ISO 9647:2020 pdf download – Steel – Determination of vanadium content一Flame atomic absorption spectrometric method (FAAS).
5.8 Vanadium standard solution, 0,08 gIl.
Transfer 10,0 ml of vanadium standard solution (1) into a 250 ml one-mark volumetric flask. Dilute to the mark with water and mix.
Prepare this solution immediately prior to use.
1 ml of this solution contains 0.08mg of vanadium.
6 Apparatus
All volumetric glassware shall be class A, in accordance with ISO 648 or ISO 1042, as appropriate.
Ordinary laboratory apparatus and the following shall be used.
6.1 Atomic absorption spectrometer
The spectrometer shall be equipped with a vanadium hollow-cathode lamp and supplied with dinitrogen monoxide and acetylene sufficiently pure to give a steady clear fuel-lean flame, free from water and oil, and free from vanadium.
The atomic absorption spectrometer used will be satisfactory if. after optimization according to 813. the limit of detection and characteristic concentration are in reasonable agreement with the values given by the manufacturer and It meets the performance criteria given in 6J.d to (La.
The instrument should also conform to the additional performance requirement given in 6J.A.
6.1.1 Minimum precision (see Annex C)
The standard deviation of ID measurements of the absorbance of the most concentrated calibration solution shall not exceed 1.0% of the mean absorhance of this solution.
The standard deviation of 10 measurements of the absorbance of the least concentrated calibration solution (excluding the zero memherj shall not exceed 0,5 % of the mean absorbance of the most concentrated calibration solution.
6.1.2 LImit of detection (see Annex C)
The limit of detection is a number, expressed in units of concentration (or amount) that describes the lowest concentration level (or amount) of an element that can be determined to be statistically different from an analytical blank.
The limit of detection of vanadium in a matrix similar to the final test solution shall be less than 0,3 igJml.
6.1.3 Calibration linearity (see Annex C)
The slope of the calibration line covering the top 20 % of the concentration range (expressed as a change in absorbance) shall not be less than 0.7 times the value of the slope for the bottom 20 % of the concentration range determined in the same way.
For instruments with automatic calibration using two or more standard solutions, it shall be established prior to the analysis, by obtaining absorbance readings, that the above requirements for calibration linearity are fulfilled.
6.1.4 CharacterIstic concentration (see Annex C)
The characteristic concentration for vanadium in a matrix similar to the final test solution shall be greater than I ug/ml.
WARNING — The manufacturer’s recomniendations 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) the need always to spray water between the test solutions, blank solution and/or calibration solutions.
Evaluate the criteria of 6.1.1 to 6.1.3 and the additional performance requirement of 6.1.4 to ensure that the instrument is suitable for the determination.
8.3.4 Spectrometrlc measurements Spectrometric measurement of the calibration solutions
Nebulize the relevant series of calibration solutions (83.2.1 or depending on the expected vanadium content in succession into the [lame and measure the absorhance for each solution. Take care to keep the aspiration rate constant throughout the preparation of the calibration curve. Nebulize water through the burner after each measurement, see note.
NOTE For certain types of apparatus it is preferable to use a solution containing the attack reagents in the same concentrations as in the test portion solutions, instead of water. Calibration curves
Subtract the mean absorbance value obtained for the zero-member calibration solution from the mean absorbance values obtained for the other calibration solutions.
Establish the appropriate calibration curve by plotting the net absorbance values of the calibration solutions against the concentration of vanadium, expressed in micrograms per millilitre. Use appropriate spectrometer software or an off-line computer for regression calculations or prepare a graphical representation.
If pure metals and reagents have been used, the zero member should have a negligibly small absorbance.
IF, however, the zero member has a significant absorbance a more complicated procedure is required. In this case, the concentration of vanadium c, expressed in micrograms per millilitre (pg/mI), in the zero member can be calculated using Formula (1).