Hach DR/850, Procedures Manual, Page: 246 / 460

246
Accuracy Check
Standard additions Method
a) Fill three 25-mL graduated mixing cylinders with 15 mL
of sample.
b) Snap the neck off a Nitrate Nitrogen Ampule Standard
Solution, 12.0 mg/L NO
3
-
-N.
c) Using the TenSette Pipet, add 0.1, 0.2, and 0.3 mL of the
standard to the three samples. Stopper and mix well.
d) Analyze each sample as described above. The nitrate
nitrogen concentration should increase 0.08 mg/L for each
0.1 mL of standard added.
e) If these increases do not occur, see Standard Additions
(Section 1) for more information.
Standard Solution Method
Prepare a 0.20 mg/L nitrate nitrogen standard by diluting 2.00 mL
of a
10.0 mg/L Nitrate Nitrogen Standard Solution to 100.0 mL with
deionized water. Use this standard in place of sample in Step 3.
Standard Adjust
To adjust the calibration curve using the reading obtained with
the 0.20-mg/L standard solution, press the
SETUP
key and scroll
(using the arrow keys) to the STD setup option. Press
ENTER
to
activate the standard adjust option. Then enter
0.20
to edit the
standard concentration to match that of the standard used. Press
ENTER
to complete the curve adjustment. If you are using a
reagent blank correction, the blank correction should be entered
before the Standard Adjust feature is entered. See
Section 1 ,
Standard Curve Adjustmen t for more information.
Method Performance
Precision
In a single laboratory using a standard solution of 0.25 mg/L
nitrate nitrogen (NO
3
-
-N) and two representative lots of reagent
with the instrument, a single operator obtained a standard
deviation of +0.03 mg/L nitrate nitrogen.
NITRATE, Low Range,
continued