COMMITTEEDRAFT
ISO/CD 15151 | IDF 229
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–
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5
9.1.1 Test portion for dryashing
9.1.1.1 Milkandwhey
Weigh, to the nearest 1mg, 10 gof prepared test sample (8.1) in the crucible (6.8).
9.1.1.2 Driedmilk, driedwhey, infant formula and cheese
Weigh, to the nearest 1mg, 1 g of prepared test sample (8.2, 8.3) in the crucible (6.8).
NOTE
The added quantitiesmay bemodified. Aim is to arrive at a content of drymatter in the crucible equivalent to
the drymatter of 10 gmilk orwhey.
NOTE If repeatability in samples does not meet with the criteria, a pre step to reduce variation of homogeneity has to
bemade. Dissolve25 grampowder in 250gramwater and then take an aliquot for analysis
.
9.1.2 Test portion forwet digestion
WARNING— When using a system running under pressure (pressurized microwave assisted wet
decomposition system), special attention shall be paid to avoid any risk of explosion. Inparticular the
size of test portion has to be especiallywell considered. In a decomposition vessel of about 75ml, no
moreof anysample shall bedigested corresponding to anamount of drymatter of 1g.
9.1.2.1 Milkandwhey
Weigh to thenearest 1mg, 4g of prepared test sample (8.1) in themicrowave vessel (6.10)
or digestion tube
.
9.1.2.2 Driedmilk, driedwhey, infant formula and cheese
Weigh to the nearest 1mg, 1 g of prepared test sample (8.2) or 0.5-0.8g cheese (8.3) in themicrowave vessel (6.10) for
pressuriseddigestion
.
Weigh to the nearest 1mg , 0,4 g
–
0,5gof prepared test sample (8.2) or 0.3g cheese (8.3) intoa digestion tube.
9.1.2.3 Blank test
In parallel with the procedure of the test portion, carry out a blank test using the same procedure and the
same amount of each reagent being added in the decomposition (9.2) and the determination (9.3) steps of the
test portion.
NOTE
The addedquantitiesmay bemodified.
9.2 Decompositionof organicmatter
9.2.1 Dryashing
Place the crucible (9.1.1.1 or 9.1.1.2) and 2 empty crucibles (for blank test) into the programmable furnace
oven (6.9) at room temperature.
Start the heating program which includes the following steps: for drying and pre-ashing steps increase the
temperature by 50 °C per h up to
550
°C. Keep for ashing of the test portion the temperature of the oven at
550
°C overnight for 6 to 18 h. If the obtained ash of the test portion still has a grey colour after cooling down,
dissolve the ash in 1 ml nitric acid solution (5.2). Continue the dry ashing by repeating the procedure from
beginning 9.2.1.
9.2.2
Wet digestion
MTE-03
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