Hach DR2400 - Page 87

Aluminum
Aluminum
Aluminum_UniCell_Other_CHR_Eng_Ody.fm Page 3 of 4
Higher concentrations of heavy metals than those given, as well as fluoride,
phosphate and relatively rare elements such as beryllium, thorium, titanium,
zirconium and vanadium interfere with the determination. Aluminum oxide
hydrates and hydroxide are only partially determined.
Note: Sample pretreatment with the Metal Prep Set (HCT 200) will cause an interference.
Sample Collection, Preservation, and Storage
Collect samples in acid-cleaned glass or plastic containers. No acid addition is
necessary if analyzing the samples immediately. To preserve samples, adjust the
pH to 2 or less with concentrated nitric acid (about 2 mL per liter). Preserved
samples may be stored up to six months at room temperature.
Before analysis, adjust the pH to between 2.0 and 3.5 with 5.0 N Sodium
Hydroxide Standard Solution. Do not exceed pH 3.5 or aluminum may
precipitate or complex. The temperature of the water sample and the sample vial
should be 18–22 °C (64–72 °F).
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
2. Touch
Options. Touch Standard Additions. A summary of the standard
additions procedure will appear.
3. Touch
OK to accept the default values for standard concentration, sample
volume, and spike volumes. Touch
Edit to change these values. After values
are accepted, the unspiked sample reading will appear in the top row. See
Standard Additions in the instrument manual for more information.
4. Measure 250 mL of sample into three graduated cylinders.
5. Pipet 0.1, 0.2, and 0.3 mL of 100-mg/L Al standard solution, respectively, into
the three cylinders and mix thoroughly.
6. Analyze as described in the procedure. Accept each standard additions
reading by touching
Read. Each addition should reflect approximately 100%
recovery.
7. After completing the sequence, touch
Graph to view the best-fit line through
the standard additions data points, accounting for matrix interferences. Touch
View: Fit, then select Ideal Line and touch OK to view the relationship between
the sample spikes and the “Ideal Line” of 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Standard Solution Method
1. Prepare a 0.30-mg/L Al standard solution by pipetting 0.30 mL of 100-mg/
L Al standard into a 100-mL volumetric flask. Dilute to the mark with
deionized water. Stopper and invert to mix. Prepare this solution daily.
Analyze using the procedure described above.
Cr
3+
, Cr
6+
0.5 mg/L
F
–
0.1 mg/L
(continued)
Interfering Substance Interference Levels