Hach-Lange LUMISTOX 300 LPV321 User Manual - Manual (Page 18)

LUMIStox 300 Operating Manual Dr. Bruno Lange GmbH
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Page: 18
2.7 Determining chronic toxicity with LUMIS·24·tox
In the context of the luminescent bacteria test, chronic toxicity is the long-term effect of
a sample on luminescent bacteria. The incubation period is therefore 24 hours. The
luminescent bacteria test for chronic toxicity, LUMIS·24·tox (LCK486), also involves the
calculation of an interim value after 30 minutes so that the user can also be provided
with the estimated acute toxicity of the same test solution.
The result of the luminescent bacteria test for chronic toxicity is expressed as a GL or
EC value.
In addition, the built-in photometer function of the LUMIStox 300 can be used to
determine the effect of the sample on the growth of the bacteria. This involves
measuring the optical density (OD) of the bacteria suspension before and after carrying
out the luminescent bacteria test for chronic toxicity with the LUMIStox 300.
Incorrect individual measurements of initial or final luminescence can be annulled
immediately with <C> and carried out again.
Work steps:
1. Prepare and dilute the sample(s).
2. Pipette 1.5 ml sample (dilution) into measuring cuvettes and bring to the correct
temperature in row A of the LUMIStherm. The highest sample concentration
should be positioned on the extreme right.
3. Bring 1.5 ml control solution (2% NaCl solution) to the correct temperature in
position A1 of the LUMIStherm.
4. Reactivate the preserved bacteria as described in the package circular.
5. Pipette 0.5 ml bacteria suspension into measuring cuvettes (2 per sample
dilution) and leave to stand for 15 minutes in rows B and C of the LUMIStherm to
acquire the correct temperature.
6. For the OD measurement, mix 1 ml bacteria suspension and 1 ml 2% NaCl
solution in a measuring cuvette.
7. Select evaluation mode <OD> on the LUMIStox 300 and measure and record (or
print) the OD of the bacteria suspension against 2% NaCl solution.
8. Select evaluation mode <chrn> on the LUMIStox 300.