Hach HCT 159 User Manual

Iron (0.10 - 5.00 mg/L Fe)

UniCell™ Test

Scope and Application: For drinking water, raw water, swimming-bath water, waste water and process control

HCPE 159 B / Druckfarbe schwarz / 1

SUMMARY OF METHOD

Iron(II) ions form an orange-red complex with 1.10-phenanthroline.
Any iron(III) ions present in the water sample are reduced to iron(II)
ions by ascorbic acid before the complex is formed. This method
complies with regulations in many countries and therefore can often
be used for reporting purposes. Contact your local Hach distributor
to determine if this method can be used for regulatory reporting
purposes in your country.

SHELF LIFE OF TEST REAGENT

The test reagents are stable at room temperature for 30 months as
indicated by the expiration date on the package.

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 2.00 ml per liter). Preserved samples may be stored up
to six months at room temperature. If reporting only dissolved free
iron, filter sample immediately after collection and before adding
nitric acid.

Before analysis, adjust the pH to between 3 and 5 with

5.0 N sodium hydroxide standard solution. Do not exceed pH 5
as iron may precipitate. Correct the test results for volume additions.

INTERFERENCES

The ions listed in the table have been individually checked up to the
given concentrations. Cumulative effects and the influence of other
ions have not been evaluated. There is no interference from:

1000 mg/L: Cl

-

500 mg/L: Ca

2+

100 mg/L: Ag

+

70 mg/L: Cd

2+

50 mg/L: Co2+, Zn2+, Pb2+, CO

3

2-

, Hg2+, Cr3+, Cr

6+

25 mg/L: Ni

2+

10 mg/L: Cu

2+

5 mg/L: Sn

2+

Higher amounts of copper, nickel, and tin cause high-bias results.

Total iron including undissolved iron and complexed iron can only
be determined after digesting with the Metal Prep Set HCT 200.
(Total iron measuring range 0.12 – 6.00 mg/L).

ACCURACY CHECK
Standard Solution Method

Prepare a 3.00 mg/L Fe standard solution by pipetting 0.30 ml of
1000 mg/L Fe into a 100 ml volumetric flask. Dilute to the
mark with deionized water. Stopper and invert to mix. Prepare this
solution daily. Perform the iron procedure as described.

Standard Addition Method

(a) Measure 100 ml of sample into three mixing cylinders.
(b) Using a pipette add 0.10, 0.20 and 0.30 ml of 1000 mg/L Fe

standard solution to the three samples. Mix well.

(c)

Analyze each sample using the procedure.
The Fe concentration should increase 1.00 mg/L for each

0.10 ml of standard added.

METHOD PERFORMANCE
Precision

In a single laboratory, using a standard solution of 3.00 mg/L Fe and
two representative lots of reagent, a single operator obtained
a standard deviation of +/- 0.15 mg/L on a total of 14 samples.

TIPS AND TECHNIQUES

1. Adjust pH of preserved samples to between pH 3 – 5

before analysis. Water samples with pH < 2 affects the reagent.

2. The outside of the vial must be clean before placing it in the
instrument. Wipe it down with a damp towel, followed by a dry
one.

3. For a proof of accuracy, use the standard solution or standard
addition method. (See Accuracy Check).

4. See your Instrument’s Procedure Manual for instructions on
adjusting the calibration curve if needed.

5.The temperature of the water sample and the sample vial
should be between 15 – 25°C (59 – 77F).

SAFETY

Good safety habits and laboratory techniques should be used
throughout the procedure. Consult the Material Safety Data Sheet
for information specific to the reagents used.

HCT 159

US/GB

5

1

3

4.0ml

Sample

2

4

15 min

PROCEDURE for Free Iron

applies to DR/4000, DR/2500 DR/2010 and DR/800

Note

If this is the first time you have run this revision of the test on
your DR/4000, you must contact your local Hach distributor
for an upgrade of your software (Cat.No. 49544-00). Software
Version number 2.39 contains the factory UniCell™ programs.

INSTRUMENT SET-UP

1. Press the soft key under HACH PROGRAM (or
USER PROGRAM if the method was entered as a
USER PROGRAM).

Enter program number 2130 (or 159 if the method was
entered as a USER PROGRAM).
Press ENTER.

2. The display will show:

HACH PROGRAM: 2130
Iron, HCT 159

The wavelength (

λ), 485 nm, is automatically selected.

3. Insert the Test N’Tube adapter into the cell holder by
sliding it under the thumb screw and into the alignment
grooves. Fasten in place by tightening the thumb screw.

4. Follow the procedure steps.

(Note: If measuring Total Iron and performed the sample
digestion using the HCT 200 Metal Prep Set, select the
Total Iron alternate form under the Options soft key menu).

5. Wipe the outside of the zero vial.
Place the zero vial into the adapter.
Close the light shield.

6. Press the soft key under ZERO.
The display will show: 0.00 mg/L Free-Fe or

0.00 mg/L Tot-Fe if the Total Iron alternate form
was selected.

7. Clean the outside of the sample vial.

8. Place the prepared sample vial into the adapter. Close
the light shield. Results in mg/L Free-Fe or To t- Fe are
displayed.

Note

If the test overranges, repeat the UniCell™ test with diluted
sample.

2.Pipet 4.0 ml sample
into the sample vial.

3. Close sample vial and
invert a few times, until
the freeze-dried
contents are
completely dissolved.

4. Start the instrument
timer.
A 15-minute reaction
period will beginn.

5. Zero the instrument
using the zero vial
(white cap) provided
and read the sample.

DR / 4000—Rev 2.39

1. Enter program number
and set up the
instrument as explained
for each instrument
type.

HCT 159 HCT 159

LIST OF REQUIRED REAGENTS

Iron-Fe
UniCell™ HCT 159 23/pkg HCT 159

OPTIONAL REAGENTS

Metal Prep Set
UniCell™ HCT 200 50 digestions HCT 200

Iron Standard
1000 mg/L as Fe 100 ml 2271-42

Sodium Hydroxide
Standard Solution 1000 ml 2450-53
(5.0 N)

Nitric Acid, concentrated 500 ml 152-49

OPTIONAL APPARATUS

Cylinder, mixing – 100 ml each 20886-42
Flask, volumetric 100 ml each 547-42
Pipettor, (Jencons) 1-5 ml each 27951-00
Replacement tips for 27951-00 pk/100 27952-00
Pipettor, (Jencons) 100-1000 µl each 27949-00
Replacement tips for 27949-00 pk/400 27950-00
pH Paper pk/100 26013-00

MEASURING RANGE:

0.10 - 5.00 mg/L Free-Fe / 0.12 - 6.00 mg/L Tot-Fe

PROCEDURE

for Total Iron:

After digestion with the Metal Prep Set HCT 200,
follow the procedure steps 1 – 5.

ZERO