Page 32 - Application Handbook - TOC

Sum parameter – Total Organic Carbon
TOC – Determination in sulfuric acid
SCA-130-303
Acids are a group of frequently used
inorganic chemicals used in the chemical
industry. In particular, sulfuric acid is used in
a wide range of applications.
Sulfuric acid in a concentration range to
1%.can be directly measured using a TOC-L
analyzer Higher sulfuric acid concentrations
can lead to tailing and, consequently to
increased measurement values because high
sulfate concentrations (> 5000 mg/L) can
lead to the formation of large amounts of SO 2
vapors. SO 2 exhibits absorption bands in the
same IR detection range as CO 2 and can,
therefore, be misinterpreted for CO 2.
To determine organic contaminations in
highly concentrated sulfuric acid, additional
SO 2 scrubbers are used.
The following SO 2 scrubbers are available:
 Sulfix (WAKO Chemicals, Fuggerstr. 12,
41468 Neuss, Germany). The Sulfix
scrubber is installed underneath the
normal sensitive catalyst and enables
selective filtration of the formed SO 2.
 Mist scrubber (cartridge)
Just like the halogen scrubber, the ‘Mist
scrubber’ is used in the flow line for SO 2
absorption.
In the experiment described below, the
NPOC content of a 98% sulfuric acid solution
is determined.
The required purity criterion and the required
limit of detection was < 10 mg/L.
■ Sample preparation
The concentrated sulfuric acid was diluted
with ultrapure water to a ratio of 1:10 to
decrease the concentration as well as the
viscosity of the sulfuric acid.
Compound
(Concen- Dilution Conc.
tration)
1 : 10 diluted
Sulfuric with water Ca. 10%
acid (98%)
(5m/50ml)
The dilution has to be carried out with the
utmost care and caution, as the sulfuric acid
reacts violently upon the addition of water
(heat generation).