Hach DR/850, Procedures Manual, Page: 220 / 460

220
Sampling and Storage
Collect samples in glass or plastic bottles.
Accuracy Check
Standard Addition Method
a) Add 25 mL of sample to three 25-mL mixing cylinders.
b) Snap the neck off a Molybdenum PourRite Ampule
Standard Solution, 75 mg/L Mo
6+
.
c) Use the TenSette Pipet to add 0.1, 0.2 and 0.3 mL of standard,
respectively, to three 25-mL samples. Mix thoroughly.
d) Analyze 20 mL of each spiked sample as described in the
procedure. The molybdenum concentration reading
should increase by 0.3 mg/L for each 0.1 mL addition of
standard.
e) If these increases do not occur, see Standard Additions in
Section 1 for more information.
Standard Solution Method
Prepare a 2.0-mg/L molybdenum standard solution by pipetting
10 mL of a 10-mg/L Molybdenum Standard Solution into a 50-
9.
Insert the blank into
the cell holder. Tightly
cover the sample cell
with the instrument cap.
10.
Press:
ZERO
The cursor will move to
the right, then the
display will show:
0.00 mg/L Mo6
Note: If Reagent Blank
Correction is on, the
display may flash “limit”
(see Section 1).
11.
Place the developed
sample into the cell
holder. Tightly cover the
sample cell with the
instrument cap.
12.
Press:
READ
The cursor will move to
the right, then the result
in mg/L molybdate
molybdenum will
be displayed.
Note: Standard Adjust may
be performed using a
prepared standard
(see Section 1).
MOLYBDENUM, MOLYBDATE, LR,
continued