Hach DR/850 Procedures Manual page 388

PHOSPHORUS, REACTIVE,
5.
Add 1 mL of Amino
Acid Reagent Solution.
Cap and invert several
times to mix (the
prepared sample).
Note: A blue color will
form if phosphate is present.
Note: You may substitute
the contents of one Amino
Acid Reagent Powder
Pillow for 1 mL of Amino
Acid Reagent Solution.
9.
Press:
ZERO
The cursor will move to
the right, then the
display will show:
0.0 mg/L PO4
Note: If Reagent Blank
Correction is on, the
display may flash "limit".
See Section 1.
Sampling and Storage
continued
6.
Press:
TIMER ENTER
A 10-minute reaction
period will begin.
Note: Perform Step 7 while
the timer is running.
10.
Place the prepared
sample into the cell
holder. Tightly cover the
sample cell with the
instrument cap.
Collect samples in clean plastic or glass bottles that have been
cleaned with 1:1 Hydrochloric Acid Solution and rinsed with
deionized water. Do not use a commercial detergent containing
phosphate for cleaning glassware used in this test.
7.
Pour 25 mL of
sample (the blank) into a
sample cell.
11.
Press:
READ
The cursor will move to
the right, then the result
in mg/L PO will
4
be displayed.
Note: Standard Adjust may
be performed using a
prepared standard (see
Section 1).
388
8.
When the timer
beeps, the display
will show:
mg/L PO4
Place the blank into the
cell holder. Cover the
sample cell with the
instrument cap.