45-36
PHENOLS, continued
three separate 500-mL volumetric flasks. Dilute each to the mark with
demineralized water.
d) Perform the procedure with each of the three standard solutions and
verify that the test results are correct.
STATISTICAL EVALUATION
A single operator repetitively tested samples of two laboratory prepared
solutions, using one DR/700, matched sample cells and two
representative lots of reagent. Testing 0.100 mg/L phenols
concentration solutions, the standard deviation was ±0.0047 mg/L
phenols.
Testing zero concentration samples, the limit of detection was 0.006 mg/L
phenols. The limit of detection was calculated as three times the standard
deviation when testing zero concentration samples (adapted from
Analytical Chemistry, 1980, 52, 2242-2249).
INTERFERENCES
The sample pH must be between 3 and 11.5 for the best results. In the
presence of sulfides or suspended matter, the following pretreatment will
be necessary:
a) Take a water sample by filling a clean 500-mL graduated cylinder to
the 350-mL mark. Pour the sample into a clean 500-mL erlenmeyer
flask.
b) Add the contents of one Sulfide Inhibitor Reagent Powder Pillow.
Swirl to mix.
c) Filter 300 mL of the sample through a folded filter paper. Use this
solution in Step 4.
Interference can be caused by reducing agents and oxidizing agents such
as chlorine.
Sample distillation as described in the following steps will eliminate
interferences.
a) Set up the distillation apparatus for the test by assembling the general
purpose apparatus as shown in the Hach Distillation Apparatus Manual.
Use the 500-mL erlenmeyer flask to collect the distillate. It may be
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