amount. This kind of interference is eliminated by
11、 digestion with H,O, and HNO,. 8 Procedure Depending on the cell path length and sensitivity of the spectrometer, the procedure comprises two ranges: a low level range up to 100 kg/l Al with 50 mm cells; a high level range up to 500 pg/l Al with 10 mm cells. 3 Copyright International Organization fo
12、r Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 01:39:10 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 10566:1994(E) 0 IS0 8.1 Test portions Take a test portion volume of 25 ml from sam
13、ples 6.1 or 6.2. In order to accommodate higher aluminium concentrations, use smaller test portions and adjust the volume to 25 ml by the addition of acidified water (4.3) and note the dilution factorf(see clause 91. 8.2 Calibration solutions 8.2.1 Preparation of high range calibration solutions (e.
14、g. 500 pg/l Al with 10 mm cells) Pipette 0 ml (blank), 1.00 ml, 2,00 ml, 3,00 ml, 4,00 ml and 5,00 ml respectively of the aluminium standard solution (4.8) into a series of 100 ml one- mark volumetric flasks (5.4). Make up to the mark with acidified water (4.3). These solutions contain 0 pg/l (blank
15、), 100 11911, 200 pg/l, 300 pg/l, 400 Kg/l and 500 Kg/l Al respectively. 8.2.2 Preparation of low range calibration solutions (e.g. 50 pg/i Al with 50 mm cells) Pipette, for example, 0 ml (blank), 100 PI, 200 t-11, 300 1, 400 pl and 500 1 respectively of the standard solution (4.8) into a series of
16、100 ml one-mark volumetric flasks (5.4). Make up to the mark with acidified water (4.31. These solutions contain 0 pg/l (blank), 10 pg/l, 20 Fg/l, 30 pg/l, 40 pg/l and 50 pg/l Al respectively. 8.3 Colour development Pipette each 25 ml of acidified sample (see 8.1) or calibration solutions (8.2) into
17、 100 ml plastics beakers (5.3). Add to each sample, with mixing after each addition, in the following order: I,0 ml of mixed reagent (4.4); 1,O ml of pyrocatechol violet solution (4.5); and 5.0 ml of hexamine buffer solution (4.6). Allow to react for at least 15 min, and carry out the spectrometric
18、measurement within 60 min after the start of reaction. The reaction pH of the solutions shall be in the range 5,9 + 0,l. If it is not, check for errors in preparation. 8.4 Spectrometric measurement Using the spectrometer (5.11 set up according to the manufacturer s instructions, measure the absorban
19、ce of each solution at a wavelength of 580 nm against acidified water (4.3) as a reference. Use cells of an optical path length that is appropriate for the selected range and sensitivity. Measure the blank and standard solutions with cells of the same size. Read the absorbance A, of each standard of
20、 sample. 8.5 Plotting the calibration graph Plot a calibration graph with the mass concentrations of aluminium PAI on the abscissa and the correspond- ing absorbance A, of the standards on the ordinate. The slope of the calibration curve is a measure of the sensitivity of the method, in litres per m
21、illigram. The intersection with the ordinate is the absorbance of the sample (calculated blank) without the addition of alu- minium in the standard solution. The blank and the slope shall be checked from time to time, in accordance with good analytical quality control practice, especially when new b
22、atches of re- agents are used. 8.6 Determination From the appropriate sample C(6.1) or (6.211 pipette the test portion (8.1) into a 100 ml beaker. If necess- ary, dilute the sample with acidified water (4.3) such that the mass concentration of aluminium lies within the calibration range, and record
23、the dilution factors Proceed according to 8.3 and 8.4. Choose a cell of appropriate path length. Take absorbance reading A, from the spectrometer. NOTE 9 The reaction pH normally lies within 5,9 k 0,l. If not, check that the pH of the sample is in the range of 1.2 and 1.5. Adjust the sample pH to th
24、is range using sodium hydrogen carbonate solution (4.9) or nitric acid (4.1). Make sure that the result is corrected for dilution by adjusting the pH. 9 Calculation and expression of results Taking the appropriate calibration graph for 10 mm or 50 mm optical path length, calculate the mass con- cent
25、ration of aluminium according to the following equation: PA,= (4 - 40) Xf b 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 01:39:10 MDTNo reproduction or networking permitted
26、without license from IHS -,-,- 63 IS0 where 10 Precision data PAI The following results were obtained with this method in a German round robin test in 1993. 4 A so f b is the mass concentration, in micrograms per litre, of aluminium in the sample; is the absorbance of the water sample; is the calcul
27、ated absorbance of the blank, according to 8.2; 11 Test report is the dilution factor; The test report shall include the following information: is the slope of the calibration curve, in li- tres per microgram, according to 8.2. a) b) a reference to this International Standard; Round the values of pA
28、I to the nearest 5 % of Cali- bration range, i.e. 2 pg/l in the range below 50 fig/I; cl d) 5 pg/l in the range between 50 pg/l and 200 kg/l; and IO pg/l in the range between 500 pg/l and 200 pg/l. e) precise identification of the sample; information on sample pretreatment (e.g. dis- solved aluminiu
29、m, acid-soluble aluminium etc.); the result expressed in micrograms of aluminium per litre (if necessary including information on the range of determination and precision data); any other information which may have affected the results. Type of sample True value Blank Water w/1 Iall 0 r General aver
30、age I 1 ,o 8.2 I Reproducibility standard deviation I Or8 I,6 I Repeatability standard deviation I 0.4 W3 I Number of determinations 1 136 36 Number of laboratories IS0 10566:1994(E) Synthetic Synthetic Water w/1 IQ/l Ia1 35 150 31,3 141 1 050 2,7 987 30,4 0.7 2.2 IO,0 36 36 36 9 9 9 Copyright Inter
31、national Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 01:39:10 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 10566:1994(E) Q IS0 ICS 13.060.40 Descriptors: water, qual
32、ity, water tests, chemical analysis, determlnatlon of content, aluminium, spectrometnc method. Price based on 5 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/25/2007 01:39:10 MDTNo reproduction or networking permitted without license from IHS -,-,-