Hach DR2400 - Page 346

Iron, Total
Iron, Total
Page 4 of 6
IronTot_AVPP_Other_TPT_Eng_Ody.fm
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 about 2 mL/L Nitric Acid, ACS
(Cat. No. 152-49). Store preserved samples up to six months at room
temperature. If reporting only dissolved iron, filter sample immediately
after collection and before adding nitric acid.
Before testing, adjust the pH of the stored sample to between 3–4 with 5.0 N
Sodium Hydroxide Standard Solution (Cat. No. 2450-26). Do not exceed pH 5 as
iron may precipitate. Correct the test result 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, 10-mg/L Fe.
5. Prepare three sample spikes. Fill three mixing cylinders (Cat. No. 1896-40)
with 10 mL of sample. Use the TenSette
®
Pipet to add 0.2 mL, 0.4 mL, and
0.6 mL of standard, respectively, to each sample and mix thoroughly.
Note: For AccuVac
®
Ampuls, fill three mixing cylinders (Cat. No. 1896-41) each with 50-mL of
sample and spike with 0.4 mL, 0.8 mL, and 1.2 mL of standard. Transfer 40 mL from each of
the three mixing cylinders to three 50-mL beakers (Cat. No. 500-41H). Analyze each
standard addition sample as described in the procedure above. Accept each standard
additions reading by touching Read. Each addition should reflect approximately 100%
recovery.
6. Analyze each sample spike as described in the procedure above, starting with
the 0.1 mL sample spike. 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. Using Class A glassware, prepare a 1.000-mg/L iron 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
1.000 mg/L standard solution, touch
Options on the current program menu.
Touch
Standard Adjust.