Page 18 - 1_Environmental analysis

SCA-130-108

The module is fully integrated into the TOC- Calibration of the IC is carried out in the same
Control software which automatically way, for instance using sodium hydrogen
calculates the TOC-content. carbonate.

■ NPOC determination ■ Detection limit
For the NPOC method, the sample is The detection limit for this method is at
acidified in order for the CO 2 to be purged 0.1 mg C. For a soil sample weight of 1 g, a
from the carbonates and hydrogen theoretical detection limit of 0.01 wt.% TOC is
carbonates. This pretreated sample is then obtained.
used to determine the TC (and thus the
NPOC). ■ Example of a solid sample measurement
Sample type: contaminated soil
■ Additives
Large amounts of earth-alkali compounds Sample weight: 1 Peak: 110 mg
st
such as barium or calcium carbonate can be 2 Peak: 190 mg
nd
difficult to determinate. Bicarbonate, for
instance, needs temperatures up to 1200°C Result: 1.) 4.04 % TC
to be thermally decomposed. 2.) 4.08 % TC

Small amounts of additives such as vanadium Mean value: 4.06% TC
(V) oxide or tungsten oxide are added to such
samples. They act as catalysts and ensure 1000
complete determination.

■ Calibration 600
Calibration can be performed in different Signal[mV]
ways. Usually, the calibration is carried out in 300
the solid sample module using different
sample weights of a solid with known carbon 0
content, for instance glucose which contains -100
40% carbon. For the different sample weights 0 5 10
(in µg absolute carbon), the absolute amount Zeit[min]
of carbon is plotted on the X-axis of the Abb.: Peaks for various sample weights.
calibration graph.
Kal. Kurve
2136,2
■ Recommended instrument / equipment
TOC-L CXX
1500
TOC-V WX
Fläche 1000 SSM-5000A

500

0
0 4000 8000 12000 18101,6
Abs C [ug]

Abb.: TOC calibration in the SSM-5000A using
Glucose.