16 User Manual QuickTOC
®
purity
ATEX 2 04E3920
2 Operating Principle of the Analyser
2.1 Measurement of TOC LAR | PROCESS ANALYSERS AG
The water vapour produced by oxidation is condensated out by a cooler, and remaining corrosive com-
bustion gasses are then cleaned by the filters. Then the CO
2
concentration is determined in a NDIR de-
tector and output as the TOC.
2.1.5.2 Advantages
The direct method is recommended for determining the TOC when the concentration of the anorganic
carbon is considerably greater than the concentration of the organic carbon. Furthermore, the direct me-
thod is recommended when it is known that the sample contains hardly any volatile carbon, and thus
cannot be lost during the purging process:
TOC = NPOC + POC/VOC
(POC/VOC = 0)
TOC = NPOC + 0
TOC = NPOC [mg/l C]
Summing up the advantages of the TOC-Direct Method:
• Quick measurement results are available in only three to five minutes.
• Prevention of impurities from organic substances in the sample vessel, and possibly in the sample
tubes, because adding acid has a cleaning effect.
• Lower consumption of reagents (5% HCl). Only 135 ml are consumed in one day at a measurement
frequency of 12 minutes.
2.1.6 The Measurement Principle of the TConly Method
2.1.6.1 Proceeding
First, the sample is transferred into the sample vessel via the inlet by the help of a peristaltic pump, be-
fore the sample is injected into the ceramic furnace via the injection system.
The sample oxidises completely to CO
2
at 1,200°C in the ceramic furnace. After the oxidation a carrier
gas, which flows continuously through the ceramic furnace, transports the measurement gas to a cooler.
The water vapour produced by oxidation is condensated out by the cooler, and remaining corrosive com-
bustion gasses are then cleaned by the filters. Then the CO
2
concentration is determined in a NDIR de-
tector and output as the TC.
Notice
Depending on the application, hydrochloric acid concentrations between 3 % and 5 %
can be used.
Please contact your local partner or the Technical Support of LAR (Chapter 15 on
page 245) before using other concentrations.
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