Hach-Lange DR 6000 User Manual - Manual (Page 62)

62
Standard programs
Select Carousel 1 inch square to perform a series of
measurements in 1-inch square cells with an optional
carousel insert.
Select Carousel 1 cm square to perform a series of
measurements in 1-cm square cells with an optional carousel
insert.
Additional information can be found in the Carousel user
manual.
5.4.10 Standard Addition - monitoring/checking results
The accuracy of readings (their correspondence with the actual
concentration of the analyte in the sample) and their precision
(correspondence of the reading results obtained from several
samples containing the same concentration of the test analyte)
can be determined or improved using the standard addition
method
This method (also known as standard-addition or spiking) serves
to detect sample-specific faults:
• The analysis was compromised by substances or
interferences in the sample (sample matrix effect),
• defective measuring device,
• impure reagents.
Method:
Add a defined quantity (concentration) of the substance to be
tested to the sample as a standard solution. The detection rate
(concentration of the added standard solution) should be close to
100 %.
Detection rate =
Reading of successful standard addition
Expanded value after successful standard addition
Detection rate Conclusion
100 %
Probability that the reading results are correct
is high.
≠ 100 %
Assumption: The analysis was compromised
by substances or interferences in the sample
(sample matrix effect)
Test to determine whether a sample matrix
effect is present:
Use distilled water instead of the sample. Add
standard solution as described in the
procedure.
Detection rate Conclusion
100 %
Ions in the sample are
interfering with the
analysis, causing false
results to be obtained.
≠ 100 % No interference ions.