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Mikrobølgeassistert derivatisering av triglyserider og frie fettsyrer, samt stabilitetsstudier av hydroksyfettsyremetylestere

Koht, Emilie; Nome, Silje
Master thesis
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http://hdl.handle.net/11250/186363
Issue date
2011-08-25
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  • Master's theses (KBM) [557]
Abstract
A method for acid catalysed microwave transesterification of triglycerides was developed

with BF3 as catalyst. GC-MS was used for quantitative and qualitative analysis of fatty acid

methyl esters (FAMEs) obtained after transesterification. The yield in per cent of FAMEs was

calculated from their corresponding chromatogram areas against the area of an internal

standard.

It was noticed that the optimal power and reaction time was 70 W and 7 minutes with RSD <

10% for each FAME. This indicates good reproducibility and precision. The yield varied

according to FAME, so that the average yield (%) of the employed FAMEs (C16:1, C18:1,

C18:2, C20:1, C20:4, C20:5, C22:1 and C22:6) was 80% ± 12 with RSD equal 16%.

It was investigated if the acid catalyst HCl and the base catalyst CH3ONa could be more

suitable at microwave assisted transesterification than BF3 in respect of reaction time and

yield of FAMEs. HCl obtained a lower average yield at all the points of time and with almost

twice as high a value of RSD (30%). This means that BF3 obtained better precision of the

results and was therefore preferred rather than HCl. CH3ONa obtained an optimal reaction

time in 20 seconds with an average yield of FAMEs equalling 80% ± 17. Since CH3ONa

obtains a similar yield more rapidly than BF3 it is therefore more suitable as a catalyst in

microwave assisted transesterification.

In addition, it was investigated if microwave assisted transesterification with BF3 could result

in higher yield of FAMEs and shorter reaction time compared to a traditional method. The

traditional method involved the transesterification of triglycerides at room temperature with a

base catalyst, CH3ONa. The average yield of FAMEs obtained was 80% ± 17. Compared with

microwave assisted transesterification the yield was similar but the standard deviation and

RSD for the microwave method was somewhat lower. Since the microwave method is overall

shorter in duration, it is more beneficial.

An improvement of a method for acid catalysed microwave assisted methylation of even and

odd numbered free fatty acids from C4:0 to C18:0 was performed. This improvement

involved the use of ice baths after the metylation reaction to minimize loss of FAMEs with

chain length < C10:0. In addition, this method was compared with conventional heating methods by water baths. Even though ice baths was employed in both methods, continued loss

of FAMEs with chain length C4:0-C9:0 was observed, indicating that the employed system

was insufficiently closed.

A study of hydroxy fatty acid methyl esters' (OH-FAMEs) stability on GC-MS was performed

to investigate if these compounds can be detected and quantified with GC-MS. All OHFAMEs

analyzed was also detected, with the exception of 12-OH-FAMEs. Quantification

could not be performed because of wide and unsymmetrical peaks with low intensities
Publisher
Norwegian University of Life Sciences, Ås

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