Hach-Lange LUMISTOX 300 LPV321 User Manual User Manual
Page 14
LUMIStox 300 Operating Manual
Dr. Bruno Lange GmbH
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Page: 14
2.5 Determining the GL value
The GL value, as referred to in DIN 38412 L34/341, gives the dilution level at which a
sample causes less than 20% inhibition in the luminescent bacteria test. DIN prescribes
the measurement of a sample dilution series by means of double determinations after
an incubation period of 30 minutes. The record printed by the LUMIStox (e.g. on a Dr.
Lange LD 500 printer) corresponds to the DIN documentation of a luminescent bacteria
test. With a LUMIStherm, the control solution and 9 samples (dilutions) can be
measured in one sequence in conformity with the DIN standard.
Incorrect individual measurements of initial or final luminescence can be annulled
immediately with
Work steps:
1. Prepare and dilute the sample(s).
2. Pipette 1.5 ml 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.
Select evaluation mode
<480> for LCK480, on the LUMIStox 300.
7. If necessary enter the initial settings for the test into the LUMIStox 300.
8. Measure the initial luminescence of the bacteria at the specified time intervals.
9. Immediately after each measurement, pipette 0.5 ml control or sample dilution from
the corresponding position in row A into the bacteria suspension in row B or C.
10. Wait for the residual incubation time to elapse.
11. Measure the final luminescence of the control and test solutions at the specified
time intervals and record or print the results.