Metrohm 2.946.0010, Руководство пользователя

Страница: 63 / 81

￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
7 Troubleshooting
￭￭￭￭￭￭￭￭
55
Problem Cause Remedy
Electrode, electrode holder,
electrode cable or poten-
tiostat defective. Run the dummy cell test (see chapter 7.5,
page 66) to verify that potentiostat and elec-
trode cable are working correctly.
Replace the electrode by a new one and
repeat the determination.
No peak - the sam-
ple does not show a
peak, but the stan-
dard addition is ok. The sample does not con-
tain the analyte in ionic
form. A sample preparation has to be carried out to
make the analyte available for the analysis. The
kind of sample preparation depends on the
analytical problem.
The concentration in the
sample is below the limit of
detection. Increase the deposition time (method parame-
ter
Waiting time 1 or Waiting time 2 ).
The sample is too diluted. Use a less diluted or undiluted sample.
No sample was added. Add a sufficient amount of sample and repeat
the determination.
No peak - the sam-
ple shows a peak,
but the standard
addition does not
increase the peak. Wrong standard addition
solution. Verify that the correct standard solution with
the correct concentration of analyte is used.
Standard addition solution
does not contain the ana-
lyte. Verify that the correct standard stock solution
and the appropriate volume was used for the
preparation of the standard addition solution.
In case of doubts prepare a fresh standard
addition solution.
Concentration and/or vol-
ume of standard addition
too small. Follow the recommendations in Chapter 7.1.3
Quantification (page 46) to adapt volume
and/or concentration of the standard addition.
Standard addition solution
not stable or 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 concentration in the
sample is too high. Adapt the volume and/or concentration of the
standard addition or dilute the sample. Con-