Hach DR/700 Procedures Manual page 369

CADMIUM,
h) For Standard 1, use the blank from the cadmium procedure and make
the display show 0000 µg/L.
i) For Standard 2, use the prepared sample from the cadmium procedure
and make the display show 0080 µg/L.
INTERFERENCES
The following do not interfere:
Aluminum
Antimony
Arsenic
Calcium
Chromium
Cobalt
Iron
The following interfere causing high results when present in
concentrations exceeding those listed below:
Copper
Bismuth
Mercury
Silver
Eliminate interference from these metals by the following treatment,
beginning after Step 6.
a) Measure about 5 mL of the DithiVer solution into the separatory
funnel. Stopper the funnel, invert and open the stopcock to vent. Close
the stopcock and shake the solution vigorously for 15 seconds. Allow
the funnel to stand undisturbed until the layers separate (about 30
seconds). A yellow, red, or bronze color in the bottom (chloroform)
layer confirms the presence of interfering metals. Draw off and discard
the bottom (chloroform) layer.
b) Repeat extraction with fresh 5 mL portions of the DithiVer solution
(discarding the bottom layer each time) until the bottom layer shows a
pure dark green color for three successive extracts. Extractions can be
repeated several times without appreciably affecting the amount of
cadmium in the sample.
continued
52-43
Lead
Magnesium
Manganese
Nickel
Tin
Zinc
2 mg/L
80 mg/L
all levels
2 mg/L