Hach-Lange LUMISTOX 300 LPV321 User Manual - Manual (Page 35)

LUMIStox 300 Operating Manual Dr. Bruno Lange GmbH
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Page: 35
4.2 Determining EC and GL values
4.2.1 Preparing a dilution series
Three or more dilution levels of a sample are needed to determine a GL or EC value
with the luminescent bacteria test. A distinction is made between two types of dilution
series.
Geometrical dilution series
The sample is diluted several times by a factor of 2. The following series of sample
dilutions is obtained:
undiluted sample 1:2 1:4 1:8 1:16 etc. diluted sample
During the luminescent bacteria test a volume of the sample is mixed with the same
volume of the suspension of luminescent bacteria. This further dilution of the above
sample dilutions results in the test dilution series:
1:2 1:4 1:8 1:16 1:32 etc. test dilutions
Dilution series referred to in DIN 38412 L34/341
A dilution series as referred to in DIN 38412 contains a combination of two geometrical
dilution series, one of them based on the undiluted sample and the other on a 1:1.5
dilution of the sample. This gives rise to the following series of sample dilutions:
undiluted sample 1:1.5 1:2 1:3 1:4 etc. diluted sample
During the luminescent bacteria test a volume of the sample is mixed with the same
volume of the suspension of luminescent bacteria. This results in a further dilution of
the above sample dilutions results to give the test dilution series. DIN 38412 refers to
the test dilutions of the sample as G-values:
1:2 1:3 1:4 1:6 1:8 etc. G-values