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AN-T-109

Iodine value in canola and olive oil

Achieve faster results with the modified standard method

Summary

The iodine number is an important sum parameter for assessing the quality of edible oils
and fats. It provides quantitative information about the presence of unsaturated fats and
oils.  The  higher  the  amount  of  unsaturated  fatty  acids  in  the  sample,  the  more  iodine
reacts with these double bonds, resulting in a higher iodine value. For common oils, such as
sunflower  or  olive  oil,  the  iodine  value  is  well  known.  Hence,  it  can  be  used  as  a  test
parameter for counterfeit detection in the fight against food fraud.

For the classical titrimetric determination, the samples have to be placed in the dark for up
to two hours after the addition of the reaction solution (Wijs solution). In this Application
Note, we describe a modified analysis based on EN ISO 3961, ASTM D5554, AOAC 920.159,
AOAC 993.20, AOCS Cd 1d-92, USP<401> Method II, and Ph.Eur. 2.5.4 Method B. Due to the
modification,  the  reaction  time  reduces  significantly,  from  2  hours  to  5  minutes.  This
modified analysis thus allows for much higher productivity in the lab.

Find more information in the video:

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Configuration

2.1001.0310 - OMNIS Professional Titrator without stirrer 
Innovative, modular potentiometric OMNIS Titrator for endpoint 
titration and equivalence point titration (monotonic/dynamic). 
Thanks to 3S Liquid Adapter technology, handling chemicals is safer 
than ever before. The titrator can be freely configured with 
measuring modules and cylinder units and can have a stirrer added 
as needed. Including "Professional" function license for parallel 
titration with additional titration or dosing modules. Control via PC 
or local network; Connection option for up to four additional 
titration or dosing modules for additional applications or auxiliary 
solutions; Can be supplemented with magnetic stirrer and/or rod 
stirrer; Various cylinder sizes available: 5, 10, 20 or 50 mL; Liquid 
Adapter with 3S technology: Safe handling of chemicals, automatic 
transfer of the original reagent data from the 
manufacturerMeasuring modes and software options:; Endpoint 
titration: "Basic" function license; Endpoint and equivalence point 
titration (monotonic/dynamic): "Advanced" function license; 
Endpoint and equivalence point titration (monotonic/dynamic) with 
parallel titration: "Professional" function license;

2.1010.1010 - OMNIS Sample Robot S Pick&Place 
OMNIS Sample Robot S with a "Peristaltic" (2-channel) pump module 
and a Pick&Place module in addition to extensive accessories for the 
direct transition to fully automatic titration. The system provides 
space in two sample racks for 32 sample beakers of 120 mL each. This 
modular system is supplied completely installed and can thus be put 
into operation in a very short time.The system can also be extended 
upon request to include two additional peristaltic pumps and 
another Pick&Place module, thus doubling the throughput. If 
additional workstations are required, then this Sample Robot is 
already able to be expanded to become an L-sized OMNIS Sample 
Robot, thus enabling samples from seven racks to be processed in 
parallel on up to four Pick&Place modules and quadrupling the 
sample throughput.

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6.00401.300 - dPt Titrode 
Digital, combined platinum ring electrode for OMNIS with a pH glass 
membrane as reference electrode.This maintenance-free electrode is 
suitable for redox titrations when the pH value remains constant, e.
g.: Iodometry; Chromatometry; Cerimetry; Permanganometry; This 
electrode is stored in distilled water.dTrodes can be used on OMNIS 
Titrators. 

Sample and sample preparation

The analysis is demonstrated on canola (rapeseed) oil and olive oil. No sample preparation
is required.

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Experimental

Figure 1. Example of an OMNIS system consisting of an OMNIS Sample Robot S with two 
working stations, an OMNIS Professional Titrator, and a corresponding amount of OMNIS 
Dosing Modules to add all necessary solutions.

The  analysis  is  carried  out  automatically  on  an  OMNIS  system  consisting  of  an  OMNIS
Sample  Robot  S  and  an  OMNIS  Titrator.  The  maintenance-free  dPt  Titrode  is  used  for
indication of the equivalence point.

An appropriate amount of sample is weighed into the titration beaker, then the beaker is
covered with a lid and placed on the sample rack. Before the titration, glacial acetic acid,
Wijs  solution  (ICl),  and  magnesium  acetate  solution  are  added  and  the  solution  is  stirred
for 5 minutes. Afterwards, potassium iodide solution is added and the solution is titrated
with standardized sodium thiosulfate until after the equivalence point.

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Results

Sharp titration curves are obtained where the equivalence point is reliably determined by
the OMNIS software.

Table 1. Mean iodine value for canola (rapeseed) oil and olive oil determined with an 
automated OMNIS system (n = 5).

Canola oil

Olive oil

Iodine value in g I /g

2

109.3

80.9

SD(rel) in %

0.1

0.1

Figure 2. Titration curve of the determination of the iodine value in olive oil with the described OMNIS System.

Conclusion

The  standards  EN  ISO  3961,  ASTM  D5554,  AOAC  920.159,  AOAC  993.20,  AOCS  Cd  1d-92,
USP<401>  Method  II,  and  Ph.Eur.  2.5.4  Method  B  describe  a  procedure  which  needs  a
reaction time of 2 hours. Here, we show a reliable way to determine the iodine value in oils
and  fats  within  just  a  few  minutes.  This  significantly  enhances  sample  throughput  and
reduces the cost per analysis. With an OMNIS system, the analyses can even be carried out
in parallel so that laboratory throughput can be enhanced even further.

Metrohm Česká republika s.r.o.
Na Harfě 935/5c
190 00 Praha

Metrohm Česká republika s.r.o.
[email protected]
tel:+420 246 063 433