Endress+Hauser Analytik Jena Multi X 2500, Руководство по эксплуатации

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multi X 2500 Function and layout of the multi X 2500
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3 Function and layout of the multi X 2500
3.1 Principle of operation
The multi X 2500 allows determining organically bound halogens in a sum parameter
analysis using the AOX, EOX or POX method. These methods generally comprise three
main steps which basically only differ in the first step which is the sample preparation.
1.
Enrichment of organic halogen compounds and separation of inorganic
halogenides:

by adsorption on activated carbon (AOX),

by extraction with organic solvents (EOX), or

by stripping in the carrier gas stream (POX).
2. Mineralization of the organic compounds:
The loaded activated carbon or an aliquot of the extract or the loaded carrier gas is
introduced to the reactor, pyrolized in the argon stream if applicable and
combusted in an oxygen stream at a temperature of at least 950 °C into hydrogen
halide, carbon dioxide and water:
R-X + O
2
→ HX + CO
2
+ H
2
O (1)
R = residual hydrocarbon
X = Cl, Br, I
Oxygen and argon are both used as carrier gases at the same time. The pyrolysis
gases are dried with concentrated sulfuric acid.
3. Detection of the hydrogen halides (HCl, HBr, HI) via micro-coulometric titration
(HF is not determined).
This process will take place in an acetic acid medium in accordance with the
following reaction equation (2):
Ag
+
+ X
- →
AgX (2)
The silver ions needed for halide precipitation are produced electrolytically on a silver
anode. When the halide which was produced during combustion has been decomposed
the concentration of silver ions will rise in the electrolyte. This point in the process is
called the titration end point. The titration end point is determined using a pair of
polarized indicator electrodes (biamperometrically) or a potentiometric indicator
electrode. Based on the Faraday law, the amount of charge used until the analyte is
completely decomposed is used to calculate the amount of halides. The result of this
calculation is indicated in relation to chloride.
The sample preparation described under item 1 is omitted when determining the total
chlorine content (TX). The samples are introduced to the analyzer directly and
combusted there. The halide ion content is determined in relation to chloride.
TX determination