Page 38 - Application Handbook - TOC

Sum parameter – Total Organic Carbon

TOC – Determination in soda solution

SCA-130-306

Impurities in products can be caused by In the case described here, a 50% soda
organic contaminants present in basic solution was investigated. The required
chemicals to. That is a reason why quality detection limit was 10 mg/L.
control of the reactants is indispensable.
■ Sample preparation
The sample was first manually diluted to a
ratio of 1:10 with ultrapure water and a
corresponding amount of acid. Several mL of
ultrapure water were placed in a 50 mL
volumetric flask. Subsequently, 5 mL of the
concentrated soda solution was pipetted into
the flask. Finally, concentrated sulfuric acid
was added until the solution has reached a
pH < 2.
The flask was then filled with ultrapure water
up to the mark.
Compound Dilution Conc.
(Concen-
tration)

Soda 1 : 10 diluted Approx.
hydroxide with water 5%
solution (5ml/50ml)

(50%) add. 1-2 drops
Sulfuric acid
until pH<7

In the determination of organic
contaminations in concentrated soda
solutions, various issues must be considered. Caution: During the addition of the sulfuric
In comparison to organic carbon, the soda acid, the carbonates decompose under a
solution to be investigated has a very high violent reaction (heat dissipation / gas
inorganic carbon content in the form of formation).
carbonates. In addition, the solution has a
high pH value and tends to absorb carbon
dioxide from the air.

A soda solution must, therefore, be analyzed
using the NPOC method.