1、UDC 669.1 : 669.14 : 620.1 : 546.76 : 543.422 DEUTSCHE NORM April 1990 Chemical analysis of ferrous materials Determination of chromium in steels and iron Flame atomic absorption spectrometric method DIN - EN 10188 European Standard EN 10 188 : 1989 has the status of a DIN Standard. National forewor
2、d This standard has been created by the adoption of EURONORM 188 as a European Standard. The responsible German body involved in the preparation of this standard was the Normenausschu Eisen und Stahl (Steel and Iron Standards Committee). Standards referred to See References. International Patent Cla
3、ssification G O1 N 21/71 G O1 N 33/20 Editors note In the preparation of the English version of DIN EN 10 188, the following point has been noted which may be in need of correction in subsequent editions of the standard. The responsible CEN Secretariat will be advised accordingly. 1 In the title. ir
4、ons should read iron. EN comprises 9 pages. Beuth Verlag GmbH, Berlin, has the exclusive right of sale for German Standards (DIN-Normen). DIN EN 10 188 Engl. Price group 8 05.92 Sales No. 1108 EUROPEAN STANDARD NORME EUROPENNE EUROPAISCHE NORM EN 10188 May 1989 UDC 669.1 : 669.14 : 620.1 : 546.76 :
5、543.422 Descriptors: Iron and steel products, steels, cast iron, chemical analysis, chromium, atomic absorption spectrophotometry, flame photometry. English version Chemical analysis of ferrous materials Determination of chromium in steels and irons Flame atomic absorption spectrometric method Analy
6、se chimique des matriaux side- rurgiques; dosage du chrome dans les aciers et les fontes; mthode par spectro- mtrie dabsorption atomique dans la flamme Chemische Analyse von Eisenwerkstoffen; Bestimmung von Chrom in Stahl und Eisen; flammenatomabsorptionscpektrometrisches Verfahren This European Sta
7、ndard was approved by CEN on 1989-05-15. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such
8、 national standards may be obtained on application to the Central Secretariat or to any GEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a GEN member into its own language a
9、nd notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United
10、 Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels O 1989. Copyright reserved to all CEN members. Ref. No. EN 10 188 : 1989 E Page 2 EN 10 188 Brief history This European Standard
11、 takes over the content of EURONORM 188-87, Chemical analysis of ferrous materials - Determination of chromium in steels and irons - Flame atomic absorption spectrometric method, prepared by ECISWTC 20, Methods of chemical analysis, the Secretariat of which is allocated to the Dansk Standardiserings
12、raad (DS). It has been submitted to the CEN Formal Vote following the decision of the Coordinating Commission (COCOR) of the European Committee for Iron and Steel Standardization on It has been adopted and ratified by CEN/BT on 1988-11-05. According to the CEN/CENELEC Internal Regulations, the follo
13、wing countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Note. In clauses 1 and 9, EURONORM shall read European Standar
14、d. 1987-1 1 -24/25. EN 10 188 Page 3 Chemical analysis of ferrous materials Determination of chromium in steels and irons Flame atomic absorption spectrometric method CONTENTS SCOPE AND FIELD OF APPLICATION REFERENCES PRINCIPLE REAGENTS . APPARATUS SAMPLING . PROCEDURE . 7.1 Test portion 7.2 Blank t
15、est . 7.3 Determination 7.4 Establishment of the calibration graph EXPRESSION OF RESULTS TEST REPORT . . ANNEX: Precision data . Page 2 2 2 2 2 3 3 3 3 3 4 5 5 6 Page 4 EN 10 188 1 SCOPE AND FIELD OF APPLICATION This Euronorm specifies a method for the determination of chromium in steels and irons b
16、y means of flame atomic absorption spectrometry. The method is applicable to non-alloy and low-alloy steels and irons with chromium contents ofO.002 to 2.0 %, (m/m) (see Annex). 2 REFERENCES Euronorm I8 - Selection and preparation of samples and test pieces for steel and iron and steel products. Inf
17、ormation Circular No 8 - Recommendations for the drafting of standard methods of analysis employing flame atomic absorption spectrometry for the chemical analysis of iron and steel. Information Circular No 9 - Operational guidelines for the application of flame atomic absorption spectrometry in stan
18、dard methods for the chemical analysis of iron and steel. 3 PRINCIPLE Dissolution of a test portion with hydrochloric acid followed by oxidation with nitric acid. Filtration and ignition of the acid insoluble residue. Removal of silica with hydrofluoric acid. Fusion of the residue with potassium hyd
19、rogen sul- phate. extraction of the melt in acid and addition of the extract to the reserved filtrate. Determination. of the chromium by means of the spec- trometric measurement of the atomic absorption of the 357.87 nm line emitted by a chromium hollow cathode lamp when the solution is nebulized in
20、to a nitrous oxide acetylene flame. 4 REAGENTS During the analysis. use only reagents of recognized analy- tical reagent quality and having a very low chromium content. and only distilled water or water of equivalent purity. 4.1 Iron, of high punty, with a chromium content I m/g- 4.2 Potassium hydro
21、gen sulphate ( KHS04) 4.3 Hydrochloric acid, p I. I9 g/ml approximately. ( 12 mol/l approximately). 4.4 Nitric acid. p 1.40 g/mi approximately, ( 14 mol/ approximately). 4.5 Sulphuric acid. p 1.84 g/ml approximately. ( 18 mol/l approximately). 4.6 Hydrofluoric acid, p 1.15 g/mi approximately. (20 mo
22、l/l approximately). 4.7 Sulphuric acid. p 1.84 g/ml approximately. diluted 1+3 (V/V). (4.5 mol/l approximately). 4.8 Background solution Weigh 10 g of iron (4. I ) into a I litre beaker. Add 1 O g of potassium hydrogen sulphate (4.2) and 150 ml of hydro- chloric acid (4.3). Heat gently until dissolv
23、ed. then oxidize with 30 mi of nitric acid (4.4). added in small portions. Allow to cool. transfer to a 250 ml volumetric flask. dilute to the mark with water and mix. 4.9 Chromium reference solution. corresponding to I mg of chromium per ml. Weigh 1.000 g of high purity chromium metal (3 99.7% (m/m
24、) pure). Transfer to a 250 rnl beaker and dissolve in 40 ml of hydrochloric acid (4.3). Cool, transfer to a I O00 mi volumetric flask, dilute to the mark with water and mix. Note: p equals the density. 5 APPARATUS Ordinary laboratory equipment and 5.1 Atomic absorption spectrometer: a chromium hollo
25、w cathode lamp: supplies of nitrous oxide and acetylene sufficiently pure to give a steady, clear fuel-lean flame, free from water and oil and free from chromium. The atomic absorption spectrometer used will be satisfactory if after optimization according to 7.3.4. the limit of detection and charact
26、eristic concentration are in reasonable agreement with the values given by the manufacturer and it meets the following performance requirements. 5.1.1 Minimum precision The standard deviation of IO measurements of the absorbance of the most concentrated calibration solution shall not exceed 1.5 %, o
27、f the mean absorbance. The standard deviation of IO measurements of the absorbance of the least concentrated calibration solution (excluding the zero calibration solution) shall not exceed 0.S X of the mean absorbance of the most concentrated calibration solution. For example. if the top and bottom
28、calibration solutions represent O. 10 %, and 0.02 %, chromium in the sample. the EN 10 188 Page 5 precision called for (as two standard deviations) would be 0.003 % and 0.00 1 % chromium respectively. assuming curve linearity. 5.1.2 Additional performance requirements It is also desirable that the i
29、nstrument should conform to the following additional performance requirements (see Informa- tion Circular No 8, Section 2): (a) Characteristic concentration - The characteristic con- centration for chromium in a matrix similar to the finai sample test solution shall be better than 0.25 pg/mi. (b) Li
30、mit of detection - The lit of detection of chromium in a matrix similar to the final sample test solution shall be better than 0.05 pg/ml. (c) Curve linearity - The slope of the calibration curve covering the top 20 % concentration range (expressed as a change in absorbance) shall not be less than 0
31、.7 of the value of slope for the bottom 20 % concentration range determined in the same way. For instruments with automatic standardization using only two calibration solutions, one being twice the concentration of the other, the acceptable curve linearirj is limited to such an extent that the absor
32、ption of the lower calibration solution does not exceed 0.55 of the absorption of the higher calibration solution. 5.2 Ancillary equipment A strip chart recorder and/or digital readout device is recommended to evaluate the critena in 5.1 and for all subsequent measurements. 6 SA-MPLING Sampling shal
33、l be carried out in accordance with Eurononn I 8. 7 PROCEDURE 7.1 Test portion Weigh the mass (m), indicated below to the nearest 0.001 g: m- 1 g* I % 7.2 Blank test With each analytical run, carry out an analysis on a reagent blank in parallel with the test portion analysis, using identical reagent
34、s. conditions, analytical procedures and dilutions throughout. 7,. 3 Determination 7.3.1 Preparation of the test solution Place the test portion (7. I ) in a 250 mi beaker. Add I5 ml of hydrochloric acid (4.3). cover the beaker and heat gently until solvent action ceases. Oxidize with 3 ml of nitric
35、 acid (4.4) added dropwise and boil for I minute to remove oxides of nitrogen. Cool, dilute with about 15 ml of water and fdter through a pulp pad prepared from macerated filter paper, collecting the filtrate in a 100 ml volumetric flask. Wash the filter with water. collecting the washings in the sa
36、me 100 ml volumetric flask, but taking care to leave sufficient room for the tusion extrad of the acid insoluble residue. about 20 mi, to be added later. Reserve the filtrate. Transfer the filter and residue to a small platinum capsule or crucible, dry and ignite at as low a temperature as possiole
37、until all carbonaceous matter is removed and finally at about 800 “C for at least 15 minutes. Cool, add 2 drops of sulphuric acid solution (4.7) and about 2 ml of hydrofluoric acid (4.6). Evaporate to dryness, heat to about 800 “C and cool. Add I g of potassium hydrogen sulphate (4.2) and fuse caref
38、iilly until a clear melt is obtained. Nore: For residues which contain chromium carbide. prolonged heating may be necessary for complete fusion. The potassium hydrogen sulphate can be regenerated by allowing the melt to cool, adding 2 drops of sulphunc acid solution (4.5) and repeating the fusion un
39、til the residue has dissolved. Cool and transfer the crucible and solidified melt to a small beaker. Add 10 ml of water and 2 mi of hydrochloric acid (4.3) and heat gently until the solid has dissolved. Cool, add the extract to the reserved filtrate in the 100 ml volumetric flask, dilute to the mark
40、 with water and mix. This is the sample solution S. Set up the instrument as described in 7.3.3. Test the solution S at various approximate dilutions to obtain the dilution factor D, that brings the solution near the midway of the optimum working range of the instrument. e.g. 0.25 to 0.45 absorbance
41、 units. Accurately dilute the sample solution S with water by the dilution factor D to obtain the test solution N. Dilute the blank test solution (7.2) in the same way. Note: Volumes of sample solution S less than 5 mi shall not be taken for dilution. 7.3.2 Preparation of the calibration solution If
42、 the test solution N gives an absorbance above 0.25, accurately dilute the standard chromium solution (4.9) to give a stock solution approximately 600 times the char- acteristic concentration (5. I .2). Using a burette, transfer O. 5, IO, 15, 20 mi of the above chromium stock solution to 100 ml volu
43、metric flasks. Add 25 x /D ml of background solution (4.8) to each and dilute to the mark with water (D is the dilution of the sample solution). If the test solution N gives an absorbance below 0.25, prepare two solutions each containing 25 ml of background solution (4.8) per 100 ml. one containing
44、5 pg/d of chromium, the other no added chromium. Using these, a rough estimate of the chromium in the test solution can be made. Accurately dilute the standard chromium solution (4.9) to give a stock solution of concentration IO times the chromium levei in the test solution. as estimated above. Usin
45、g a burette, transfer O. 5, IO, 15, 20 mi ofthe chromium stock solution to 100 mi volumetric flasks. Add 25 ml of background solution (4.8) to each and dilute to the mark With water. Page 6 EN 10 188 The top standard shall con (b) the need to shield the eyes of the operator from W radiation by means
46、 of tinted glass; (c) the need to keep the burner head clear of deposits. A badly clogged burner may cause a flash back: (d) the need to ensure that the liquid trap is filled with water. See also Information Circular No 9 - Appendix C. 7.3.4 Optimization of the atomic absorption spectrometer setting
47、s FoUow the manufacturers instructions for prepdng the instrument for use. (See also Information Circular No 9 - Appendix A). When the current to the lamp, the wavelength and the flow of gas have been adjusted and the burner lit, spray water until the indication has stabilized. Set the absorbance va
48、lue to zero. Choose a damping setting or integration time to give a signal steady enough to fulfil the precision requirements (5. I. I). Adjust the flame to be fuel-lean and the burner height to about I cm below the light path. Spraying, alternately, the high and zero calibration solutions. adjust t
49、he gas flow and burner position (horizontally. vertically and rotationally) until the difference in absorbance between the calibration solutions is at a maximum. Check that the spectrometer is set on the required wavelength. Evaluate the criteria of 5. I. I to ensure that the instrument is suitable for the determination. 7.3.5 Atomic absorption measurements Set the scale expansion so that the top calibration solution gives nearly full scale deflection. Aspirate the calibration solutions in ascending order repetitively until each gives the specified precision (5. I. 1 ) t
