Page 18 - 3_Chemical industry

SCA-130-308

■ Results
■Kit for high-salt samples The duplicate determination of the salt
The TOC-L series features a kit for high-salt solutions yielded the following results:
samples, which significantly increases the
instrument’s availability. The kit consists of a Sample NPOC RSD
combustion tube of a special geometry and a [mg/kg] [%]
unique catalyst mixture. Sodium nitrate (>99,9%) 22,8 4,7
Sodium nitrate (>99,9%) 24,0 6,8
Sodium nitrate (>99,9%) <10 ‐
(9,0)
Sodium nitrate (>99,9%) 10,2 5,4

10
9
Signal[mV] 6 3

0
-1
0 5 10 15 20
Zeit[min]
Fig. Example peaks: Sodium nitrate

In this application, sample acidification is
carried out with sulfuric acid which is used to
modify the sample matrix. Due to the higher
melting point of NaSO 4 (888 °C) compared to
801 °C of NaCl the lifetime of the combustion
tube is longer.

■ Interferences
The combustion of nitrogen compounds can
lead to the formation of nitrous oxide gas. ■ Recommended Analyzer / Configuration
Nitrous oxide exhibits absorption bands in the TOC-L CPH
same IR detection range as CO 2 and can, ASI-L
therefore, be misinterpreted for CO 2. In High-Salt-Kit
addition, nitrous oxide can cause tailing and B-Type-Scrubber
can affect the peak symmetry.

A B-type scrubber is used to eliminate
possible interference by nitrous oxide. Due to
the high solubility of N 2O in water, the gas is
dissolved in the B-type scrubber and will not
reach the detector.