EN 29658:1991

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.FLMVNRStahl - Bestimmung des Aluminiumgehalts - Spektralfotometrische Atomabsorptionsmethode (ISO 9658:1990)Aciers - Dosage de l'aluminium - Méthode par spectrométrie d'absorption atomique dans la flamme (ISO 9658:1990)Steel - Determination of aluminium content - Flame atomic absorption spectrometric method (ISO 9658:1990)77.080.20JeklaSteels77.040.30Kemijska analiza kovinChemical analysis of metalsICS:Ta slovenski standard je istoveten z:EN 29658:1991SIST EN 29658:1997en01-december-1997SIST EN 29658:1997SLOVENSKI
STANDARD
IS0 9658:1990(E) 8.3.1.3 Preparation of the test solution for the determination of acid-soluble aluminium If acid-soluble aluminium only is required, add 5,0 ml of fusion mixture solution (5.8) to the 100 ml one-mark volumetric flask, cool, and allow any car- bon dioxide produced to escape, then dilute to the mark with water and mix. Discard the insoluble res- idue and cellulose nitrate filter. Retain this solution for the determination of acid-soluble aluminium. 8.3.1.4 Preparation of the test solution for the determlnatlon of total aluminium Transfer the filter containing the insoluble residue into a platinum crucible (6.4). Char the residue at low temperature and ignite slowly to 1000 “C. Cool the crucible. Add several drops of water, several drops of sulfuric acid (5.5) and 5 ml of hydrofluoric acid (5.2). Evaporate to dryness and again ignite slowly to 1000 “C. Cool the crucible and add I,0 g of the fusion mixture (5.7). Fuse the contents of the crucible in a muffle furnace at 1000 “C for 15 min. Cool the crucible and add 1 ml or 2 ml of hydrochloric acid (5.3) and 8 ml of water to the solidified melt. Heat gently to dissolve the fusion products. Allow the crucible to cool and transfer the solution quantitatively to the filtrate in the 100 ml one-mark volumetric flask. Dilute to the mark with water and mix. Retain this solution for the determination of total aluminium. 8.3.2 Preparation of the calibration solutions 8.3.2.1 Aluminium contents c 0,010 % (m/m) Introduce into a series of five 250 ml beakers (2,00 + 0,Ol) g of the pure iron (5.1). Add 40 ml of acid mixture (5.6) in small portions, to each beaker and cover them with watch-glasses. Heat until the iron is in solution, then boil to eliminate oxides of nitrogen. Cool and transfer the solutions into five 100 ml one-mark volumetric flasks. Using a burette add the volumes of aluminium standard sol- ution B (5.9.3) as indicated in table 1. Add 5,0 ml of fusion mixture solution (5.8) to each flask. Cool and allow any carbon dioxide produced to escape, then dilute to the mark with water and mix. I Table I Volume of alu- Corresponding minium stand- concentration of ard solution B aluminium in (5.9.3) final test sol- ution ml jLg/ml 0 1) 0 295 03 50 190 795 13 IO,0 290 1) Zero member. Corresponding content of alu- minium in test sample O/o (m/m) 0,000 0 0,0025 0,005o 0,0075 0,0100 8.3.2.2 Aluminium content between 0,010 % (m/m) and 0,20 % (m/m) Proceed as specified in 8.3.2.1, using table 2 instead of table 1. Table 2 Volume of alu- Corresponding minium stand- concentration of Corresponding aluminium in content of alu- ard solution A minium in test (5.9.2) final test sol- ution sample ml jlg/mi O/O (m/m) 0 1) 0 0,000 590 IO,0 0,050 IO,0 20,o 0,100 15,o 30,o 0,150 20,o 40,o 0,200 1) Zero member. 8.3.3 Adjustment of atomic absorption spectrometer See table 3. 8.3.4 Optlmlzlng the atomic absorption spectrometer settings Follow the manufacture the instrument for use. r’s instructions for preparing 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. 4 SIST EN 29658:1997

IS0 9658:1990(E) Element Type of lamp Wavelength Flame Lamp current Bandwidth Background correction Table 3 Characteristic Aluminium hollow cathode. 309,3 nm Dinitrogen monoxide-acetylene non-luminous oxidizing flame. The height of the red-feather flame shall be 10 mm to 20 mm adjusted for maximum aluminium response. Follow manufacturer’s recommendations. Follow manufacturer’s recommendations. If no recommendation is stated, a bandwidth between 0,2 nm and 0,7 nm is suggested. If the zero member gives an absorbance comparable with the precision of the lowest calibration solution, background correction may be required. WARNING - The manufacturer’s recommendations should be closely followed and particular attention is drawn to the following safety points: a) the explosive nature of acetylene, and regulations concerning its use; b) the need to shield the eyes of the operator from ultraviolet radiation by means of tinted glass; c) the need to keep the burner head clear of deposits because a badly clogged burner may cause a flashback; d) the need to ensure that the liquid trap is filled with water; e) always spray distilled water between the test solutions, blank solution and/or calibration solutions. Set the absorbance value to zero using water. Choose a damping setting or integration time to give a signal steady enough to fulfil the precision criteria of 6.5.1 to 6.5.3. Adjust the flame to be non-luminous and oxidizing with an approximate 10 mm to 20 mm of red feather. Spraying alternately the calibration solution of high- est concentration and the zero member (see table I), adjust the gas flow and burner position (horizontally, vertically and rotationally) until the difference in absorbance between the calibration solution is at a maximum. Check that the spectrometer is set accurately on the required wavelength. Evaluate the criteria of 6.5.1 to 6.5.3 and the addi- tional performance requirement of 6.5.4, to ensure that the instrument is suitable for the determination. 8.3.5 Spectrometric measurements Set the scale expansion so that the calibration sol- ution of highest concentration gives nearly full scale deflection. Spray the calibration solutions in as- cending order repetitively until each gives the spec- ified precision, thus showing that the instrument has achieved stability. Select two calibration solutions, one having an absorbance just lower than the test portion solution and one just higher. Spray these first in ascending order, then in descending order, with the test solution as the middle solution, in each case measuring the absorption in relation to water. Spray the complete range of calibration solutions, including the zero member. Then spray again in as- cending and descending order. The means of the last ascending and descending series of calibration solutions are used for the calibration graph. It is recognized that these procedures cannot be followed with automatic instruments which accept two calibration solutions only. In this case it is sug- gested that the two “sandwiching” solutions should not be used for the primary calibration but should be analysed alternately with the test solution. Spray calibration solutions at frequent intervals during the measurement of a batch of determi- nations. Clean the burner if the results show loss of precision caused by clogging. Obtain the mean absorbance of the test solution and the mean absorbance of the blank solution. 8.4 Plotting the calibration graph It is necessary to prepare a new calibration graph for each series of determinations, and for the range of aluminium contents expected. If pure metals and reagents have been used, the blank test and zero member should give very small absorbance readings with a negligibly small differ- 5 SIST EN 29658:1997

IS0 9658:1990(E) ence. In this case, prepare a calibration graph by plotting the mean absorbance values of the cali- bration solutions against micrograms of aluminium per millilitre. Refer the mean test solution absorbance and the absorbances of the two adja- cent calibration solutions to the graph. If, however, the zero member has a significant absorbance, a more complicated procedure is re- quired. In this case, the concentration of aluminium pz in the zero member can be calculated using the formula A Z PZ =&lx A A cl- z where PC1 is the concentration of aluminium, ex- pressed in micrograms per millilitre, added to the first calibration solution; A Z is the absorbance of the zero member; A cl is the absorbance of the first calibration solution. The derived value pz is then added to each of the nominal calibr
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