16
MD100_4 10/2014
GB
General notes
Guidelines for photometric measurements
Vials, caps and stirring rods should be cleaned thoroughly
1.
after each analysis
to prevent
interference.
The outside of the vial must be clean and dry before starting the analysis. Clean the outside
2.
of the vials with a towel to remove fingerprints or other marks.
Zero calibration and test must be carried out with the same vial as there may be slight
3.
differences in optical performance between vials.
The vials must be positioned in the sample chamber for zeroing and test with the
4.
mark
on the vial aligned with the mark on the instrument.
Always perform zeroing and test with the vial cap tightly closed. Only use the cap with
5.
a sealing ring.
Bubbles on the inside wall of the vial lead to incorrect measurements. To prevent this,
6.
remove the bubbles by swirling the vial before performing the test.
Avoid spillage of water into the sample chamber because this can lead to incorrect test
7.
results.
Contamination of the transparent cell chamber can result in wrong readings. Check at
8.
regular intervals and – if necessary – clean the transparent cell chamber using a moist
cloth or cotton buds.
Large temperature differences between the instrument and the environment can lead to
9.
errors – e.g. due to the formation of condensation in the cell chamber or on the vial.
To avoid errors caused by stray light do not use the instrument in bright sunlight.
10.
Prior to measurement ensure that the sample is suitable for analysis (no major interferences)
11.
and does not require any preparation i.e. pH adjustment, filtration etc.
Correct filling of the vial:
Correct position of the vial (Ø 24 mm):
