Hach DR/850 Procedures Manual page 419

SURFACTANTS, ANIONIC,
Sampling and Storage
Accuracy Check
Method Performance
Interferences
Summary of Method
continued
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
a) Snap the neck off a Detergent Voluette Ampule Standard
Solution, 60 mg/L as LAS (The molecular weight of linear
alkylate sulfonate used to make the standard is 342).
b) Using the TenSette Pipet, add 0.1, 0.2, and 0.3 mL of
standard to three 300-mL samples. Mix thoroughly.
c) Analyze each as described above. The anionic surfactants
reading should increase 0.02 mg/L for each 0.1 mL of
standard added.
d) If these increases do not occur, see Standard Additions
(Section 1) for more information.
Precision
In a single laboratory, using a standard solution of 0.150 mg/L
LAS, two lots of reagent, and the instrument, a single operator
obtained a standard deviation of ±0.010 mg/L LAS as anionic
surfactant.
Estimated Detection Limit
The estimated detection limit for program 26 is 0.020 mg/L LAS.
For more information on the estimated detection limit, see
Section 1.
Perchlorate and periodate ions will interfere. High amounts of
chloride, such as those levels found in brines and seawater, will
cause low results.
Detergents, ABS (alkyl benzene sulfonate) or LAS (linear
alkylate sulfonate) are determined by association with crystal
violet dye and extraction of the ion-pair complex into benzene.
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