Metrohm 2.946.0010, Руководство пользователя

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7 Troubleshooting
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51
Problem Cause Remedy
Pipetting has not been car-
ried out correctly.
￭
The standard additions have to be carried
out by the same person using the same
pipette.
￭
Read up on the correct pipetting in the
manual of the pipette.
￭
Control and recalibrate the pipette.
The standard addition
solution is too old. Prepare a fresh standard addition solution.
Also consider the stability and age of the stan-
dard stock solution.
Standard addition solution
does not conform to the
analyte. Different species of an analyte, e.g. As
III
and
As
V
, can show different sensitivity in a determi-
nation. Therefore, take care that the analyte in
the standard addition solution chemically cor-
responds to the analyte to be determined in
the sample.
The electrode was stored in
water. Solid state electrodes should not be stored in
ultrapure water, since this can affect the condi-
tion and sensitivity of the electrode. For rec-
ommended storage conditions refer to the
respective application documentation.
The electrolyte is too old. Prepare a fresh electrolyte solution. Also con-
sider the stability and age of the reagents used
for the preparation.
The stirrer does not work
correctly. See Stirrer - the stirrer does not rotate .
Curve shape - the
curves show a jump,
a step or a flat line. The potentiostat changes
the current measuring
range during the sweep. In current measuring range Auto , the poten-
tiostat changes to the next higher current
range when the current exceeds 3 times the
applied current range, and to the next lower
current range when the measured current is
lower than 0.05 times the applied current
range.
Change the current measuring range in the
method from
Auto to a fixed range (usually
±1 µA or ±10 µA show good results).
The current measuring
range is too low. The maximum current which can be measured
in a fixed current range is 4 times the selected
current range, e.g. in the ±1 µA current mea-