LAR Process Analysers QuickTOC purity - Advantages; The Measurement Principle of the TOC-Direct Method (NPOC-Method); Proceeding

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04E3920 User Manual QuickTOC

purity

ATEX 2 15

2 Operating Principle of the Analyser

2.1 Measurement of TOC

LAR | PROCESS ANALYSERS AG

Fig. 2: Measurement Principle of the TOC-Difference Method

2.1.4.2 Advantages

In this method, no volatile organic components (POC / VOC) are expelled from the sample. Because all

particles can be measured, all of the TOC remains in the sample - meaning the TRUE TOC is measured

in this method. With the TOC Difference Method the analyser allows for fast and exact analysis of the

parameters:

• TC

• TIC

• TOC

taking the POC/VOC under account.

Summing up the advantages of the TOC-Difference Method:

• Quick measurement results are available between 2 and 3 minutes.

• The entire TOC is determined (no loss of purgeable/volatile organics).

• High precision of results.

2.1.5 The Measurement Principle of the TOC-Direct Method (NPOC-

Method)

2.1.5.1 Proceeding

In the TOC direct method, the sample is first acidified externally with a strongly diluted hydrochloric acid

before it is moved into the sample vessel. There, CO

-free air (carrier gas) continually flows through the

sample. Because of the low pH value (< 2), the anorganics are removed from the sample and drained

off. At the end of this process, the sample only contains the NPOC (Non Purgeable Organic Carbon).

In the next step, the injection system transfers the sample from the sample vessel to the ceramic furnace,

which then completely oxidises to CO

at 1,200°C.