Hach DR2400 - Page 797

Zinc
Zinc
Zinc_UniCell_Other_PAR_Eng_Ody.fm Page 3 of 4
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. If reporting only
dissolved free zinc, filter sample immediately after collection and before adding
nitric acid.
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. Prepare three sample spikes by filling three mixing cylinders with 100 mL of
sample. Pipet 0.1, mL, 0.2 mL, and 0.3 mL of 1000-mg/L Zn standard,
respectively, to each sample and mix thoroughly.
5. Transfer 4 mL of each solution into a sample vial and analyze as described in
the procedure. Touch
Read to accept each standard additions reading. Each
addition should reflect approximately 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Standard Solution Method
1. Prepare a 2.00-mg/L Zn Standard Solution by pipetting 0.2 mL of Zinc
Standard Solution, 1000-mg/L, into a 100-mL volumetric flask. Dilute to the
mark with deionized water. Stopper and invert to mix. Prepare this solution
daily. Perform the zinc procedure as described above.
2. To adjust the calibration curve using the reading obtained with the
2.00-mg/L standard solution, touch
Options on the current program menu.
Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration (the value
depends on the selected chemical form). If an alternate concentration is used,
touch the number in the box to enter the actual concentration, then touch
OK.
Touch
Adjust.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.