Hach DR2400 - Page 323

Iron
Iron
Iron_PP_Other_FEZ_Eng_Ody.fm Page 3 of 4
Sample Collection, Storage and Preservation
Collect samples in acid-washed glass or plastic bottles. To preserve samples,
adjust the sample pH to 2 or less with concentrated Nitric Acid, ACS
(Cat. No. 152-49) (about 2 mL per liter). Samples preserved in this manner can be
stored up to six months at room temperature. If you are only reporting dissolved
iron, filter the sample immediately after collection and before adding nitric acid.
Before testing, adjust the sample pH to 3–5 with Ammonium Hydroxide, ACS
(Cat. No. 106-49). Do not exceed pH 5, or iron may precipitate. Correct test
results for volume additions; see Section 3.1.3 Correcting for Volume Additions on
page 29.
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. Snap the neck off an Iron Voluette
®
Ampule Standard, 25-mg/L Fe.
5. Prepare a 0.1 mL sample spike by adding 0.1 mL of standard to the unspiked
sample. Touch the timer icon. After the timer beeps, read the result.
6. Prepare a 0.2 mL sample spike by adding 0.1 mL of standard to the 0.1 mL
sample spike. Touch the timer icon. After the timer beeps, read the result.
7. Prepare a 0.3 mL sample spike by adding 0.1 mL of standard to the 0.2 mL
sample spike. Touch the timer icon. After the timer beeps, read the result.
Each addition should reflect approximately 100% recovery. Each 0.1 mL of
standard should cause a 0.1 mL increase in the concentration reading.
8. 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. Using Class A glassware, prepare a 1.0-mg/L Fe standard solution by
pipetting 5.00 mL of Iron Standard Solution, 100-mg/L, into a 500-mL
volumetric flask. Dilute to the mark with deionized water. Prepare this
solution daily. Perform the iron procedure as described above.
2. To adjust the calibration curve using the reading obtained with the 1.0-mg/L
standard solution, touch
Options on the current program menu. Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration. 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.