61-31
FORMALDEHYDE, continued
ACCURACY CHECK
Standard Additions Method
a) Snap the neck off a Formaldehyde Voluette Ampule Standard
Solution, 4000 mg/L.
b) Use the TenSette Pipet to add 0.2 mL of standard to a 100-mL
volumetric flask. Dilute to volume with formaldehyde-free water.
Mix well. Prepare daily. This is an 8 mg/L formaldehyde
standard solution.
c) Use the TenSette Pipet to add 0.1 mL, 0.2 mL and 0.3 mL of diluted
standard (8 mg/L) to three 25-mL water samples. Mix each thoroughly.
d) Analyze each sample as described above. The formaldehyde
concentration should increase 32 µg/L for each 0.1 mL of standard added.
e) If these increases do not occur, see Standard Additions (Section I) for
more information.
Standard Solution Method
Prepare a 320 µg/L formaldehyde standard by pipetting 1.0 mL of the
8 mg/L solution from the Accuracy Check into a 50-mL mixing cylinder.
Dilute to 25.0 mL with formaldehyde-free water. Run the test directly
on this sample.
INTERFERENCES
The following may interfere when present in concentrations exceeding
levels listed below.
Acetate 1000 mg/L
Ammonium (as N) 10 mg/L
Aniline 10 mg/L
Bicarbonate 1000 mg/L
Calcium 3500 mg/L
Carbonate 500 mg/L
Chloride 5000 mg/L
Copper 1.6 mg/L
Cyclohexylamine 250 mg/L
Ethanolamine 33 mg/L
Ethylenediamine 1.5 mg/L
Glucose 1000 mg/L
Glycine 1000 mg/L
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