Analytical Method: Δ-K232 nm value of olive oil according to Commission Regulation (EEC) No 2568/91 Annex IX

Materials and reagents:
Cat. No. 104718  Isooctane for spectroscopy Uvasol® or
Cat. No. 102822  Cyclohexane for spectroscopy Uvasol®
Cat. No. 100784  Rectangular cells quartz 10 mm
Cat. No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or
Cat. No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600
Volumetric flasks, class A, volume range 25 ml to 100 ml
Analytical balance 0.001 g
Paper filters

Method and measuring range:
Method No. 2525
0 – 4.00 K232

Sample preparation:
Homogenize liquid samples at 30 °C.
Heat solid samples to a temperature of max. 10 °C above the melting point, melt, and homogenize.
If conterminations are present, filter the sample over a fast filtering paper.

Weigh the sample into a volumetric flask, accurately weighed to 1 mg. The quantity of the sample and volume of the volumetric flask must be selected in such a way that the measurement solution exhibits an absorbance between 0.1 and 0.8 A at 232 nm. The following table can be used for orientation:

 

K232 value Weight Volumetric
flask
<0.10 1.00 g 25 ml
0.10 - 0.80 0.25 g 25 ml
0.80 - 1.60 0.25 g 50 ml
1.60 - 4.00 0.20 g 100 ml

 

Add a few millilitres of isooctane or cyclohexane and dissolve the sample at room temperature. Subsequently make up the contents of the volumetric flask to the mark with the selected solvent and mix.
Filter turbid solutions over a paper filter.

Zero adjustment:
For each measurement series, a zero adjustment is required.
It is recommended to use the same cell for zero adjustment and for sample measurement.
The zeroing procedure for the measurement series is automatically prompted by the instrument.

For zero adjustment fill 10-mm rectangular quartz cell with the selected solvent.
After prompting, place the rectangular cell filled with solvent in the cell compartment, the zero adjustment is executed automatically.
Confirm the implementation of zero adjustment with "OK".
The zero adjustment is valid for the entire measurement series.

Measurement procedure:
Select method 2525 "K232 (olive oil)" from method list.

Enter the weight in gram, and confirm with "OK".
To enter the volume of the sample solution, tap the input field in the “Sample Solution” line, enter the volume in milliliters, and confirm with "OK".
Press "START" to reach the measuring mode.

Prior to the measurement of the first sample the system automatically prompts a zero adjustment (procedure see "Zero adjustment").

Transfer the sample solution into a 10-mm rectangular quartz cell and place the rectangular cell into the cell compartment, the measurement is performed automatically.
Confirm measurement with "OK".
The K232 value is shown in the display.

Press "START" to start the measurement procedure for the next sample. The system does not prompt a repeat of the zero adjustment.


Note:

This method is also suited for other oils and fats and in addition to Commission Regulation No 2568/91 Annex IX is based on:

DGF Standard Methods C-IV 6 (13)

ISO 3656:2011

COI/T.20/Doc. No. 19/Rev. 3 (2015)

CODEX STAN 33-1981 (2013)

AOCS Ch 5-91(2009)


 

Low K values are characteristic for high-quality, extra native olive oils; refined or aged olive oils exhibit higher K values at the 232, 268, and 270 nm wavelengths.

 

The limits for olive oils can be referenced from Commission Regulation No. 2568/91 Annex IX.

 

 

Materials

     
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