Metrohm 743 Rancimat - Manual (Page 175)

￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭ 6 Troubleshooting
743 Rancimat ￭￭￭￭￭￭￭￭ 167
Problem Cause Remedy
The induction time
is longer/shorter
than expected. The temperature is not
selected correctly. ￭ Ensure that the correct method for the
determination has been selected.
￭ Check that Temperature and Delta T
have been specified correctly in the
method (see Chapter 4.5.2.1, page 60).
See also: The induction
times are not reproducible
for multiple determina-
tions.
The stability time is
longer/shorter than
expected. Delta Kappa is not defined
correctly. Ensure that the value of Delta Kappa defined
in the method is correct (see Chapter 4.5.2.2,
page 64).
See also: The stability times
are not reproducible for
multiple determinations.
See also: The induction
time is longer/shorter than
expected.
The measurement
curves are extremely
noisy. The air supply for the
measuring solution is direc-
ted to the conductivity
measuring cell. Loosen tubing adapter (5- 11 ) on the measur-
ing vessel cover, turn the PTFE tube (5- 17 ) in
such a way that the air is no longer directed to
the measuring cell and fix in this position.
Gas bubbles adhere to the
conductivity measuring cell
during measurement. ￭ Ensure that the measuring cell is clean and
free of fat. If necessary, clean thoroughly
(see Chapter 4.6.5, page 83).
￭ In some cases ultra pure water contains a
large proportion of dissolved air which
escapes during measurement. In this case,
degas the ultra pure water before the
measurement for 5 to 10 min in a vacuum.
During the measurement,
sample evaporates in the
reaction vessel and con-
denses in the measuring
vessel. This results in con-
tamination of the conduc-
tivity measuring cell, which
in turn promotes adher-
ence of gas bubbles. ￭ Keep the measuring time as short as possi-
ble, by about 4 to 6 h. The induction time
can be reduced by about half by increasing
the temperature by 10 °C.