A Simple Note on Qualitative Analysis

Qualitative analysis

In both Organic and Inorganic Chemistry, qualitative analysis is an important aspect of chemical analysis. It gives an indication of the chemical compound’s quality. 

The goal of qualitative analysis is to ascertain the makeup of an unknown sample or to identify the components or elements within it. Quantitative analytical questions cannot be answered precisely using qualitative methods.

Noting that a reaction produces gas that bubbles out of solution or observing that a reaction causes a colour change are two examples. 

Although qualitative analysis is not as trustworthy as quantitative analysis, it is frequently much easier, faster, and less expensive to conduct.

Qualitative analysis in organic chemistry

Qualitative analysis is used to determine and characterise organic molecules once they have been produced in their purest form. The analysis provides information on the chemical’s ingredients. 

The most common components found in organic molecules are carbon, hydrogen, oxygen, and nitrogen (in rare situations), which are detected through analysis. Sulphur, halogens, metals, and phosphorus are sometimes discovered and detected via qualitative analysis.

For example

Nitrogen can be detected in organic moieties using the following techniques:

• When an organic component is extensively burned and produces a burnt hair or feather odour, a dry heating test shows the presence of nitrogen. However, because many nitrogen-containing compounds do not produce odour, the test has limitations.
• Soda-lime test: A small quantity of the organic substance is heated strongly with soda lime () in a dry test tube. If the vapours have an ammonia-like odour, nitrogen is present.

Qualitative analysis in inorganic chemistry

This covers qualitative analysis in the laboratory as well as the anion and cation analysis technique. 

It gives a general review of inorganic qualitative analysis, as well as the equipment, reagents, and techniques that will be used in the laboratory. 

The classification of precipitates, handling precipitates, separation procedures, flame tests, Brown ring tests, and solvent extraction are all part of the preliminary investigations. 

It also explains how to set up an experiment for anion and cation analysis, such as testing for water solubility in a solid sample or treating a water-soluble material with sodium carbonate.

Methods for qualitative analysis

There are namely 5 methods by which we can determine the components present in a particular compound. They are mentioned below:

• Physical methods: these methods include the shape, size, colour etc.
• Separation methods: chromatography is one way to separate components present in a compound.
• Chemical methods: Chemical reactions employed in qualitative analysis typically fall into one of two categories:
  • Reactions of neutralisation
  • Oxido-reductive reactions
  • Reaction of complexation.
  • Reaction of precipitation.
• Biological methods: these include processes like immunoassays etc.
• Spectro-photometric methods: These are the most advanced qualitative analysis and control methods available. They are more accurate, quick, and simple to use than previous approaches like UV, x-ray etc.

Sensitivity and specificity

A qualitative analytical method has two distinct properties. It should be both particular and delicate. 

The ability to recognise a certain component or element in the presence of additional components is referred to as specificity. 

The ability to detect the testing element, even if it is present in trace amounts, is referred to as sensitivity. 

In other words, sensitivity refers to the smallest amount of an element or compound that technology can detect. Some procedures are extremely sensitive, and others require a relatively high concentration for detection. 

Quantitative analysis

Quantitative analysis is a chemical procedure for determining the amount of each component present in a substance. It can be done in a classical or instrumental manner.

A quantitative examination would determine the mass or relative mass of each component contained in a sample made up of two or more substances. It is not always required to obtain quantitative numbers for all of a substance’s constituents.

Conclusion

As it does not measure anything that can be described in numbers, the qualitative chemical analysis might be considered as a beginning point for a thorough analysis of a substance (e.g., mass). People also might want to know how much of the chemical has been identified. A supplementary analysis approach, quantitative chemical analysis, can be utilised in this circumstance.