is by far the most widely used from of chromatography , particularly by organic chemists, and it undoubtedly ranks as one of the most important analytical techniques since its development in 1952. the separation of benzene, and cyclohexane is extremely simple by gas chromatography, but virtually impossible by conventional distillation.

In gas chromatography, the sample is converted to the vapor state and eluent is a gas. The stationary phase is generally a nonvolatile liquid supported on inert solid such as firebrick or diatomaceous earth. There the mobile phase that different separations are accomplished.

The sample is automatically detected as it emerges from the column, the sampling side relative to the reference side signal is fed to recorder where the chromatography peak are recorded as a function of the time. By measuring the retention time and comparing with standard of the pure substance, it may be possible to identify peak the area under the peak is proportional to the concentration and so the amount of substance can be quantitatively determined.

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Kung khao (Litopenaeus Vannamei) have fatty acid about 0.43-0.49%, such as ω-6 fatty acids (20:4 n6) ω-3 fatty acids that’s eicosapentaenoic acid (EPA) and docosahexaenoic acid ( DHA )

Khung khao are cleaned and dehulled then chop to mince

Lipid were extracted by the chloroform-methanol ( 2:1,v/v )

Crude lipid 100 mg were saponified by using

1 ml of 0.5 NaOH in Methanol

and heated for 15 min at 80C.

The saponifiable matter was then eterified

by using 2ml of BF3 ( 12% in methanol )

for 5 min at 80C

Fatty acid methyl ester was dilute in hexane by using 1 ml of hexane for 1 min at 80C

then cooling and add 3ml of saturated NaCl,stirring and pipette the hexane out

Add and remove hexane against for three more time. Storage the product in vial at -15C.

Columm : 15% DEGS on Chromosorp 80/120w

Columm Temp : 150C

Detector : FID

Carrier gas : N2

Detector temperature : 150C

Standard Fatty acid : Supelco No.47045 : C17 and C18

Fatty acid methyl ester were identified by comparing the retention time against the standard.

Fig 1. Chromatographic profile of n-Heptadecanoic acid

( C17 ) and Tri-stearin ( C18 ).

Fig 2. Total ion Chromatograms of profile of Peneusmerguiiensis lipid sample .

Weight of shrimp ( g )

Total fatty acid extracted ( g )

% of C18 in total fatty acid extracted

% of fatty acid C18 in shrimp ( w/w )

20.13 0.36 29.26 0.52

Gas Chromatography technique is importance and rapid and accuracy method for food science when need to detected on isolate compound in food. More ever this technique due amount of sample are in limit.