ANALYTICAL cHEMISTRY - Iv

Experiment 7

Principle

• Fats are one of the three main macro-nutrients along with carbohydrates and proteins. Fat molecules consists of primarily carbon and hydrogen atoms and are therefore hydrophilic and thus soluble in organic solvents and insoluble in water. Examples include cholesterol, phospholipids and triglycerides.

• Fat is an important foodstuff for many forms of the life and fats serve both structural and metabolic functions. Some fatty acids that are set free by the digestion of fats are called essential because they cannot be synthesized in the body from simpler constituents. Fats and other lipids (it is a general term though a lipid is not necessarily a triglyceride) are broken down in body by enzymes called lipases produced in pancreas. Fats and oils are categorized according to the number and bonding of carbon atoms in the aliphatic chain. Fats that are saturated have no double bonds between the carbons in the chain. Unsaturated fats have one or more double bonded carbons in the chain. Most fats are glycerides, particularly triglycerides.

Soxhlet extraction:

• An extraction is feasible even when the components of interest have an unfavorable partition coefficient, provided that all other components in the sample have significantly smaller partition coefficients. Because the partition coefficient is unfavorable, a simple extraction will not be quantitative. Instead, the extraction is accomplished by continuously passing the extracting phase through the sample until a quantitative extraction is achieved.

• Many continuous extractions involving solid samples are carried out with a soxhlet extractor. The extracting solvent is placed in the lower reservoir and heated to its boiling point. Solvent in the upper reservoir moves upwards through the tube on the left side of the apparatus to the condenser where it condenses back to the liquid state. The solvent then passes through the sample which is held in a porous cellulose filter thimble, collecting in the upper reservoir. When the volume of solvent in the upper reservoir reaches the upper bend of the return tube, the solvent and any extracted components are siphoned back to the lower reservoir. Over time, the concentration of the extracted components in the lower reservoir increases.Principle

• Fats are one of the three main macro-nutrients along with carbohydrates and proteins. Fat molecules consists of primarily carbon and hydrogen atoms and are therefore hydrophilic and thus soluble in organic solvents and insoluble in water. Examples include cholesterol, phospholipids and triglycerides.

• Fat is an important foodstuff for many forms of the life and fats serve both structural and metabolic functions. Some fatty acids that are set free by the digestion of fats are called essential because they cannot be synthesized in the body from simpler constituents. Fats and other lipids (it is a general term though a lipid is not necessarily a triglyceride) are broken down in body by enzymes called lipases produced in pancreas. Fats and oils are categorized according to the number and bonding of carbon atoms in the aliphatic chain. Fats that are saturated have no double bonds between the carbons in the chain. Unsaturated fats have one or more double bonded carbons in the chain. Most fats are glycerides, particularly triglycerides.

• Soxhlet extraction:

• An extraction is feasible even when the components of interest have an unfavorable partition coefficient, provided that all other components in the sample have significantly smaller partition coefficients. Because the partition coefficient is unfavorable, a simple extraction will not be quantitative. Instead, the extraction is accomplished by continuously passing the extracting phase through the sample until a quantitative extraction is achieved.

• Many continuous extractions involving solid samples are carried out with a soxhlet extractor. The extracting solvent is placed in the lower reservoir and heated to its boiling point. Solvent in the upper reservoir moves upwards through the tube on the left side of the apparatus to the condenser where it condenses back to the liquid state. The solvent then passes through the sample which is held in a porous cellulose filter thimble, collecting in the upper reservoir. When the volume of solvent in the upper reservoir reaches the upper bend of the return tube, the solvent and any extracted components are siphoned back to the lower reservoir. Over time, the concentration of the extracted components in the lower reservoir increases.

• Principle

• Fats are one of the three main macro-nutrients along with carbohydrates and proteins. Fat molecules consists of primarily carbon and hydrogen atoms and are therefore hydrophilic and thus soluble in organic solvents and insoluble in water. Examples include cholesterol, phospholipids and triglycerides.

• Fat is an important foodstuff for many forms of the life and fats serve both structural and metabolic functions. Some fatty acids that are set free by the digestion of fats are called essential because they cannot be synthesized in the body from simpler constituents. Fats and other lipids (it is a general term though a lipid is not necessarily a triglyceride) are broken down in body by enzymes called lipases produced in pancreas. Fats and oils are categorized according to the number and bonding of carbon atoms in the aliphatic chain. Fats that are saturated have no double bonds between the carbons in the chain. Unsaturated fats have one or more double bonded carbons in the chain. Most fats are glycerides, particularly triglycerides.

• Soxhlet extraction:

• An extraction is feasible even when the components of interest have an unfavorable partition coefficient, provided that all other components in the sample have significantly smaller partition coefficients. Because the partition coefficient is unfavorable, a simple extraction will not be quantitative. Instead, the extraction is accomplished by continuously passing the extracting phase through the sample until a quantitative extraction is achieved.

• Many continuous extractions involving solid samples are carried out with a soxhlet extractor. The extracting solvent is placed in the lower reservoir and heated to its boiling point. Solvent in the upper reservoir moves upwards through the tube on the left side of the apparatus to the condenser where it condenses back to the liquid state. The solvent then passes through the sample which is held in a porous cellulose filter thimble, collecting in the upper reservoir. When the volume of solvent in the upper reservoir reaches the upper bend of the return tube, the solvent and any extracted components are siphoned back to the lower reservoir. Over time, the concentration of the extracted components in the lower reservoir increases.

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Apparatus required

Soxhlet apparatus, Round bottom flask, Porcelin pieces, Condenser, Filter paper, Whattmann filter paper No. 1, etc.

Chemicals required

200 ml petroleum ether, 3 g of crushed chips, etc.

About the sample:

Name and brand:

Manufacturing date:

Bought from:

Result

% Fat in chips (by difference of filter paper) = _______ %.

% Fat in chips (by difference of round bottom flask) = _______ %.

Reference Material

1. G H Jeffery, J Bassett, J Mendham and R C Denney, Vogel's Textbook of Quantitative Chemical Analysis, 5th Edition

2. S. Suzanne Nielsen, Food analysis, 4th Edition

Questions