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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
