Metrohm 7010 TOC, User Manual

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7010 TOC ANALYZER ­ USER MANUAL
16
The sample is pumped by a peristaltic pump
(08)
to the inorganic scrubber
(14)
afterd mixing with acid (usually phosphoric acid) pumped by a second peristaltic
pump
(10)
.
The inorganic removal is performed using ambient air provided by an internal air
compressor
(10)
. This first process lowers the pH of the sample and convert the
carbon carbonates to carbon dioxide. The carbon dioxide dissolved in water is then
driven out by the sample to the vent using compressed air.
The acidified and sparged sample is then pumped from the scrubber bottom to the
UV reactor
(06)
by the resample pump
(07)
, after mixing with a strong oxidizing
agent (usually sodium persulfate) pumped by a dedicated peristaltic pump
(09)
.
The presence of a strong oxidizing agent combined with high level UV radiation
causes the oxidation of organic compounds. The produced carbon dioxide is
driven to the gas­liquid separator
(12)
. The liquid sample is drained off while the air
that containing carbon dioxide goes to the infrared analyser
(13)
, passing in
sequence through a glass condenser
(02)
, gas drier tubing
(05)
and a halogens
filter
(02)
. These devices are present to prevent condensation and corrosion inside
the stainless cell of the IR. The carrier gas used for the oxidation and detection
stages is generated by a second internal air compressor
(09)
and is passed
through a sodalime filter
(05)
. The carbon dioxide free gas passes through a
pressure regulator
(04)
, a capillary tubing and a digital flowmeter
(08)
to reach
finally the UV reactor. All these devices are necessary to guarantee high precision
and stability of carrier gas flow as well as to control and be able to display the flow.
2.2 O
PERATING PRINCIPLE
The water from the sample source (directly from the sampling point or through the optional
filtration unit) is fed to a sampling device mounted on the external left side of the analyzer
(ref. page 19)
. This device drains the sample excess and is equipped with a level sensor
to check the sample presence. This device allows a good sample refreshment and will put
the analyzer in stand­by condition in case of loss of sample.
SODIUM PERSULFATE
CLEANING
ACID
SAMPLE