Analytical Problems; Autosampler - Metrohm 889 IC Sample Center Basic Manual

6.2 Analytical problems

6.2 Analytical problems
6.2.1

Autosampler

Problem
The reproducibility
does not correspond
to the specifications.
A peak which is too
high occurs with a
blank.
There is no injection.
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Analytical problems such as poor reproducibility and carry-over can occur
in any chromatography system. The cause is usually difficult to find. First
of all, you should attempt to determine whether the problem is caused by
the Autosampler or another component of the system.
Take into consideration the fact that analytical problems can also be
caused by external influences such as temperature or light-sensitive sam-
ples. Make sure that the application was able to be performed previously
without problems and that no changes have been made to the system.
Some causes and possible solutions for analytical problems are listed
below. Contact your service point for additional help.
Cause
There is air in the flow
path.
There is a dead volume in
the tubing connections.
The sample properties and
the hardware do not corre-
spond.
The blank is contaminated.
The cause is not clear.
The flow path is blocked.
￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
Remedy
Rinse the needle on the inside and outside.
Reinstall the connections with new pressure
screws.
Check the hardware:
Rinse the needle on the inside and outside.
￭
Valve — Replace the rotor with another
￭
type.
Capillary connections — Replace capillary
￭
between Autosampler and column or use
another washing solution.
Use a new blank.
￭
Do not fill the sample vessel completely in
￭
order to avoid contamination of the air
needle.
Examine the problem more closely by varying
the washing solution.
1. Loosen the needle from the valve.
2. Clean the needle.
3. If washing solution is flowing out of the
injection port, check the needle. If no
washing solution is flowing out of the
injection port, remove the buffer tubing
from the valve.
889 IC Sample Center Basic