Hach Eclox, User Manual

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11.6.2 Prepare the test suspension
Prepare enough test suspension (stock suspension and Diluent mixture) to do the
test. Each test tube used for the test is filled with 0.5 mL of test suspension. To
identify the number of test tubes used for a test:
• For D 2 values an higher, add 1 to the number of sample dilution steps to be
measured (e.g. 1 blank + 9 dilutions = 10). Then multiply that number by 2.
• For D 1 values and higher, add 2 to the number of sample dilution steps to be
measured (2 3 dilutions = 5). Then multiply that number by 2.
The Diluent is made according to ISO11348-3 and makes sure that the test is not
negatively affected by the presence of potassium (K+) and magnesia (Mg2+) ions in
the sample. The Diluent is a specially made non-toxic 2% sodium chloride (NaCl)
solution that contains potassium and magnesia ions.
The marine bacterium in the reagent requires the osmotic protection that is given by
the 2% NaCl in the Diluent. The potassium and magnesium in the Diluent stabilize
the light made over time. This stabilization helps keep high negative inhibitions from
getting with samples that contain potassium and magnesium ions.
Do not make Diluent or use substitutes.
11.6.2.1 Test suspension for D 2 values and higher
Prepare the test suspension for D2 values and higher if the sample is expected to be
toxic.
1. Remove the Diluent
from the cool box.
Remove the cap from the
Diluent bottle.
2. Put 50 parts Diluent
solution (D) at refrigerator
temperature into the
reaction vessel using a
pipette.
3. Remove the stock
suspension (rehydrated
reagent) from the cool box.
Remove the rubber
stopper from the reagent
bottle.