61-32
FORMALDEHYDE, continued
Iron (Fe
3+
) 12 mg/L
Lead 100 mg/L
Manganese 500 mg/L
Mercury 70 mg/L
Morpholine 0.36 mg/L
Nitrate 1000 mg/L
Nitrite 8 mg/L
Phenol 1050 mg/L
Phosphate 200 mg/L
Silica 40 mg/L
Sulfate 10000 mg/L
Urea 1000 mg/L
Zinc 1000 mg/L
Other aldehydes give a positive interference.
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 concentration solutions,
the standard deviation was ±2.4 µg/L CH
2
O.
Testing zero concentration samples, the limit of detection was 2.9 µg/L
CH
2
O. 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).
SUMMARY OF METHOD
Formaldehyde reacts with MBTH (3-methyl-2-benzothiazoline
hydrazone) and a developing solution to form a blue color in proportion
to the formaldehyde concentration.
REQUIRED REAGENTS
Cat. No.
Formaldehyde Reagent Set (100 Tests) . . . . . . . . . . . . . . . . . . . 22577-00
Includes: (1) 22571-69, (1) 22572-49
Quantity
Description Per Test Unit Cat. No.
Developing Solution For Low
Range Formaldehyde . . . . . 5 mL . . . . . .500 mL . . . . . . . 22572-49
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