Data Security
In accordance with the requirements, methods can be
validated and checked. Most statistical methods can
be easily implemented and are supported by the Metrodata
IC Net software: determining blanks, spiking, reproducibility,
recovery rate, variability of the retention times, etc.
To check the present measurements, four different
volumes – 500, 1000, 1500 and 2000 µL –
were preconcentrated and a three-fold determination
carried out on each. The blank value was determined
and subtracted. The data was then used to check the
linearity and reproducibility of the analysis. Metrohm
inline calibration with fixed sample loop, the use of
only one standard solution and the extraordinary precision
of the 800 Dosino provide excellent results; both under
normal laboratory conditions and under the rough conditions
prevailing in the power plant turbine room.
Carryover
Samples, standards, regeneration and transfer solutions
partly use the same tubing within the IC system. Particular
attention has been given to keeping carryover within
the system negligible.
Air bubble: As simple as
effective: a defined volume of air is aspirated between
different liquid portions and transferred through the
tubing system. Even this simple step significantly reduces
carryover.
Rinsing the sample needle:
In order to prevent carryover caused by the sample needle,
it is assigned a special position by the sample changer
and thoroughly rinsed both inside and out with a freely
selectable rinsing solution. If the risk of carryover
is insignificant, it is sufficient to rinse the needle
at one of the three special positions on the sample
rack. Liquid handling during the rinsing process is
carried out by the 800 Dosino.
Rinsing the flow path: The
800 Dosino is used to rinse the complete flow path of
the system that comes into contact with the sample.
This is normally done with ultrapure water, but solvent-water
mixtures can also be used as the whole system is solvent-resistant.
The longer the rinsing with ultrapure water, the lower
the carryover from sample to sample. Even in normal
operation with rinsing times of two minutes, the carryover
between two samples is below 0.3%. If ultrapure water
is injected a second time then the carryover is less
than one part per thousand.
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