Hach DR/700 - Page 567

61-11
COBALT, continued
Fe
3+
10 mg/L
K
+
500 mg/L
Mg
2+
400 mg/L
Mn
2+
25 mg/L
Mo
6+
60 mg/L
Na
+
5000 mg/L
Pb
2+
20 mg/L
Zn
2+
30 mg/L
Highly buffered samples or extreme sample pH may exceed the
buffering capacity of the reagents and require sample pretreatment; see
Interferences, pH (Section I).
SUMMARY OF METHOD
After buffering the sample and masking any Fe
3+
with pyrophosphate,
the cobalt is reacted with 1-(2-Pyridylazo)-2-Naphthol indicator. The
indicator forms complexes with most metals present. After color
development, EDTA is added to destroy all metal-PAN complexes
except nickel and cobalt. This method is unique because nickel and
cobalt can be determined on the same sample.
REQUIRED REAGENTS
Cat. No.
Cobalt Reagent Set (100 Test) . . . . . . . . . . . . . . . . . . . . . . . . . 22426-00
Includes: (4) 7005-66, (4) 21501-66, (2) 21502-32
Quantity
Description Per Test Unit Cat. No.
EDTA Reagent
Powder Pillows . . . . . . . . . 2 pillows . . .50/pkg . . . . . . . . . 7005-66
Phthalate-Phosphate Reagent
Powder Pillows . . . . . . . . . 2 pillows . . .50/pkg . . . . . . . . 21501-66
PAN Indicator
Solution, 0.3% . . . . . . . . . . 2 mL . . . . . .100 mL . . . . . . . 21502-32
Water, demineralized . . . . . . . 25 mL . . . . . 4 L . . . . . . . . . . . . . 272-56
REQUIRED APPARATUS
Clippers, for opening
powder pillows . . . . . . . . . 1 . . . . . . . . .each . . . . . . . . . . . . 968-00
Cylinder, mixing,
graduated, 25 mL . . . . . . . . 2 . . . . . . . . .each . . . . . . . . . . 20886-40