Quantitative Analysis

Quantitative analysis is a chemical analysis performed to find the amount of each component present in a material. It is done by either a classical or instrumental procedure.

A quantitative investigation means that the amount (quantity) or relative amount of each component present is determined. In a pure substance, the entire mass, or 100%, is composed of a single component. In materials composed of two or more substances, a quantitative investigation would determine the mass or relative mass present for each component within the sample. It is not always necessary to find quantitative values for all components that make up a substance. In most cases it is sufficient to analyze the material for one or perhaps more components of interest. The amount of active medicine within an antacid tablet, for example, is significant, whereas the fillers, binders, colorants, and flavoring agents present are of lesser importance.

A quantitative analysis involves more than simply measuring the amount of a component present in a sample

The sample must first be prepared for measurement, usually by placing it in solution if it is not already in soluble form. With complex substances a preliminary separation of the desired component is often necessary to prevent other substances present from interfering with the selected analytical method.

An analyst is one who measures the components of a material quantitatively as a percent or amount present in a sample. Analysts are employed by manufacturing industries to test the reliability of their products. If an automobile manufacturer, for example, specifies that the iron content of the steel used in an automobile is of a certain percentage, then this value must be checked constantly by the manufacturer to see that the automobile meets specifications. This repeated checking is known as quality control and manufacturing facilities have a quality control department employing analytical chemists. Hospitals, too, employ analytical

chemists to test patients for proper amounts of medication. Athletes are subjected to quantitative testing to determine the presence and amount of possible illicit drugs in their bodies. The federal government carries out frequent quantitative measurements of environmental samples. Should, for example, a company generate greater amounts of a pollutant than is allowed by law, then the government can fine the company or force it to close until it meets government regulations. Legislators at the local, state and national level use quantitative results to formulate laws that prevent the general public from coming into contact with dangerous amounts of harmful chemicals in food, medicine, the environment, and other areas.

Various methods are employed to undertake a quantitative investigation. These methods are broadly classified as classical and instrumental methods.