Eicom ENO-30, Руководство пользователя

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3 | P a g e
2. Overview
2-1. Principle of Measurement
The ENO-30 is a high sensitivity instrument for measuring nitrite and nitrate ion level in
biological fluids. This is achieved by combining a colorimetric diazo coupling method (Griess)
with the advantages of HPLC.
After the sample is injected it is filtered by the guard column. Then the separation column
interacts with the ions in such a way that they flow though the column at different rates. Nitrite
exits the column first, and then some minutes later, the Nitrate leaves the column. The NO
2
-
and
NO
3
-
next flow into the reduction column made is cadmium and copper.
Inside the reduction column, the NO
3
-
is reduced to NO
2
-
through a reaction with the cadmium
and reduced copper. The NO
2
-
that exited first will not react. So now there are two Nitrite peaks,
the first is from the Nitrite in the sample and the second is from the Nitrate in the sample. Both
are mixed with a Reactor solution supplied by a second pump at a 3-way joint, and then flow
into a reaction loop. This gives time for the reaction come to the right temperature and complete
formation of a light absorbing diazo compound that can measured at the detector.
In the detector cell, 540 nm (green) light passes through the sample, and the absorption is
proportional to the amount of diazo compound, and thus to the amount of Nitrite or Nitrate.
The response of the detector is transformed to a voltage which it generates at the CPU terminal.
The time/voltage change is traced by a data processor such as the optional Eicom EPC-700. By
comparing peak area or height shown on a chromatogram with a standard one, the exact
concentration Nitrite and Nitrate can be calculated.