COMMITTEEDRAFT
ISO/CD 15151 | IDF 229
6
© ISO2010
–
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Either use pressurized microwave assisted wet digestion system (6.10) or any appropriate instrumentation in
wet digestion.
9.2.2.1 Pressurizedmicrowave assistedwet digestion systemwithout internal standard
Place the vessels containing the test sample (9.1.2.1 or 9.1.2.2) in a fume cupboard. Add 10ml of nitric acid
(5.2). Swirl gentlyandwait a fewminutes before closing the vessel.
Place the vessel into the microwave oven (6.10). Apply the decomposition program with the pressurized
systemmentioned in table 1.
NOTE The parameters such as type and volume of reagent to be added, themicrowave power and decomposition time
canbemodified according to the type and size of test sample to analyze.
Table1—Pressurizedmicrowave assisteddigestion system - Decompositionprogramme
Step
Outset Pressure
(W)
Time
(min)
Final Temperature
(°C)
Cooling
System
1
Max. 1600
20
180-200
Low
2
Max.1600
35
180-200
Low
3
0
15
<50
High
9.2.2.2 Pressurizedmicrowaveassistedwet digestion systemwith internal standard
Place the vessels containing the test sample (9.1.2.1 or 9.1.2.2) and blank (9.1.2.3) in a fume cupboard. Add
10ml of nitric acid (5.2) and 0,125 ml of internal standard solution (5.6). Swirl gently and wait a fewminutes
before closing the vessel. Place the vessel into themicrowave oven (6.10). Apply the decomposition program
with the pressurized systemmentioned in table 1.
NOTE The parameters such as type and volume of reagent to be added, themicrowave power and decomposition time
canbemodified according to the type and size of test sample to analyze.
9.2.2.3 Unpressurisedwet digestionwithout internal standard.
Add 7ml of digestion solution (30%H
2
O
2
: HNO
3
50:50 [volume fraction]) to each tube. Heat samples at 85 °C
± 2 °C for 45min. Dilute to 50ml andmix
9.3 Determination
9.3.1 Preparationof the test solution
9.3.1.1 Dryashing
Add 1ml of nitric acid (5.2) toall crucibles and dissolve the obtainedash (9.2.1).
Transfer quantitatively the crucible content into a 50ml one-mark volumetric flask (6.3) by rinsing with water.
Add 0,25ml of internal standard solution (5.6) in case of dry ashing with internal standard. Dilute to the 50ml
markwithwater. Mix thoroughly. If necessary, continuewith the dilution procedure in9.3.1.4.
9.3.1.2 Wet digestionwithout internal standard
Cool the digested solution (9.2.2.1) to room temperaturewhile reducing toatmospheric pressure.
MTE-03
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