Voltammetric determination of palmitic acid by electrode modified with reduced graphene oxide and gold nanoparticles composite
Palm oil is one of the most produced and traded vegetable oil in the world recently. The quality of palm oil is very important to be examined and one of the quality indices is free fatty acids (FFA) content. Palmitic acid is the major component of monosaturated acids in palm oil and hence is chos...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/92793/1/FS%202021%2015%20-%20IR.pdf |
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| Summary: | Palm oil is one of the most produced and traded vegetable oil in the world
recently. The quality of palm oil is very important to be examined and one of
the quality indices is free fatty acids (FFA) content. Palmitic acid is the major
component of monosaturated acids in palm oil and hence is chosen in
determination of FFA content. Acid-base titration method was traditionally
used to determine acid content, but the presence of high amounts of carotene
causes difficulties to determine the end point of the titration, causing
inaccurate and inconsistent result. Development of alternative methods is
needed to replace traditional method in order to remain competitive in world
of industry. Thus, in this study, an electrochemical technique for the
determination of FFA as alternative to conventional method (titration method)
has been explored. The electrochemical method was developed based on
electrochemically reduced graphene oxide (rGO) and reduced graphene
oxide/gold nanoparticles (rGO/AuNPs) composite deposited onto screenprinted
carbon electrode (SPCE) via drop-casting technique. The modified
electrode was characterized by physico-chemical and electrochemical
methods, respectively. Raman spectroscopy, Field Emission Scanning
Electron Microscope (FESEM), Energy Dispersive X-Ray Spectroscopy
(EDX) and Fourier Transform Infrared Spectroscopy (FTIR) all confirmed the
successful formation of rGO and rGO/AuNPs. Redox signal of the modified
electrode followed the order of rGO/AuNPs > rGO > AuNPs > bare > GO.
The voltammetric behaviour of 2-methyl-1,4-naphthaquinone (VK3) in the
presence of palmitic acid at the modified electrode was investigated in an
acetonitrile/water mixture containing lithium perchlorate (LiClO4). The
determination of palmitic acid was based on the voltammetric reduction of
VK3 to form corresponding hydroquinone which is proportional to the
concentration of palmitic acid. Under optimum condition, the developed
method showed a good linear relationship in the concentration ranging from 0.192 mM to 0.833 mM with the detection limit of 0.065 mM for rGO-modified
SPCE and 0.040 mM for rGO/AuNPs-modified SPCE. For the validation
study using t-test, the calculated t-values for both sensors were found to be
less than the tabulated value which is 3.18, hence the difference between the
two methods used is insignificant at the 95 % confident level and null
hypothesis is accepted. |
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