EN 1122-2001 pdf download.Plastics-Determination of cadmium -Wet decomposition method.
5 Apparatus
5.1 Apparatus for wet decomposition (e.g. Figure 1), Kjeldahl flask or any other suitable apparatus for wet decomposition.
5.2 Hot plate
5.3 Fume cupboard, preferably with air washing.
5.4 Flame atomic absorption spectrophotometer with background correction, e.g. 02 or Zeemann
(ISO 3856-4:1984).
5.5 Hollow cathode lamp or EDL for cadmium (ISO 38564:1984).
5.6 Analytical balance with range of 1 mg.
5.7 Membrane filter with a pore size of 0,45 ,im.
6 Test procedure
6.1 Test sample
Use homogeneous samples of at least 2 g for the analysis. Cut the sample into smaller pieces with a knife or scissors preferably in pieces less than 0,1 g.
6.2 Test portion
Weigh approximately 0,5 g of the test samples (6.1) to the nearest mg into a decomposition apparatus, e.g. a Kjeldahl flask (5.1). Carry out the analysis in duplicate.
6.3 Wet decomposition
The necessary time and reagent consumption for the decomposition depends on the particle size of the sample and mainly on the plastic materials.
6.3.1 Method A
Wet decomposition by a mixture of sulfuric acid, nitric acid and hydrogen peroxide. The following method describes the decomposition in the decomposition apparatus (Figure 1), but any other suitable apparatus can be used (5.1). Carry out the decomposition in a fume cupboard (5.3).
To flask B of the decomposition apparatus (Figure 1), add 10 ml of sulfuric acid (4.1). Connect the flask to the condensate reservoir, run water into the condenser, close taps R I and R 2 and add 10 ml of nitric acid (4.2) into the funnel. Using tap R 1, allow 1 ml to 2 ml of the nitric acid to run, then moderately heat until the material changes into a black mass and white fumes of SO3 are liberated. Now stop heating and allow I ml to 2 ml of the nitric acid to fall in drops. Reheat until white fumes appear. Repeat this procedure until a light yellow coloured solution is obtained.
After the addition of Itie last portion of nitric acid, open tap R 2 and allow the condensate to run into the flask, first dropwise in order to prevent a too violent reaction, then more rapidly. Close tap R 2. reheat until white fumes are produced. Allow to cool for some minutes and add about 5 ml of hydrogen peroxide (4.3) into the flask using the funnel. Complete the decomposition by reheating for about 5 minutes.
Stop heating, open tap R 2 and allow the condensate to drop slowly into the flask. After cooling to room temperature, rinse the apparatus with water and decant quantitatively into a 100 ml one-mark volumetric flask. Dilute to the mark by adding distilled water and mix well.
If insoluble matter exists at this stage which might disturb the atomic absorption method, then remove it by filtration, using a dry membrane filter (5.7).
Prepare a reagent blank solution In the same way without using a test sample.
6.3.2 Method B
Wet decomposition by a mixture of sulfuric acid and hydrogen peroxide. The following method describes the decomposition In a Kjeldahl flask but any other suitable apparatus can be used (5.1). Carry out the decomposition in a fume cupboard (5.3).
Place the flask and its contents on the hot plate (5.2), add 10 ml of the sulfuric acid (4.1) and heat at a higher temperature to decompose and carbonize the organic substances. When white fumes are evolved continue heating for about 15 minutes.
Take the flask from the hot plate and allow to cool for about 10 minutes. Add slowly, from the funnel, four 5 ml portions of hydrogen peroxide solution (4.3), allowing the reaction to subside after each addition.
Note Because of the danger of splattering, any reaction flask should be kept covered between additions of hydrogen peroxide solution,
Heat again for about 10 minutes arid allow to cool for about 5 minutes. Add further 5 ml portions of the hydrogen peroxide solution and heat again. Stop this procedure only when no more organic matter remains. Allow to cool to room temperature and dilute cautiously with water. Rinse the flask with water and decant quantitatively into a 100 ml one-mark volumetric flask. Dilute to the mark by adding distilled water and mix well. If insoluble matter exists at this stage which might disturb the atomic absorption method, then remove it by filtration, using a dry membrane filter (5.7).
Prepare a reagent blank solution in the same way without using a test sample.
6.4 Determination
Determine the cadmium concentration of the test solutions and the reagent blank solution obtained according 106.3, by the method described in clause 3 of ISO 3856-4:1984.
Note The sulfuric acid in the test and reagent blank solution might influence the results of the flame atomic absorption method; therefore use a background correction (5.4).
For the determination of the cadmium concentration of the test solutions and the blank solutions other suitable techniques can be used, e.g. inductively-coupled plasma (ICP) or an isotope specific method. The used technique shall be noted in the test report.
7 Expression of results
The total cadmium content of the sample is given by the following formula in mglkg:EN 1122-2001 pdf download.