Atomic Absorption Spectroscopy

Atomic absorption spectroscopy (AAS) is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state.

In analytical chemistry the technique is used for determining the concentration of a particular element (the analyte) in a sample to be analyzed. AAS can be used to determine over 70 different elements in solution or directly in solid samples used in pharmacology, biophysics and toxicology research.

Atomic absorption spectroscopy was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.^[1]

The modern form of AAS was largely developed during the 1950s by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, inMelbourne, Australia.

Atomic absorption spectrometry has many uses in different areas of chemistry such as:        

·         Clinical analysis: Analyzing metals in biological fluids and tissues such as whole blood, plasma, urine, saliva, brain tissue, liver, muscle tissue, semen

·         Pharmaceuticals: In some pharmaceutical manufacturing processes, minute quantities of a catalyst that remain in the final drug product

·         Water analysis: Analyzing water for its metal content.

1) WHAT IS A PHYTOCHEMICAL?

Phytochemicals are chemical compounds that occur naturally in plants. Some are responsible for color and other organoleptic properties, such as the deep purple of blueberries and the smell of garlic. The term is generally used to refer to those chemicals that may have biological significance, for example carotenoids or flavonoids, but are not established as essential nutrients.

2) WHAT IS PHYTOCHEMICAL SCREENING?

Phytochemical screening - is a process of tracing plant constituents. For example you want to found out if a certain plant contains alkaloids (a plant constituent) then, you will be performing a phytochemical screening procedures for alkaloids (in this case mayer's and Wagner's test). There are general plant constituents that can be performed with a standard test.

3-5 WHAT ARE THE DIFFERENT REAGENTS USED IN PHYTOCHEMICAL SCREENING? HOW ARE THESE REAGENTS PREPARED? WHAT ARE THE INDICATORS OF THE PRESENCE OF EACH PHYTOCHEMICAL?

Alkaloids

5 mL od Mayer's reagent were added to 5 mL of the pure extract. Formation of yellow recipitataes indicates the presence of Alkaloids.

B. Carbohydrates

2.5 mL of Molisch's reagent were added to 5 mL of the pure extract. Formation of red or purple ring indicates presence of carbohydrates.

C. Glycosides

2.5 mL of acetic acid and ferric chloride mixture was added to 5 mL of the pure extract. Presesnce of blue-green color indicates the presence of glycosides.

D. Saponins

10 mL of distilled water was added to 5 mL of the pure extract. The mixture was shaken in a graduated cylinder for 15 minutes. Presence of layer of foam or bubbles indicates presence of saponins.

E. Phenols

5 mL of water was added to 5 mL of the pure extract. Then, ferric chloride drop was also added, formation of blue or light green color indicates presence of Phenols.

F. Tannins

5 mL of ferric chloride solution was added to 5 mL of the pure extract. Formation of dark blue or greenish-black color indicates presence of tannins

G. Anthocyanin

2.5 mL of Sodium hydroxide solution was added to 5 mL of the extract. Formation of blue or green precipitates indicates presence of anthocyanin.

H. Protein

2.5 mL of nitric acid was added to 5 mL of the pure extract. Formation of yellow color indicates presence of protein.

I. Flavonoids

5 mL of Sodium hydroxide solution was added to 5 mL of the extract. Formation of orange or intense yellow color indicates the presence of flavonoids.