Experiment 3

Objective :

To determine amount of each fatty acid in oil and fat samples using gas chromatography (GC).

Abstract

Introduction

i.Gas Cromatography

A gas chromatograph is an instrument used to separate samples in a complex formed. A gas chromatograph uses a flow-through narrow tube known as the column, through which different chemical constituents of a sample pass in a gas stream or mobile phase at different rates depending on their various chemical and physical properties and their interaction with a specific column filling, called the stationary phase. As the chemicals exit the end of the column, they are detected and identified electronically by a detector. The function of the stationary phase in the column is to separate different components, causing each one to exit the column at a different time. Other parameters that can be used to alter the order or time of retention are the carrier gas flow rate, and the temperature.

ii.Standard

Fats consist of glycerol ester and long chain aliphatic acids (fatty acids). The general glycerol ester structure is shown below:

CH2-O-CO-R1

CH –O-CO-R2

CH2-O-CO-R3

The backbone of these compounds contains from 4 to more than 20 carbon atoms. Most natural sources of these compounds have an even number of carbon atoms because the biosynthetic pathway builds the backbone two carbons at a time.

Fatty acid chain may contain one or more double bonds at specific positions (unsaturated and polyunsaturated), or the may be fully saturated. The physical and chemical properties of a fat depend on the composition of the fatty acid mixture. Animals’ fats tend to have a larger proportion of long chain saturated acids and are solids at room temperature. Fats from plant sources contain a higher proportion of unsaturated acids and are often liquids at room temperature due to hydrogen...