Hach Eclox, Руководство пользователя

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11.9 Prepare the sample
To prepare the sample for testing:
1. If the sample is turbid, either:
• Filter the sample with a modified polysulfone filter
Before using other filter materials, test the filter material with 2% NaCl first to
make sure that the filter material can be used with the Luminescent Bacteria
Toxicity Test. Check the acceptable filters in the ISO method.
Note: Do not use a cellulose nitrate or a cellulose acetate filter. The use of cellulose nitrate or
cellulose acetate filters can cause light inhibition that is not caused by the sample.
• Let the sample sediment for 1 hour, or
• Centrifuge the sample (e.g., 10 minutes at 5.000 g)
2. Check the pH level. Adjust the sample to pH 6 to 8 using HCl or NaOH. Use a
strength of HCl or NaOH that does not change the volume of the sample by
more than 5% intotal.
3. Add solid NaCl to the sample until the concentration in the sample is 2% (w/v).
For example, weigh out 0.3 g of NaCl and dissolve it in 15 mL of sample or
dissolve one spoon of solid NaCl (LCX058) in 7 mL of sample. The
concentration of salt in the test should not exceed 35 g/L.
Note: Do not add NaCl to the sample if the salt concentration of the sample is more than 20
g/L (guide value: conductivity of 35 mS/cm).
Note: The salt content of the sample should not exceed 50 g/L. This corresponds to a
conductivity of about 70 mS/cm without taking other conductive compounds into account.
Solid NaCl is used to change the sample osmolarity to a value that is correct for
the marine bacterium used in the test.
4. If the sample has a high toxicity, carry out a preliminary dilution of the sample
with 2% NaCl solution. Select a preliminary dilution from the levels 1:2, 1:4, 1:8,
1:16, etc. to make sure of a continuous dilution series using the dilution
procedure of the manufacturer.