Hach DR/700 Procedures Manual page 502

NICKEL,
continued
SAMPLING AND STORAGE
Collect samples in acid-washed plastic bottles. Adjust the sample pH to
2 or less with nitric acid (about 5 mL per liter). Preserved samples can
be stored up to six months at room temperature. Before analysis, adjust
the sample pH to between 3 to 8 with 5.0 N Sodium Hydroxide Standard
Solution. Do not exceed pH 8 as this may cause some loss of nickel as a
precipitate. Correct test results for volume additions, see Sampling and
Storage, Volume Additions, (Section I) for more information.
ACCURACY CHECK
Standard Solution Method
Prepare a 0.5 mg/L nickel standard solution by diluting 10.0 mL of a
5-mg/L working stock solution to 100 mL in a 100-mL volumetric flask.
The working stock solution should be prepared daily by diluting
5.00 mL of Nickel Standard Solution, 1000 mg/L as Ni, to 1000 mL
with demineralized water.
Or, using the TenSette Pipet, add 0.2 mL of a Voluette Ampule Standard
Solution for Nickel, 300 mg/L Ni, into a 100-mL volumetric flask.
Dilute to volume with demineralized water. This is a 0.6 mg/L standard
solution.
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 0.600 mg/L Ni
concentration samples, the standard deviation was ±0.0043 mg/L Ni.
Testing zero concentration samples, the limit of detection was
0.0043 mg/L Ni. 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
The following may interfere when present in concentrations exceeding
those listed below:
3+
Al
2+
Ca
2+
Cd
-
Cl
32 mg/L
1000 mg/L as (CaCO
20 mg/L
8000 mg/L
55-54
3
)