Hach DR/850, Procedures Manual, Page: 351 / 460

351
Sampling and Storage
Collect sample in plastic or glass bottles that have been cleaned
with 1:1 Hydrochloric Acid Solution and rinsed with deionized
water. Do not use commercial detergents containing phosphate
for cleaning glassware used in this test.
Analyze samples immediately after collection for best results. If
prompt analysis is impossible, preserve samples for up to 48
hours by filtering immediately and storing samples at 4 °C. Warm
to room temperature before testing.
Accuracy Check
Standard Additions Method
a) Fill three 25-mL graduated mixing cylinders with 25 mL of
sample.
b) Snap the neck off a Phosphate PourRite Ampule Standard
Solution, 50 mg/L as PO
4
3-
.
c) Use the TenSette Pipet to add 0.1 mL, 0.2 mL, and 0.3 mL
of standard, respectively, to the three mixing cylinders.
Stopper each and mix thoroughly.
d) For analysis with AccuVacs, transfer solutions to dry,
clean 50 mL beakers to fill the AccuVac ampules. For
analysis with powder pillows, transfer only 10 mL of
solution to the sample cells.
e) Analyze each standard addition sample as described in the
procedure. The phosphate concentration should increase
0.2 mg/L PO
4
3-
for each 0.1 mL of standard added.
f) If these increases do not occur, see Standard Additions in
Section 1 .
Standard Solution Method
Prepare a 2.0 mg/L PO
4
3-
standard solution by pipetting 4.0 mL
of Phosphate Standard Solution, 50 mg/L as PO
4
3-
, into an acid-
washed Class A 100-mL volumetric flask. Dilute to volume with
deionized water. Stopper and invert to mix. Use this solution in
place of the sample in the procedure to insure the accuracy of the
test. The mg/L PO
4
3-
reading should be 2.00 mg/L.
PHOSPHORUS, REACTIVE,
continue