Page 28 - Application Handbook - TOC
P. 28
Sum parameter – Total Organic Carbon
TOC – Determination in hydrochloric acid
SCA-130-301
Acids, in particular concentrated hydrochloric In general, it is possible to greatly dilute the
acid, represent a large group of inorganic substance to be analyzed in order to
chemicals frequently used in the chemical eliminate matrix interferences. But sometimes
industry. TOC determination in concentrated it is necessary to achieve very low limits of
hydrochloric acid poses an enormous detection (with reference to 37% hydrochloric
challenge to the analyzers that are used for acid) of 1 mg/L.
this purpose.
■ TOC Measuring Method
The 37% hydrochloric acid solution was
manually diluted to a ratio of 1:2 with water in
order to obtain an 18.5% hydrochloric acid
solution.
TOC-L CPH with OCT-L
■ Acid challenge
The great challenge is to develop protective
mechanisms to help protect instruments and
their components, as well as to prevent Abb.2 Mehrpunktkalibration mit
damage by acidic fumes. For this purpose, Verdünnungsfunktion
the TOC-L series offers several gas washers Calibration was carried out in the range of 0.5
that bind and eliminate the chlorine gas to 10 ppm. The automatic dilution function of
formed in the flow line of the system in the analyzer automatically executes this
various ways. calibration from a single stock solution. The
injection volume was 150 µL. In case the
TOC contamination of the hydrochloric acid
Another challenge is to attain a stable and exceeds the measuring range of the
reproducible oxidation process to ensure that calibration, the automatic dilution function of
no fluctuating or tailing peaks are being the analyzer will readjust the hydrochloric
recorded. In addition, the measuring values acid solution to fit the measuring range.
should remain stable over a longer measuring
interval. ■ Verification the measuring method
After calibration, the TOC content of the
concentrated hydrochloric acid solution was
determined.
