|
Reliable and proven method
|
| First the mercury contained in
the sample is transformed into the elemental state by addition
of a reducing agent. Subsequently the mercury is stripped with
a gas stream and carried into the optical cell which is made
entirely of fused silica. There the quantitative determination
of mercury is obtained by measuring UV absorption at a
wavelength of 253,7 nm. This analytical technique is commonly
known as "cold vapour atomic absorption spectrometry (CVAAS)",
a method that has proved itself as extremely sensitive and
selective over many years. |
|
| Optimized mercury
detection technique |
|
In contrast to a typical multielement AAS
the AULA is specially designed for elemental mercury. This
allows top performance in analytical applications. 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. |
|
| AULAWIN software: User
friendly operation |
| Handling of the AULA 254 is
not complicated thanks to a software which comes with the
analyzer and has specially been designed for the AULA system.
|
|
| Low analysis
costs |
| The AULA 254 is economical.
Reagent costs for 1000 analyses are approximately
20$. |
|
| High sample
throughput |
| No long purging or rinsing
procedures even when samples with high concentrations are
analyzed. The typical duration of one full measurement cycle
is 100 ... 280 seconds (depending on the concentration).
|
|
| Performance of
measurement |
|
Measurements of up to 10 calibration
standards and up to 53 samples and check standards are carried
out fully automatically in one run. Standards and samples are
filled into glass vials (10 ml) and positioned on the auto
sampler turntable. Reagent solution for mercury reduction
(tin-II-chloride or sodium tetrahydroborate) and rinse
solution (reagent water) are filled in the corresponding
tanks. Then the stripping gas flow is adjusted and measurement
is started by pressing a key.
The absorbance signal is displayed in real
time on the screen. The measurement cycle can be interrupted
by the operator at any time for selecting any sample position
to be measured next. Results are directly displayed on the LC,
reported to a PC and printed out. |
|
| Minimized memory
effects |
| Mercury vapor has a general
tendency to adsorb on surfaces causing a memory effect. This
undesirable effect has been minimized by using selected
materials for sample and stripping gas conducting components
and by heating the optical bench. In addition to this the AULA
uses a thermoelectric dehumidifier to remove water vapor
before the gas enters the optical cell. By this the use of
chemical dryer tubes which always have a much larger surface
is avoided. This also allows a high sample throughput. Even
samples with concentrations in the upper measuring range do
not produce a carry over to the following sample. |
|
| Safety for the
user |
| The mercury cannot escape into
the working environment, as any free mercury is collected in a
sulfurized activated carbon filter. A message appears on the
control panel if the cartridge needs replacement.
|
|
| Data
storage |
|
The results of the analyses together
with the data necessary for quality assurance (date,
time, name of analyst, sample number, calibration data,
instrument settings) are stored in the computer. They
are available at any time, and a print-out of this data
is also possible. Check standards guarantee a high level
of reliability of the analytical results.
Figure: Precision of AULA 254
measurements . |
|
| |
| |
|
| Automatic protective
system cleaning |
| The instrument automatically
interrupts the measurement if samples with mercury
concentrations exceeding the measuring range are detected. In
this case the system is immediately cleaned. |
|
| AULA 254 Technical
Specifications |
| Measuring principle: |
UV-Absorption, cold vapor technique (CVAAS)
|
| Wavelength:
|
253,7 nm
|
| UV source:
|
electrodeless low-pressure mercury lamp
(EDL), temperature-controlled |
| UV
detectors: |
silicon,
UV-enhanced, temperature controlled |
| Stabilization method: |
double beam
(reference beam) method |
| Optical
cell: |
fused silica
(Suprasil), approx. 23 cm long |
| Optical cell
heating: |
approx. 50°C
|
| Gas
dehumidifier |
thermoelectric principle (Peltier
effect) |
| Pump:
|
3-channel
peristaltic pump with stabilized fixed speed
|
| Detection
limit: |
< 80 pg
Hg |
| Measuring
range: |
low range:
0.01...5 µg/L
high range: 0...50 µg/l |
| Measuring
cycle: |
approx. 100-
280 seconds, depending on concentration |
| Zero drift
compensation: |
Auto zero
before each measurement |
| Carrier gas:
|
argon,
alternatively nitrogen, ca. 4 l/h |
| Autosampler
type: |
Turntable,
random access, with rinsing station |
| Autosampler
capacity: |
53 positions
for 10 ml sample vials |
| Operating
temperature: |
10°C - 35°C
|
| Power
Supply: |
230/115 V~;
50/60 Hz; (+10% / -15%) |
| Power
consumption: |
max. 100 W
|
| Data output
interface: |
serial (RS
232) for PC connection |
| Dimensions:
|
Auto sampler
/ reaction unit: 345 x 295 x 545 mm (WxHxD)
Photometer: 450 x 150 x 350 mm (W x H x D)
|
| Weight:
|
approx. 14
kg | |
