Hach DR2400 Manual page 757

Interferences
Sample Collection, Storage, and Preservation
Accuracy Check
Detergents_None_Other_CVI_Eng_Ody.fm
Interfering Substance
Chloride
Perchlorate ions
Periodate ions
Collect samples in clean plastic or glass bottles. Analyze samples as soon as
possible, but they may be stored at least 24 hours by cooling to 4 °C (39 °F).
Warm to room temperature before testing.
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument. Verify that the units displayed are in mg/L.
2. Touch . Touch
Options
additions procedure will appear.
3. Touch to accept the default values for standard concentration, sample
OK
volume, and spike volumes. Touch
are accepted, the unspiked sample reading will appear in the top row. See
Standard Additions in the instrument manual for more information.
4. Snap the neck off a Detergent Voluette
5. Prepare three sample spikes. Fill three beakers with 300 mL of sample. Use
®
the TenSette Pipet to add 0.1 mL, 0.2 mL, and 0.3 mL of standard,
respectively, to each sample and mix thoroughly.
6. Analyze each sample spike as described in the procedure above, starting with
the 0.1 mL sample spike. Accept each standard additions reading by touching
. Each addition should reflect approximately 100% recovery.
Read
Note: The anionic surfactant reading should increase 0.02 mg/L for every 0.1 mL of
standard added.
7. After completing the sequence, touch
the standard additions data points, accounting for matrix interferences. Touch
, then select
View: Fit
the sample spikes and the "Ideal Line" of 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Surfactants, Anionic (Detergents)
Interference Levels and Treatments
High amounts of chloride, such as those levels found in brines
and seawater, will cause low results.
Interferes at all levels.
Interferes at all levels.
. A summary of the standard
Standard Additions
to change these values. After values
Edit
®
Ampule Standard, 60-mg/L LAS.
Graph
and touch
Ideal Line OK
to view the best-fit line through
to view the relationship between
Surfactants, Anionic (Detergents)
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