EXPERIMENT 1 DETERMINATION OF FATTY ACIDS IN COOKING OIL BY USING GAS CHROMATOGHRAPHY
OBJECTIVE :
1. To determine the fatty acids contain in cooking oil (corn oil and palm oil) by using gas
chromatography
2. To learn on how to operate gas chromatography instrument
INTRODUCTION
Gas chrom chromato atogra graphy phy is a term term used used to descr describe ibe the separa separatio tion n techniques used to analyses olatile substances in the gas phase. !n gas chromatography" the components of a sample are dissoled in a solent and apori#ed in order to separate the analytes by distributing the sample between two phases which are stationary phase and mobile phase such as helium helium or hydro hydrogen gen.. The mobile mobile phase is a chemi chemical cally ly inert inert gas that seres seres to carry carry the molecules of the analyte through through the heated column. column. The liquid stationary phase is adsorbed onto a solid inert packing or immobili#ed on the capillary tubing walls in a thin layer. $ typical gas chromatograph consists of an in%ection port" a column" carrier gas &ow control equipment" oens and heaters for maintaining temperatures of the in%ection port and the column" an integrator chart recorder recorder and a detector. detector.
'atty $cids are aliphatic carboylic acid with arying hydrocarbon lengths at one end of the chain %oined to terminal carboyl (*++,) group at the other end. The general formula is -(*, 2)n*++,. 'atty acids are predominantly predominantly unbranched and those with een numbers of carbon atoms between 12 and 22 carbons long react with glycerol to form lipids which is fatsoluble
components
of
liing
ce l l s
in
plants"
animals"
and
microor microorganis ganisms. ms. The ob%ecties ob%ecties of this eperiment eperiment are to determine determine the fatt fatty y acid acids s that that cont contai ain n cook cookin ing g oil oil by using sing gas gas chr chromat omatog ogra raph phy y instrument and to learn the operation of gas chromatography itself.
MATERIALS
1. Gas chromatography
. /ethanol
2. *apillary column
0. ipette
. etroleum ether (G* grade)
3. 4orte mier
5. 6tandard fatty acids (palmitic acid" stearic acid 8. 6odium hydroide (9a+,)
7. Glass ial
1. 6ample (*orn oil and
alm oil)
METHODS
$.
reparation of 6odium /ethoide -eagent 1.18 g of sodium hydroide was dissoled in 8 m; methanol
<.
reparation of the 6tandard 1. 3 ppm concentration of each fatty acids was prepared by dissoling .3 g in 1 m; petroleum ether 2. The standard prepared was then shake well by using the orte miture . .5 u; of the sample was in%ected into the G* in%ector port. The present of bubbles was =rst remoed during drawing in the sample into the syringe and the thumb was positioned oer the syringe plunger to preents a blowback of the sample by the carrier gas pressure in the in%ection port
*.
reparation of the 6ample 1. .8 g of sample was weighed into a 2 m; olume glass ial 2. 7.8 m; petroleum ether was added by using a graduated pipette and the ial was closed and shake well to make sure the sample was dissoled . .8 m; of sodium methoide was added by using glass pipette and the ial was closed immediately. The ial was then shake igorously for 1 seconds by using orte miture
5. The miture was leaed for 2 minutes and the present of clear upper layer that formed was obsered 8. The clear upper layer was then pipette out into a clean and dry ial for analysis . .5 u; sample was in%ected into the G* in%ector port carefully
RESULTS
$.
-ecord of retention time and peak area data eak $rea (cm)
-etention time (t-) 6tandard
T T- 1
T- 2
(aerag
$ 1
$ 2
1.88
180.17
180.
1.5
018.
501.82
e) 6tearic $cid almitic $cid
1.857
1.803
1.3
1.515
6ample
TT- 2
(aerag
$cid
*orn +il alm +il
almiti c $cid
*orn +il alm +il
1.2
1.22
1.83
1.17
1.517
1.51
1.01
1.515
1.228 1.1 1.5108 1.728
8 87.87
$ 1
$ 2
$ (aerag e)
1230.3
22.53
18.03
35 8885.
3 0723.08
32 051.7
13
5 1137.3
51 70.103
055.1
05 183.28
1 5781.5
21
3
58
e) 6tearic
120.7
eak $rea (cm)
-etention time (t-) T- 1
$ (aerage )
5.78
CALCULATION
-esponse 'actor -esponse 'actor (-f ) > *oncentration ? eak $rea
1. 6tearic acid methyl ester -esponse 'actor (-f )
> 3 ppm ? 120.78 cm2
> .283 2. almitic aid methyl ester -esponse 'actor (-f )
> 3 ppm ? 87.87 cm2
> 2.222
*oncentration *oncentration (ppm) > -etention 'actor (-f ) eak $rea (cm2)
1. alm +il a) 6tearic acid methyl ester *oncentration (ppm) > .283 051.751 > 557.12 ppm b) almitic acid methyl ester *oncentration (ppm) > 2.222 5781.558 > 1122.33 ppm
2. *orn +il a) 6tearic acid methyl ester *oncentration (ppm) > .283 18.03321 > 1700.88 ppm b) almitic acid methyl ester *oncentration (ppm) > 2.222 70.1031 > 21.57 ppm
DISCUSSION
Through this eperiment" the fatty acids contained in cooking oils which
are palm oil
and
corn oil
was determined
by using gas
chromatography. The standard (palmitic acid methyl ester and stearic acid methyl ester) was prepared =rst into desired concentration which is 3 ppm before it was in%ected to G* in%ector port. The samples was then prepared appropriately and leaed for 2 minutes until clear upper layer was formed before it was also in%ected to G* in%ector port. The retention time and peak area data was then recorded and the result was analysed.
'rom the results" the retention time of standard fatty acids was compared with unknown samples (corn oil and palm oil) to identify types of fatty acid present. -etention time plays big role in analysing the sample in the gas chromatography. $ccording to @irasnita et. al" (21) retention time are diAerentiated according to the number of carbon" molecular weight and the boiling point of the samples. The retention time will increase when the molecular weight and boiling point of the compound increased.
respectiely. This result shows the nearest t- alue to the stearic acid methyl ester standard (1.88). !n contrast" the others aerage t- alue for corn oil and palm oil are 1.5108 and 1.728 respectiely. This data shows the nearest t- alue to palmitic acid methyl ester standard (1.5).
/eanwhile" response factor (-f ) for each standard was calculated which are .283 for stearic acid methyl ester and 2.222 for palmitic acid methyl ester. The response factors were calculated by using this formula: -esponse 'actor (-f ) > *oncentration ? eak $rea The response factor for each standard was then used to calculate the concentration of the appropriate fatty acids in the samples (corn oil and palm oil) by using this formula: *oncentration (ppm) > -etention 'actor (-f ) eak $rea (cm2)
'rom the results obtained" the concentration of palmitic acid in corn oil and palm oil are 21.57 ppm and 1122.33 ppm respectiely. /eanwhile" the concentration of stearic acid in corn oil and palm oil are 1700.88 ppm and 557.12 ppm respectiely. These results show that palm oil and corn oil contain higher number of stearic acid than palmitic acid. !n addition" corn oil also show that it contain higher number of stearic acid contain than palm oil. These results were not corresponding with the actual result that was based on studies. This was maybe due to seeral errors during preparation. $ccording to Cambiaki et. al (21)" palm oil should contain a lot of palmitic acid (*1) than stearic acid (*13) as the peak area aerage data of palmitic acid in palm oil has the highest alue than in corn oil which results in higher concentration of fatty acid through the concentrationBs calculation.
During the eperiment" they are some sources of error that occur which may aAect the accuracy of the result. 'or eample" there are paralla error that happen when the eyes does not directly proportional to
the reading of the syringeBs measurement. The present of bubbles during drawing in the sample into the syringe might also interrupt the G* readings. The preparation of standard might be contaminated.
To minimi#e these errors arious precautions should be taken such as" make sure our eyes are directly proportional during reading the measurement in the syringe" the syringe was rinsed and cleaned by using pet ether before and after each sample was used to preent any contaminant from others solution that will aAect the data obtained and the formation of bubbles was aoided from aAecting the reading in the column. To add on" the standard should be freshly prepared. ;astly" three consecutie of measuring need to be carried out to eliminate the errors of the handlers.
CONCLUSION
!n conclusion" the fatty acids contained in cooking oil (corn oil and palm oil) were determined which are stearic acid and palmitic acid by using gas chromatography. alm oil and corn oil also was found to contain a lot of stearic acid than palmitic acid.
REFERENCE
-. @irasnita" T. ,adibarata" E. /aria 9oelina" $.E. -ahim" and C. Eusop" (21)" $ /odi=ed
/ethylation
*ontent by Gas *hromatography"
/ethod to -etrieed
Determine
$pril
"
'atty
21
$cid
from
=le:???*:?Fsers?user?Downloads?/odi=ed2/ethylation2rocess 2and2D
etermination2of2'atty2$ccid.pdf
-. *. Cambia#i" -. r#ybylski" /. @. Cambia#i and *. <. /endonca" (21)" 'atty $cid *omposition of
4egetable +ils and 'ats" -etrieed Hun 28"
21 from http:??www.nononsensecosmethic.org?wp content?uploads?218?1?fattyacidoil
composition.pdf
4esna I. " 6. /emeti and <.
http:??www.%hed.mk?=lemanager?H,JD
24ol25?2.2'?.2'ull2pap 2Iostik22.pdf
er2
24esna
