Metrohm 909 UV Digester - Manual (Page 10)

1.2 Function description
￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
2 ￭￭￭￭￭￭￭￭
909 UV Digester
of the fire prevention measures prescribed for laboratories is also manda-
tory.
1.2 Function description
Through the effects of UV radiation, dissolved organic matter that disrupts
the trace analysis of heavy metals is decomposed. However, the UV radia-
tion itself does not cause the digestion of the organic sample compo-
nents; rather, hydroxyl radicals that form break down the organic matter.
Hydroxyl radicals are initially formed from the added hydrogen peroxide
that functions as the initiator for the radical chain reaction. Subsequently,
additional hydroxyl radicals are generated from the water if the tempera-
ture is high enough. Depending on the sample matrix, it may be necessary
to add more H
2
O
2
during digestion.
Spectrum of the UV lamp
The following figure shows a typical spectrum for the UV lamp. Certain
deviations from this spectrum are possible; this can be traced back to pro-
duction-related factors.
100
90
80
70
60
50
40
30
20
10
0
200 300 400 500 600 700
Intensity [%]
Wavelength [nm]
1 2
Figure 1 UV lamp spectrum