Function and design
HS 55 (Batch Mode)
18
3.2.5
Type plate
The type plate is located on the rear of the device. The type plate contains the following
information:
¡
company name and complete address of the manufacturer
¡
device designation: type designation and trade name
¡
model and serial number
3.3
Measuring process
You can start the measurement either by pressing the "Start" button on the Hg/hydride
system or via the control and analysis software of the AAS.
Start the measurement immediately after you have filled a new sample into the reaction
beaker and attached the reaction beaker in a gastight manner. The Hg/hydride system
first purges the reaction beaker with argon to remove any air. After a certain waiting
time, the software registers the zero value (AZ = Auto Zero).
After the baseline adjustment, the hose pump starts pumping reduction agent into the
reaction beaker. After a short time, the purge flow starts: the carrier gas argon trans-
ports the metal hydrides formed or the elementary mercury to the AAS. Atomic vapor
forms in the quartz cell or the graphite tube furnace, respectively. The metal hydrides
decompose due to collisions.
In mercury detection, the pre-wash time and the AZ waiting time are omitted to prevent
the highly volatile mercury from being expelled from the sample too early. The zero
value is determined over a period of 2 s instead of 4 s.
Measuring process with enrich-
ment
Before a sample is supplied to the atomizer of the AAS device, the Hg/hydride system
enriches mercury from one or more samples on the gold collector. The gold collector re-
leases the mercury again during bake-out. With the subsequent cooling, the Hg/hydride
system prepares the gold collector for the next measurement.
Operation times
In the control and analysis software, you can define the following operation times in a
method for the Hg/hydride system:
Option
Description
Prewash time
Time for purging the beaker with argon before the reaction (for hy-
dride formers)
The pre-wash time is used to expel air to prevent an oxyhydrogen re-
action during the subsequent reaction.
Pump time
In this time, the reduction agent is pumped into the beaker in order to
start a reaction.
AZ wait time
Time directly preceding the baseline adjustment (AZ = auto zero).
Wash time
The wash times are needed to transport the reaction gas with the ar-
gon flow. The transport paths can be graphically displayed.
Heat. time collector
During this time, the heater runs to release the enriched mercury
from the gold collector.
Cool. time collector
During this time, the gold collector is cooled to make it ready for the
next enrichment.
Graphical display
To open the graphical display of the gas paths, click on Plot in the Method |Hydride
window. The window displays the operations that run partially simultaneously during
the individual phases of the measurement.
