Hach DR2400 - Page 299

Hardness
Hardness
Hardness_None_Other_CLC_Eng_Ody.fm Page 3 of 4
Interferences
Sample Collection, Storage and Preservation
Collect samples in acid-washed plastic bottles. Adjust the sample pH to 2 or less
with Nitric Acid (about 5 mL per liter) (Cat. No. 152-49). Cool samples to 4 °C.
Preserved samples can be stored up to six months. Before analysis, adjust the
sample pH to between 3 and 8 with 5.0 N Sodium Hydroxide Standard Solution
(Cat. No. 2450-32). Correct the test results for volume additions; see Section 3.1.3
Correcting for Volume Additions on page 29.
Method Performance
Precision
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Interfering Substance Interference Levels and Treatments
Chromium (
3+
) Above 0.25 mg/L
Copper (
2+
) Above 0.75 mg/L
EDTA, chelated Above 0.2 mg/L as CaCO
3
EDTA or EGTA
Traces remaining in sample cells from previous tests will give erroneous results. Rinse cells
thoroughly before using.
Iron (
2+
) Above 1.4 mg/L
Iron (
3+
) Above 2.0 mg/L
Manganese (
2+
) Above 0.20 mg/L
Zinc (
2+
) Above 0.050 mg/L
Ca >1.0 mg/L;
Mg >0.25 mg/L
For the most accurate calcium test result, rerun the test on a diluted sample if the calcium is over
1.0 and the magnesium is over 0.25 mg/L as CaCO
3
. No retesting is needed if either is below
those respective concentrations.
Program Standard as CaCO
3
95% Confidence Limits of Distribution
as CaCO
3
220 2.50 mg/L Ca 2.36–2.64 mg/L Ca
225 2.16 mg/L Mg 2.08–2.24 mg/L Mg
Program Portion of Curve ∆Abs
∆Concentration
as CaCO
3
220 Entire range 0.010 0.05 mg/L Ca
225 Entire range 0.010 0.02 mg/L Mg