Hach DR/700 - Page 262

50-12
IRON, FERROUS, continued
ACCURACY CHECK
Standard Solution Method
Prepare a ferrous iron stock solution (100 mg/L Fe
2+
) by dissolving
0.7022 grams of Ferrous Ammonium Sulfate, hexahydrate, in
demineralized water. Dilute to 1 liter. Prepare immediately before use.
Dilute 1.0 mL of this solution to 100 mL with demineralized water to
make a 1.0 mg/L standard solution. Prepare this immediately before use.
STATISTICAL EVALUATION
A single operator repetitively tested samples of two laboratory prepared
solutions, using one DR/700, matched sample cells and two
representative lots of testing reagents. Testing 1.50 mg/L Fe
2+
concentration samples, the standard deviation was ±0.008 mg/L Fe
2+
.
Testing zero concentration samples, the limit of detection was 0.007 mg/L
Fe
2+
. The limit of detection was calculated as three times the standard
deviation whin testing zero concentration samples (Adapted from
Analytical Chemistry, 1980, 52, 2242-2249).
Using two representative lots of Ferrous Iron AccuVac Ampuls, the
standard deviation was 0.014 mg/L Fe
2+
.
SUMMARY OF METHOD
The 1,10 phenanthroline indicator in Ferrous Iron Reagent reacts with
ferrous iron in the sample to form an orange color in proportion to the
iron concentration. Ferric iron does not interfere. The ferric iron (Fe
3+
)
concentration can be determined by subtracting the ferrous iron
concentration from the results of a total iron test.
REQUIRED REAGENTS (Using Powder Pillows)
Quantity
Description per test Unit Cat. No.
Ferrous Iron Reagent
Powder Pillows, 25-mL . . . 1 pillow . . . .100/pkg . . . . . . . . 1037-69
REQUIRED APPARATUS (Using Powder Pillows)
Clippers, large,
for opening pillows. . . . . . . 1 . . . . . . . . .each . . . . . . . . . . . . 968-00
DR/700 Filter Module
Number 50.01. . . . . . . . . . . 1 . . . . . . . . . each . . . . . . . . . . 46250-00