Hanna Instruments HI 903 - Manual (Page 183)

Method ID: HI8107EN
Moisture Determination in Margarine
by external dissolution
Titrator Application Methods: General Methods - r. 0.4
Description:
Method for the determination of moisture in
Margarine by external dissolution. The results are
expressed in % mass and should be between 15
and 30 %.
Electrode:

HI 76320 Double Platinum Pin Electrode
Reagents:

5 mg/mL One-Component KF Volumetric Titrant

Solvent for KF Volumetric Titration

Dry Methanol

Dry Chloroform
Other Accessories:

A clean, dry 1-mL syringe

A clean, dry 22-gauge , 6” non-coring septum
penetration needle

GL 45-Thread Solvent Bottle

100-mL dissolution bottle with septum

Magnetic stirrer and stirbar
External Dissolution Procedure:

To an external dissolution bottle with septum, add
a magnetic stir bar. Weigh the bottle and record
this value.

Add 20 g of dry methanol and 20 g of dry
chloroform to the bottle and stir for 15 to 20
minutes.

Determine the moisture content of the solvent mix.
For the determination of the exact concentration of
the solvent mix, follow HI8301EN Solvent w/
5mg/mL 1-comp.

Enter the solvent moisture concentration by
pressing Method Options, then Sample
Parameters, then External Solvent Concentration.
Use the numeric keypad to enter the exact
concentration. Press Accept or Enter.

Weigh the dissolution bottle to determine the
weight of the remaining solvent (by subtracting the
empty bottle mass). Enter the exact mass by re-
entering Sample Parameters and selecting
External Solvent Size. Use the numeric keypad to
enter the exact mass. Press Accept or Enter.

Add 2.0 to 4.0 g of margarine to the bottle. Weigh
the bottle to determine the exact dissoluted
sample weight. Enter the exact mass by re-
entering Sample Parameters and selecting
Dissoluted Sample Size. Use the numeric keypad
to enter the exact mass. Press Accept or Enter.

To dissolve the margarine, mix for 20 to 30
minutes. The resulting solution will be used to
determine the water content.
Note: Titrate the solution immediately.
Titration Procedure:

Setup titrator according to the instruction manual.
 Press “Select Method” from the main screen. Use
the
arrow keys to highlight ‘HI8107EN Moisture in
Margarine ’ and press “Select”.

Install a 5-mL burette filled with 5 mg/mL One-
Component KF Volumetric Titrant and verify that
no air bubbles are present in the burette or tubing.
If necessary prime until all air has been removed
completely.
For the determination of the exact concentration of
the titrant follow HI8001EN 5.0 mg/mL Titrant
Standardization using Liquid Water Standard.

Connect the solvent bottle top assembly to the
bottle of methanol according to the manual.

Prepare the titration vessel according to the
manual. Dispense enough solvent from the solvent
bottle to fill the vessel to the “min” line (about 50
mL).
 Press “Start/Stop” to pre-titrate the titration solvent
and the titration vessel moisture. Allow the
background
drift rate to stabilize before
proceeding to the next step.

Fill the syringe and needle with the sample
solution.

Weigh the syringe, needle and sample solution.
 Press “Start Analysis”. You will be prompted to
enter the sample size.

Dispense 0.5000 g to 1.0000 g of sample solution
into the titration vessel through the septum using
the needle. Pay attention not to get any sample
on the electrode or beaker walls. If necessary
swirl the titration vessel by hand.

Clear the needle of residual sample by intaking a
small volume of air from the titration vessel. If a
“hanging drop” of sample is seen on the end of the
needle, dip the end of the needle briefly in the
solvent.

Remove the needle from the titration vessel and
weigh the syringe again in order to determine the
added sample mass (by difference of the two
measurements.)

Use the numeric keypad to enter the exact weight
and press “Enter” to start the analysis.
 At the end of the titration the “Sample Analysis
Result
” screen is displayed. The results are
expressed in % mass of water.

The use of external dissolution increases the
precision and drastically lowers the load of the
solvent, allowing you to run more titrations without
changing the solvent. Use fresh solvent after
every 12 - 16 titrations.