Hach-Lange DR 6000 User Manual - Manual (Page 63)

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Standard programs
Measures to identify other interference factors:
Checklist:
1. Check if the procedure is completed correctly:
a. Are the reagents added in the correct order?
b. Is enough time allowed for colour development?
c. Is the correct glassware in use?
d. Is the glassware clean?
e. Does the test require the sample to be at a certain
temperature?
f. Was the pH of the sample in the correct range?
g. Is the pipette volume correct?
2. Check the reagents. Repeat the standard additions using
fresh reagents.
If none of these measures resolves the problem, please contact
the manufacturer.
5.4.10.1 Complete a standard addition
Carry out the standard addition in accordance with the
corresponding procedure.
There are two different methods:
Maximum Volume (standard addition)
A defined volume of a standard solution of known concentration
is incrementally added to a previously tested sample and the
sample is newly measured after every standard addition.
Sample volume:
A defined volume of a standard solution of known concentration
is added to the volume of sample specified in the procedure and
the sample is measured after each addition. In most cases three
different standard solutions are prepared and the procedure is
repeated for each of them.
Note: The units and chemical forms used for the sample are used for the
standard solutions. Be careful to make sure that to use the correct units
for subsequent entries.
Detection rate Conclusion
100 %
The originally used reagents were defective.
Check the standard solution:
Repeat the standard addition procedure with
a freshly prepared standard solution and
distilled water!
Detection rate Conclusion
100 %
The originally used
standard solution
was deficient.