XD 7500
Operation
139
ba77191e01 - 71310060
04/2018
4.15.4
Checking the sample for matrix influence (SCheck)
The
SCheck
is used to check if the photometric determination is disturbed by
other substances present in the sample (sample matrix). The SCheck is done
through spiking.
The ValidCheck
®
multi-standards include, in addition to a normal, also a
more concentrated standard solution for spiking the sample. Since its param-
eters are already stored in the photometer, the execution of the test for the
sample matrix is simplified. The SCheck can be carried out immediately. The
volumes required for the sample and standards
are displayed on the screen. The SCheck is then carried out with a single
spike.
For the SCheck with individual standard, you can insert one or two spikes
yourself depending on the measured value and measurement range end.
SCheck through
spiking
For the SCheck by spiking, the photometric determination is repeated after a
defined amount of analyte, which should be determined again, has been
added to the test sample in the form of standard solutions.
From the added quantity of analyte (spiking), the nominal value for the deter-
mination is calculated under the assumption that there are no disturbing influ-
ences in the sample matrix. After the photometric determination the
measured value is compared to the nominal value expected and the recovery
rate is calculated. A matrix disturbance is likely if the recovery rate is less than
85 % or more than 115 %.
Practical instruc-
tions
After evaluation of the measurement value of the sample, the photometer
proposes a spiking for the SCheck with suitable volumes of sample and
standard.
You can change the suggested values of the volumes for the sample and
standard. The photometer checks your entries and informs you of errors
(e.g. if a nominal value is outside the measuring range of the test).
The associated concentrated nominal value is displayed for each spiking.
To be able to reliably recognize matrix effects by spiking, the volume
increase after spiking should be small.
You can carry out the SCheck with up to two measurements with different
spiking volumes.
Prepare all measurement solutions in parallel at the beginning of the mea-
surements.
With activated user management, only users of the user group
Administrator
may change the settings for DeviceCheck tests.
The DeviceCheck check can be performed by any registered
user.
