Analytical Chemistry

Analytical chemistry is the study and application of instruments and methods for separating, identifying, and quantifying matter. Separation, recognition, and quantification can be used alone or in combination with other methods in practice. Separation is the process of isolating analytes. Quantitative analysis decides the numerical quantity or concentration, while qualitative analysis defines analytes.


On this page, we will study the classical method, instrumental methods of chemical analysis, and chemical analysis techniques.


Classification of Analytical Methods

Classical, wet chemical methods and modern instrumental methods make up analytical chemistry. Separations such as precipitation, extraction, and distillation are used in classical qualitative methods. Colour, odour, melting point, boiling point, solubility, radioactivity, and reactivity can all be used to identify a substance. Quantitative analysis that uses mass or volume adjustments to measure quantity is known as traditional quantitative analysis. Chromatography, electrophoresis, and field-flow fractionation are some of the instrumental methods that can be used to separate samples.


To conduct an analysis, the majority of traditional analytical methods rely on chemical reactions. Instrumental methods, on the other hand, usually rely on the calculation of a physical property of the analyte.

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Classical Method

For Qualitative Analysis:

  • In classical qualitative analysis, one or more chemical reagents are added to the analyte. The identity of the analyte can be determined by studying chemical reactions and their components. The added reagents are selected to react selectively with one or a single class of chemical compounds to produce a distinct reaction product. In certain cases, the reaction product is a precipitate, a gas, or a coloured substance.

  • Take, for example, copper(II), which reacts with ammonia to form a deep blue copper-ammonia complex. Similarly, dissolved lead(II) reacts with chromate-containing solutions to produce yellow lead chromate. The same method can be used to qualitatively test negative ions (anions) and positive ions (cations). A common example is a reaction between carbonates and strong acids, which results in the formation of carbon dioxide gas bubbles.

The Classical Method of Analysis for Organic or Inorganic Analyte:

  • The analyte is classified as organic or inorganic in most cases. As a result, qualitative analysis is classified as organic or inorganic. Inorganic compounds mainly contain elements other than carbon, whereas organic compounds primarily contain carbon compounds. Sugar (C12H22O11) is an organic compound, while table salt (NaCl) is an inorganic compound.

  • Chemical reactions between added chemical reagents and functional groups of organic molecules are involved l in classical organic qualitative research. As a result, the assay's result provides information about a portion of the organic molecule but typically does not provide enough information to fully classify it. To classify the entire molecule, other measures such as boiling points, melting points, and densities are combined with a functional group analysis.

  • The reaction between bromine in a carbon tetrachloride solution and organic compounds containing carbon-carbon double bonds is an example of a chemical reaction that can be used to classify organic functional groups. Owing to the addition of bromine through the double bonds, the distinctive red-brown colour of bromine vanishes, indicating the existence of a carbon-carbon double bond.

For Quantitative Analysis:

Gravimetric and volumetric analysis are two types of traditional quantitative analysis. Both approaches rely on lengthy chemical reactions involving the analyte and additional reagents.

  1. Gravimetric Analysis

A precipitate is formed when an excess of added reagent reacts with the analyte. The filtrate is measured after it has been washed, dried, and weighed. The concentration or quantity of the assayed material in the analyte is calculated using its mass.

  1. Volumetric Analysis

The titrimetric analysis is another name for volumetric analysis. From a buret, the reagent (the titrant) is progressively or stepwise applied to the analyte. The secret to good titrimetric analysis is to consider the titration's equivalence point (the point at which the quantities of the two reacting species are equivalent), which is usually visible as a colour transition.


Instrumental Methods of Analysis

Chemical analysis instrumental methods are classified into groups based on the property of the analyte to be tested. Many of the techniques are applicable to both qualitative and quantitative research.


Classification of Instrumental Methods of Analysis

Spectroscopy

Spectroscopy is a technique for determining how molecules deal with electromagnetic radiation. Spectroscopy encompasses a wide range of techniques, including atomic absorption spectroscopy, atomic emission spectroscopy, ultraviolet-visible spectroscopy, x-ray spectroscopy, fluorescence spectroscopy, infrared spectroscopy, Raman spectroscopy, dual-polarization interferometry, nuclear magnetic resonance spectroscopy, and photoemission spectroscopy. Some of the spectroscopy is discussed below.

  1. Nuclear Magnetic Resonance

Different spectral regions of absorption correspond to different physical processes occurring within the analyte. In the presence of a magnetic field, absorption of energy in the radiofrequency region is sufficient to cause a spinning nucleus in certain atoms to shift to a different spin state. As a result, nuclear magnetic resonance spectrometry may be used to determine the number and types of various nuclei present in the groups attached to the atom containing the nucleus under investigation. It's particularly useful for analyzing organic compounds qualitatively.

  1. Atomic Absorption Spectroscopy

Atomic absorption spectroscopy (AAS) and atomic emission spectroscopy (AES) are Spectro analytical procedures that use the absorption of optical radiation (light) by free atoms in the gaseous state to determine chemical elements quantitatively. The absorption of light by free metallic ions is the basis for atomic absorption spectroscopy.


The technique is used in analytical chemistry to determine the concentration of a certain element (the analyte) in a sample to be analyzed.

  1.  Ultraviolet-Visible Spectrophotometry

UV–Vis spectroscopy, also known as ultraviolet-visible spectrophotometry (UV–Vis or UV/Vis), is the study of absorption and reflectance spectroscopy in the ultraviolet and visible regions of the electromagnetic spectrum. This means it makes use of visible and neighbouring light.

  1. Fluorescence Spectroscopy

Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is an electromagnetic spectroscopy technique for analyzing fluorescence in a sample. It entails the use of a beam of light, generally ultraviolet light, to excite the electrons in certain compounds' molecules and cause them to emit light; normally, though not always, visible light.

  1. Magnetic Resonance Spectroscopy

The spectroscopic technique of nuclear magnetic resonance spectroscopy, also known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is used to observe local magnetic fields around atomic nuclei. The Nuclear magnetic resonance signal is provided by excitation of the nuclei sample with radio waves into nuclear magnetic resonance, which is detected with sensitive radio receivers, and the sample is placed in a magnetic field. The resonance frequency of an atom in a molecule is changed by the intramolecular magnetic field surrounding it, allowing access to knowledge of the molecule's electronic structure and individual functional groups. 


The spectroscopic technique of nuclear magnetic resonance spectroscopy, also known as Nuclear magnetic resonance spectroscopy or magnetic resonance spectroscopy (MRS), is used to observe local magnetic fields around atomic nuclei. The NMR signal is provided by excitation of the nuclei sample with radio waves into nuclear magnetic resonance, which is detected with sensitive radio receivers, and the sample is placed in a magnetic field. The resonance frequency of an atom in a molecule is changed by the intramolecular magnetic field surrounding it, allowing access to knowledge of the molecule's electronic structure and individual functional groups.


Electrochemical Analysis

The potential (volts) and/or current (amps) in an electrochemical cell containing the analyte are measured using electroanalytical methods. These techniques are classified based on which aspects of the cell are regulated and which are calculated. Potentiometry (measuring the difference in electrode potentials), coulometry (measuring the transferred charge over time), amperometry (measuring the cell's current over time), and voltammetry (measuring the cell's current while actively altering the cell's potential) are the four major groups.


Thermal Analysis

The interaction of a substance and heat is measured using calorimetry and thermogravimetric analysis.


Separation

Separation methods are used to make content mixtures less complicated. This field includes chromatography, electrophoresis, and field flow fractionation.


Microscopy

In analytical science, visualization of single molecules, single cells, biological tissues, and nanomaterials is an effective and appealing approach. Analytical science is now being revolutionized by the hybridization of other conventional analytical methods. Optical microscopy, electron microscopy, and scanning probe microscopy are the three different types of microscopy. Because of the rapid growth of the computer and camera industries, this sector has recently accelerated.


Did You Know?

The measurement of the interaction of infrared radiation with the matter by absorption, emission, or reflection is known as infrared spectroscopy (IR spectroscopy or vibrational spectroscopy). It's used to investigate and classify chemical compounds or functional groups that exist in solid, liquid, or gaseous forms. Infrared spectroscopy is a process or technique that uses an instrument called an infrared spectrometer (or spectrophotometer) to obtain an infrared spectrum. A graph of infrared light absorbance (or transmittance) on the vertical axis vs. frequency or wavelength on the horizontal axis may be used to image an IR spectrum.

FAQs (Frequently Asked Questions)

Q1. What are the Traditional Methods of Separation?

Ans: Separations such as precipitation, extraction, and distillation, as well as qualitative analysis by colour, odour, or melting point, are used in traditional methods (also known as wet chemistry methods). The materials are separated using chromatography or electrophoresis techniques.

Q2. What Methods do You Use to Examine Chemicals?

Ans: The following steps are needed to examine chemicals:

  1. Sampling 

  2. Field Sample Pretreatment 

  3. Laboratory Procedure 

  4. Laboratory Assay 

  5. Measurements 

  6. Results Presentation

 In order for the analytical result to be accurate, each step must be completed correctly.

Q3. What is the Purpose of Chemical Analysis?

Ans: Chemical testing and analysis are important for regulatory enforcement as well as understanding the consistency and composition of chemical substances and materials used in products, production processes, and industrial processes.