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Section 3
3.1 Unpacking
3.2 Overview
3.3 Principle of Operation
6
General Description
Remove the analyzer from its shipping carton and inspect it for any damage. If
damage is evident or the shipment is incomplete, please contact the Customer
Service Department, Hach Company, Loveland, Colorado for instructions. The
toll-free number is 800-227-4224.
The 9186 Oxygen Scavenger Analyzer
single-channel industrial analyzer that measures hydrazine or carbohydrazide in
boilers and other applications that require monitoring of oxygen scavengers at the
ppb and ppm levels.
This instrument uses a 3-electrode amperometric method to
measure concentration.
The 9186 Analyzer continuously measures the amount of oxygen scavengers,
dissolved hydrazine, and carbohydrazide in water. The measuring principle is
based on the electrochemical method of 3-electrode amperometry.
A polarization voltage (+480 mV) is applied between a platinum anode (working
electrode) and a stainless steel cathode (counter-electrode). The oxygen
scavenger is oxidized at the surface of the working electrode and the resulting
current is directly proportional to the oxygen scavenger concentration in the range
of 0 to 500 ppb N
H
(Figure
2
4
The reaction is enhanced in an alkaline environment, the sample is conditioned
before it enters the measuring cell. The sample is conditioned to pH ≥ 10.2 by
adding diethylamine, monoethylamine, ammonia, or diisopropylamine through a
Venturi tube. A sensor integrated to the measuring cell provides temperature
compensation.
The chemical reaction is as follows:
–
→
N
H
4OH
N
4H
O
+
+
2
4
2
2
The anode-cathode potential is kept constant with respect to a third electrode
(reference electrode, Ag/AgCl). This avoids interference effects resulting from
variations in water composition that appear when using the 2-electrode system.
At 480 mV, the cell current is linearly proportional to the hydrazine concentration
(Figure
4).
(Figure 1
and
3).
–
4e
+
Figure
2) is an on-line,
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