First the
mercury contained in the sample is stripped with an air stream and sucked into
an optical cell made of fused silica. There the quantitative determination of
mercury is obtained by measuring UV absoption at a wavelength of 254 nm. This
method is commonly known as the "cold vapor atomic absorption spectroscopy
(CVAAS)"
method.

In
contrast to a typical multielement AAS the LabAnalyzer 254 is specially
designed for elemental mercury. This allows top performance in analytical
appliacations. The use of a specially developed highly stable mercury lamp in
connection with thermostat-controlled UV sensors results in a detection limit
of a few ppt of mercury.
Memory
effects are minimized and a high sample throughput is possible thanks to
specially selected materials for sample gas conducting components and heating
of the optical bench.
The
LabAnalyzers 254 is operated with a waterproof membrane keypad and a graphic LCD.
Handling is extremely easy. The LabAnalyzer 254 does not require auxiliary
gases. The carrier gas flow required for the analysis is generated by a
built-in membrane pump which is maintenance-free and has a long service life.
The sample
is pipetted into an extractor and mixed with 0.5 ml of reducing agent, for
example tin-II-chloride solution. The extractor is then connected to the
LabAnalyzer 254 and the measurement is started by pressing a button. After 60
to 90 sec the result appears on the display and the device is ready for the
next analysis. The system does not need to be purged, and the zero point is
calibrated automatically before every measurement (auto zero).
The mercury
cannot escape into the working environment, as any free mercury is collected in
a sulfurized activated carbon cartridge. If the cartridge needs replacement a
message appears on the control panel. The analyzed sample no longer contains
any mercury.
Even with
high concentrations no lengthy purging time is required. After every
measurement a zero calibration is carried out automatically (auto zero). The
typical duration of a measurement including purging is 60 to 100 sec. over the
entire measuring range.
During the
entire measurement the measuring signal is continuously displayed on the
graphic display. An acoustic alarm is sounded to indicate the end of the
measurement. In addition to the measurement signal curve over time, the peak value
and the mercury concentration are indicated.
Together
with the data necessary for quality assurance the results of the analyses are
stored in the RAM of the built-in computer. They are available at any time, and
an automatic print-out of this data is also possible.