Hach DR/700 Procedures Manual page 481

DEHA,
continued
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 reagent. Testing 200 µg/L DEHA concentration
solutions, the standard deviation was ±2.4 µg/L DEHA.
Testing zero concentration samples, the limit of detection was 3.1 µg/L
DEHA. The limit of detection was calculated as three times the standard
deviation when testing zero concentration samples (adapted from
Analytical Chemistry, 1980, 52, 2242-2249).
INTERFERENCES
Substances which reduce ferric iron (such as other oxygen scavengers)
will interfere. Substances which complex iron strongly may also
interfere. The following may interfere when present in concentrations
exceeding those listed below:
Borate (as Na B O
2 4
Cobalt
Hardness (as CaCO
Lignosulfonates
Molybdenum
Phosphate
Phosphonates
Sulfate
Zinc
Light interferes with the color development.
SUMMARY OF METHOD
Diethylhydroxylamine (DEHA) or other oxygen scavengers present in
the sample react with ferric iron in DEHA Reagent 2 Solution to
produce ferrous ion in an amount equivalent to the DEHA concentration.
This solution then reacts with DEHA 1 Reagent, which forms a purple
color with ferrous iron.
Using this procedure other oxygen scavengers can be determined by
multiplying the DEHA results by the appropriate multiplier.
)
7
)
3
55-33
500 mg/L
0.025 mg/L
1000 mg/L
0.05 mg/L
80 mg/L
10 mg/L
10 mg/L
1000 mg/L
50 mg/L