ISO-10775-1995.pdf
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1、INTERNATIONAL STANDARD ISO 10775 First edition 1995-05-15 Paper, board and pulps - Determination of Cadmium content - Atomic absorption spectrometric method Papier, carton et pates - Determination de Ia teneur en Cadmium - Methode par spectrom also run a blank (see clause 8). 7.1 Test Sample prepara
2、tion Weigh a test Portion of 1 g to the nearest 1,O mg and transfer it to the appropriate PTFE vessel (5.1). Add 10 ml of the concentrated nitric acid (4.1). Close the vessel with its lid and place it in the autoclave (5.1 .l) or in the microwave oven ( 5.1.2), as applicable. 7.2 Combustion procedur
3、e 7.2.1 Autoclave procedure If an autoclave is used, close the autoclave as in- structed by the manufacturer and place it in the heat- ing block (5.1 .l). Heat it at (160 + 5) “C for (16 + 1) h. Allow the heating block and the autoclave - to cool and, with caution, open the autoclave in a hood. Proc
4、eed to 7.3. 7.2.2 Microwave oven procedure If a microwave oven is used, the test Portion size shal be adjusted to the capacity of the digestion vessel If this is 120 ml, the maximum test Portion mass shal be 0,3 g. If more test Portion is taken, the safety valve of the digestion vessel will activate
5、. Set the power regulator to the predetermined value and heat the closed digestion vessel (5.1.2), with its contents for 60 min. Allow the vessel to cool and, with caution, open it in a hood. The correct setting of the power regulator shall be determined separately for each oven. A typical setting i
6、s 40 % of maximum power. See also 5.1.2. 7.3 Diktion Allow nitrous fumes to escape from the wet com- bustion vessel and dilute the remaining Solution to a known volume with water. The dilution volume de- pends on the equipment used, and should be kept as small as possible. The dilution tan be made i
7、n a disposable graduated plastic vessel. The use of volumetric flasks is not recommended because of the risk of contamination. Alternatively, dilute the remaining Solution directly in the digestion vessel by adding from a graduated pipette the required volume of water. In this case, the volume of th
8、e residual nitric acid shall be determined in a separate experiment. Allow any suspended solids to settle. 8 Blank Follow the instructions in clause 7, but use no Sample. 9 Preparation of calibration solutions Prepare the calibration Solution daily by diluting the stock calibration Solution (4.4) wi
9、th dilute nitric acid (4.2). The Cadmium content selected for the final calibration Solution depends on the particular instru- ment to be used. In general, a calibration Solution having a Cadmium mass concentration of 10 pg/l (0,Ol pg/mI) is appropriate. 10 Determination of Cadmium 10.1 The procedur
10、e for the spectrometric determi- nation of the Cadmium content of the test solutions depends on the design of the atomic absorption spectrometer (5.2) and of the graphite furnace. The manufacturer s instructions should be followed when operating the instrument. In general, the technique with Standar
11、d additions (see 10.2) should be used. In practice, the normal cali- bration procedure, based on a calibration curve, may be used, provided that there is no interference from the matrix. This must be verified by analysing suitable reference materials. Before using the normal calibration procedure, c
12、heck that any matrix effects are under control by running the Same type of Sample by the Standard addition technique. In particular, differentes in acid concen- tration between Standards and Sample solutions af- fett the results. The acid concentration of the Standard solutions should be adjusted to
13、 that of the Sample solutions by replacing part of the diluent (4.2) by concentrated nitric acid (4.1). 10.2 For the technique with Standard additions, the following instructions are given as a guide. Prepare the solutions for measurement directly in the graphite tube by means of a Sampler. Typical
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