418
9.
After the timer
beeps, remove the
stopper and drain the
bottom water layer.
Discard this layer.
Note: Benzene solutions
are a regulated waste and
cannot be poured down the
drain. See Section 3 for
proper disposal of these
materials.
10. Drain the top
benzene layer into a
clean sample cell (the
prepared sample).
Note: The benzene layer
cannot be filtered before
color measurement.
Filtration removes the
blue color.
11. Fill another sample
cell to the 25-mL mark
with pure benzene
(the blank).
12. Place the blank in
the cell holder. Tightly
cover the sample cell
with the instrument cap.
13. Press: ZERO
The cursor will move to
the right, then the
display will show:
0.000 mg/L LAS
14. Place the prepared
sample into the cell
holder. Tightly cover the
sample cell with the
instrument cap.
15. Press: READ
The cursor will move to
the right, then the result
in mg/L anionic
surfactants (LAS) will
be displayed.
Note: Standard Adjust may
be performed using a
prepared standard (see
Standard Adjust in
Section 1).
Note: Acetone may be used
to clean benzene from
glassware.
SURFACTANTS, ANIONIC, continued
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