Eicom ENO-30, User Manual

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12. Reduction Column (NO-RED)
12-1. Structure and Maintenance
NO
3
-
is reduced to NO
2
-
by the reduction column, but NO
2
-
is not reactive with cadmium. The
reduction column contains cadmium and reduced copper which are consumed by the delivery of
solvent. To fill the space made by consuming of cadmium/copper, tighten the screw to clockwise
(arrow in figure) before analysis once a day. If you do not tighten this screw, shape of the peak
will become broader.
12-2. Timing to Exchange
The reducing ability is measured by a standard solution. When the NO
3
-
peak height becomes
extremely low, please replace the reduction column. After attaching a new reduction column,
please inject the standard solution. The life span of the reduction column is around 1-3 months.
12-3. Damage
The reduction column loses its ability in following conditions. Please avoid to injecting these
samples.

AVOID injecting metals with lower ionization tend
ency than the reducing column’s
cadmium. If a high concentration of such a metal is injected, cadmium in the column will be
coated by the metal.
Example: 1mM Hg
2+
, Fe
3+
, Nitrosoprusside.

AVOID injecting high concentration of thiol compounds. If a high concentration of a thiol
compound is delivered to the reduction column, the compound will be adsorbed on the
surface of the cadmium..
Example: 1 mM Dithiothreitol (DTT)

AVOID injecting strong acid. Strong acid in the samples can prevent the reduction
reaction.. However, weaker acids in the sample will be diluted by the carrier, and therefore
the will not interfere with the reduction.
Example: 1 mM Asparatic acid
/Ringer’s solution (pH4.5), High concentration of HCl,
H
2
SO
4
, H
2
PO
4
, CH
3
COOH