Hach DR/850 - Page 409

409
Sampling and Storage
Collect samples in clean plastic or glass bottles. Samples may be
stored up to 28 days by cooling to 4 °C (39 °F) or lower. Warm to
room temperature before analysis.
Accuracy Check
Standard Additions Method- Powder Pillows
a) Snap the neck off a Sulfate Standard PourRite Ampule,
1000 mg/L SO
4
2-
.
b) Use a TenSette Pipet to add 0.1, 0.2 and 0.3 mL of
standard to the three 10-mL samples. Mix thoroughly.
c) Analyze each sample as described above. The sulfate
concentration should increase 10 mg/L for each 0.1 mL of
standard added.
d) If these increases do not occur, see Standard Additions in
Section 1 for more information.
Standard Additions Method- AccuVac Ampuls
a) Snap the neck off a Sulfate Standard PourRite Ampule,
2500 mg/L SO
4
2-
.
b) Fill three 25- mL graduated cylinders with 25 mL of
sample. Use a TenSette Pipet to add 0.1, 0.2 and 0.3 mL of
standard to the three cylinders. Mix thoroughly. For
AccuVac Ampuls, transfer to a
50-mL beaker.
c) Analyze each sample as described above. The sulfate
concentration should increase 10 mg/L for each 0.1 mL of
standard added.
d) If these increases do not occur, see Standard Additions in
Section 1 for more information.
Standard Solution Method
Check the accuracy of the test by using the Sulfate Standard
Solution,
50 mg/L, listed under Optional Reagents. Or, prepare this
solution by pipetting 1.0 mL of a PourRite Ampule Standard for
Sulfate (2500 mg/L) into a 50-mL volumetric flask. Dilute to
volume with deionized water. The final concentration is 50 mg/L
sulfate. Substitute this standard for the sample and proceed with
the test as described in the procedure.
SULFATE, continued