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The role of analytical chemistry. Analytical methods.






Analytical chemistry is applied throughout industry, medicine, and all the sciences. To illustrate, consider a few examples. The concentrations of oxygen and of carbon dioxide are determined in millions of blood samples every day and used to diagnose and treat illnesses. Quantities of hydrocarbons, nitrogen oxides, and carbon monoxide present in automobile exhaust gases are measured to determine the effectiveness of emission-control devices. Quantitative measurements of ionized calcium in blood serum help diagnose parathyroid disease in humans. Quantitative determination of nitrogen in foods establishes their protein content and thus their nutritional value. Analysis of steel during its production permits adjustment in the concentrations of such elements as carbon, nickel, and chromium to achieve a desired strength, hardness, corrosion resistance, and ductility.

The mercaptan content of household gas supplies is monitored continually to ensure that the gas has a sufficiently obnoxious odor to warn of dangerous leaks. Farmers tailor fertilization and irrigation schedules to meet changing plant needs during the growing season, gauging these needs from quantitative analyses of plants and soil.

The interdisciplinary nature of chemical analysis makes it a vital tool in medical, industrial, government, and academic laboratories throughout the world.

Analytical chemistry achieves the aims by various methods of analysis:

I. Physical – determination of components of investigated substances without chemical reactions (destroying of sample):

1. Spectral analysis – investigation of emission and absorption spectra.

2. Fluorescence analysis – investigation of luminescence, caused action of UV-radiation.

3. Roentgen-structural analysis – using X-ray.

4. Mass-spectra analysis.

5. Densimetry – measurement of density.

II. Instrumental (physical-chemical) – based on measurement of physical parameters (properties) of substances in run of chemical reaction. This method divides on

1.Electrochemical – measurement of electrical parameters of electrochemical reactions.

2. Optical – investigation the influence of various electromagnetic radiation on substance.

3. Thermal (heating) – investigation the changes the properties of substance by heat (undergo) action.

III. Chemical – measurement of chemical bonds energy.

Chemical analysis has some steps:

1. Sampling.

2. Dissolving the sample (in water, acid or alkali).

3. Executing (running) the chemical reaction X + R → P.

4. Measurement of definite parameter.

In accordance to analytical reaction (X + R → P) applies three groups of chemical analysis methods:

Measurement of amount (quantity) of reaction product P: mass, physical properties.

Measurement of amount of reagent R that interacted with determined substance: volume of solution reagent R with known concentration.

Registration changes of substance X acting with reagent: measurement of gas volumes.


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