Hach Eclox, User Manual

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Section 11 Luminescent Bacteria Toxicity
Test ISO 11348 part 3
The Luminescent Bacteria Toxicity (LBT) Test uses the luminometer. Before doing
the procedure, read section 3.1, Overview on page 15 and do the procedures in
section 3.2, Prepare the luminometer for use on page 16 .
This chapter describes the LBT Test measurement luminescence procedure and
contains the procedure steps. Use the LBT Test measurement luminescence
procedure if the test needs to be done according to ISO 11348 part 3. The Eclox
LBT Test measurement luminescence procedure meets the criteria of validation of
ISO 11348-3.
11.1 Overview
The test criterion is luminescence which is measured after a contact time of 15 or
30 minutes (optionally 5 minutes at 15 °C) taking into account a correction factor
(fK). The correction factor is a measure of intensity change of control samples
during the exposure time (refer to the ISO standard procedure).
The luminometer measurements are in relative light units. The luminometer
measurements are used by the LUMISsoft computer program or custom made
calculations to calculate percent inhibition, LID, EC20 and EC50 values.
• Percent inhibition —the percentage of light made by the bacteria that is inhibited
by the sample. The higher the percentage inhibition of the light emission, the more
harmful the sample is to the bacteria and the higher the toxicity level of the
sample.
• LID —first dilution value of a sample that causes less than 20% inhibition. The
higher the LID, the more harmful the sample is to the bacteria.
• EC20 or EC50 —the concentration of a sample that causes exactly 20 or 50%
inhibition. The lower the EC-value, the more harmful the sample is to the bacteria.
The linear measuring range is between 10% and 90% inhibition. Refer to ISO
11348 for more detailed information on the Luminescent Bacteria Toxicity Test.