Teledyne 6700-C Total Organic Carbon Analyzer (Hi-Temp Combustion version) - Manual (Page 17)

High Temperature Combustion Operational Theory
Teledyne Analytical Instruments 17
Operational Theory
2.1 Measurement Principle
Refer to Figure 2-1.
The Injector is connected with all possible flow paths and separated
from sample and reagent liquids by a 10 ml volume loop. One end of the
volume loop is connected to the injector, the other is connected to the
center port of a 10 port Rotary Valve.
A typical sequence of events for the injection unit for measurement
of TOC is as follows:
The Rotary Valve will be engaged, opening a flow path to the drain
line of the analyzer. The Injector is then sent to the home or empty
position.
The DI Valve is turned on and a small amount of DI is then picked
up by the Injector. The DI Valve is then turned off and the Rotary Valve
is turned to the Acid Port where the Injector pulls a small amount of acid
into the loop. The Rotary Valve is then turned to the sample port and
sample is pulled into the loop. The Rotary Valve is turned to the Sparge
Port and the Injector then pushes the sample and acid to the sparger
through the Sparger Port, where the pH is lowered to approximately 2.0
and inorganic carbon is removed.
After the sparge time is completed, the Injector pulls the inorganic
free sample volume from the sparger. The Rotary Valve is then turned to
the Reactor Port. The Injector pumps the sample into the reactor at a
flow rate of one (1) drop in approximately seven (7) seconds.
The sample is oxidized in the High Temperature Furnace where
organic carbon is converted to CO
2
and the gases are directed to a cooler
condenser where excess water is removed, and then on to the NDIR
where the CO
2
is measured and TOC is determined. The gases are then
passed to vent.