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4.2.3.5 TN Analysis
In BioTector, the Total Nitrogen (TN) analysis does not require an additional oxidation cycle because
BioTector’s oxidation process breaks down all bound, organic and free nitrogen compounds present in the
sample into Nitrate (NO
3
-
), which exists as an ion in the oxidized sample liquid in the BioTector reactor.
1. The oxidized sample liquid is discharged from the reactor and collected in the oxidized sample catch-
pot/cleaning vessel. See figure 5, which shows the typical liquid phase analysis layout of a TOC TN
analyzer.
2. This oxidized sample is brought to the Dual Cell Photometer Module (DCP Module) and placed into
the TN Measuring Cell by the Nitrogen Pump (N Pump). The DCP Module consists of a TN
Measuring Cell, a Xenon Flash Lamp light source, two light beam splitters, two detectors and two
optical filters. See figure 6, which shows the layout of the DCP Module below.
3. The Xenon Flash Lamp is turned on. Two of the detectors, which are the signal and the reference
detectors, are used during the TN measurement. The primary TN measurement is carried out at
217nm (signal wavelength), where NO
3
-
absorbs UV light. In addition to the primary measurement, a
secondary reference measurement is carried out at 265nm (reference wavelength). The measured
TN result is displayed and sent as a 4-20mA output.
4. When the TN measurement is completed, the oxidized sample is pumped back into the Oxidized
Sample Catch-Pot/Cleaning Vessel. The oxidized sample liquid is used as a sample tube cleaning
liquid during the Reverse Wash Cleaning Cycle.
5. At regular intervals, an automatic cleaning of the TN Measuring Cell, chambers and lines are carried
out, using the TN Cleaning solution. When the TN cleaning cycle is completed, deionised water (DI
Water) is used to wash the cleaned chambers and lines.
6. At regular intervals, an automatic reference reading on DI Water is also carried out at the same signal
and reference wavelengths used for the TN measurement.
BioTector analysis types are optional features. In order to be able to utilize TN
analysis type in BioTector, the system must be built with this option. For instance if a
system is built with the TIC & TOC and TN analysis options, this system cannot be
used to measure the TC and VOC content of the sample. In order to measure any
additional parameters in a system, mechanical changes and modifications in system
configuration and software will be required.
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