57-43
SILVER, 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 testing reagents. Testing 0.500 mg/L Ag
concentration samples the standard deviation was ±0.0036 mg/L Ag.
Testing zero concentration samples, the limit of detection was
0.0049 mg/L Ag. 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
Interfering studies were conducted by preparing a known silver solution
(about 0.4 mg/L) and the potential interfering ion. The ion was said to
interfere when the resulting concentration changed by ±10%.
Negative Interference: Interference Level
Aluminum 30 mg/L
Ammonia 750 mg/L
Cadmium 15 mg/L
Chloride 19 mg/L
Chromium, hexavalent 90 mg/L
Copper 7 mg/L
Iron 30 mg/L
Lead 13 mg/L
Manganese 19 mg/L
Nickel 19 mg/L
Zinc 70 mg/L
Positive Interference:
Calcium 600 mg/L
Magnesium 2000 mg/L
Mercury 2 mg/L
DIGESTION
The following digestion steps are for samples containing organic matter,
thiosulfate or cyanide from wastewater, silver electroplating baths and
silver strike solutions. Digestion must be carried out in a Digesdahl
Digestion Apparatus.
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