wtw photolab S12 Operating Instructions Manual page 15

3 Sample Preparation
The manner in which the sample is pretreated en ables the three pro-
portions to be dis tinguished from each other. This can be illustrated using
a copper-containing waste water sample as an example.
Example
Decomposition
Total content
Solid Substances
Cu(OH)
2
Complexes Cu-EDTA Complexes Cu-EDTA
2+
Ions Cu
Result A
Proportion:
Ionogenic
Complex
Solid Substances
Total content
Decomposition converts the substance to be deter mined into an ana-
lyzable form. In most cases, de composition agents take the form of acids
in com bination with oxidiz ing agents; in exceptional cases (e. g. in the
determination of total nitrogen) an alka line decomposition is more effec-
tive. The type of decomposition procedure used de pends on the analyte to
be determined and the sample matrix.
The ready-to-use sample-decomposition products Spectro quant
Set 10 and 20 are suited for the preparation of the sample materials for
the determinations stated in the table.
The decomposition processes are carried out in the Spectro quant
moreactor (capacity: 12 or 24 decomposition cells) at 120 °C or, respec-
tively, 100 °C. Details regarding the heating times and further treatment
can be found in the package inserts contained in the Spectroquant
Crack Set packs.
Determination of
Total phosphorus*
Total chromium*
[ = sum of chromate and chromium(III)]
Total metal
[ = sum of free and complex-bound metal]
Total nitrogen*
* The decomposition reagents are already contained in the packs of the respective cell tests.
** Decomposition cells are included in the pack; empty cells are required for the decomposition for
Crack Sets 10 and 20.
Release 01/2012
Filtration
Decomposition Filtration
Dissolved proportion Dissolved proportion
2+
Ions Cu Ions Cu
Result B Result C
= C
= B – C
= A – B
= A
Sample preparation with
Crack Set 10 / 10 C**
Crack Set 10 / 10 C
Crack Set 10 / 10 C
Crack Set 20
2+
®
Crack
®
ther-
®
photoLab ® Series
13