4 | General Information
7070iX TRO Analyzer
Intended Use
The Thermo Scientific Orion™ 7070iX Total Residual Oxidant
Analyzer is an Iodometric Measurement System designed for
on-demand measurement of total residual oxidants in
process water, cooling water or waste water in the range from
0.001 to 15 ppm. This analyzer model is intended to use for
water analysis only.
Principles of Operations
The Orion 7070iX Total Residual Oxidant (TRO) Analyzer is an
on-demand instrument that provides a TRO measurement.
The analyzer initiates the analysis mode when sample flow is
present. When no sample flow is present, it does not
consume reagent and can support a significant reduction in
the analyzer maintenance. The maintenance and calibration
cycle required for the Orion 7070iX Total Residual Oxidant
Analyzer is 80 Total hours of active operation.
The chemistry employed in the analyzer is the EPA approved
iodometric method for total residual chlorine, in which iodide
together with an acid reagent is added to the sample to react
with and convert all chlorine present to iodine. The formed
iodine is sensed directly by the combination of solid-state
electrode. In the Orion 7070iX Total Residual Oxidant
Analyzer, a portion of the main sample water stream is drawn
and introduced to the flow channel where the chemical
reagent is added to convert all TRO to iodine. The reacted
solution is measured by the TRO sensor in the flow cell.
A general nonspecific description of the iodometric reaction
for total oxidants is given as:
Ox
2
+ 2I
-
-> I
2
+2Ox
-
where:
Ox
2
is total oxidant, such as total chlorine or a combination of
oxidant species.
I
-
is iodide
I
2
is iodine
The concentration of iodine is equal to the concentration of
oxidant before reaction.
The TRO Sensor is a potentiometric combination sensor
containing a platinum (redox) sensing electrode and an iodide
reference electrode. The combination voltage (potential, E)
generated between the sense and reference electrodes is
proportional to the iodine produced in the sample after
reagent addition. The higher the TRO concentration in the
sample, the more iodine is produced and the higher voltage is
generated following the Nernst Equation:
E = E
0
+ S log [l
2
] = E
0
+ S log [Ox
2
]
where:
E
0
is the cell constant in mV at a fixed temperature
S is the sensor slope (approximately 29.6 mV / decade at
25 °C by theory)
[l
2
] is the iodine concentration (ppm)
[Ox
2
] is the total residual oxidant concentration (ppm)
After suitable calibration, the measured voltage E is converted
by the analyzer to read directly as TRO in ppm. The analyzer
detects TRO using an electrochemical process, which is
affected by the temperature of the sample. The sensor
response in the Orion 7070iX Total Residual Oxidant Analyzer
is dependent upon the sample temperature. In the Orion
7070iX Total Residual Oxidant Analyzer, sample temperature
is measured continuously in the flow cell and the calculated
TRO is adjusted to reflect the response which would result at
the calibration temperature. This software adjustment ensures
optimum accuracy over the sample temperature range.
Orion 7070iX Total Residual Oxidant Analyzer uses software
to tightly control the flow of reagent resulting in elimination of
excess reagent which could cause error due to secondary
species formation.
Location
Personal Protective Equipment Warning: Proper
safety equipment must be worn at all times when
servicing the instrument including proper eye
protection and gloves when working with the
reagent and flow cell section.
NOTICE Indicates a situation which, if not avoided, may
cause damage to the instrument or instruction for
special use.
NOTE
Indicates important information that requires
special attention.
The Orion 7070iX Total Residual Oxidant Analyzer
is not suitable for hazardous location as delivered.
Indoor locations only.
Temperature:
41 - 113 °F / 5 - 45 °C
Relative Humidity:
20% to 85%
Altitude:
0 to 2000 m
Pollution degree:
2
Over-voltage:
Category 2
Mains Supply Nominal:
100 - 240 VAC 50 / 60 Hz
Mains Supply Fluctuations:
±10% of nominal
