Dhristi JEE 2022-24

Chemical Analysis - Classification, Classical and Instrumental Methods

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 practice methods. Separation is the process of isolating analytes. Quantitative analysis decides the numerical quantity or concentration, while qualitative analysis defines analytes.

 

Chemical analysis is performed collectively by a team of experts with extensive knowledge of specialized techniques such as infrared absorption, emission spectroscopy, electrochemistry, or gas chromatography, and considerable knowledge of the capabilities of the method. Used by other team members. Therefore, an analytical chemist is not a chemist who measures the chemical composition of a substance. He now takes two more steps in the analysis process to solve the problem. One is the beginning (problem definition) and the other in the end (troubleshooting). This means that analytical chemists can measure anything but a well-defined chemical composition. For example, you might decide that measuring pH is better than analyzing the final product for process control. The metal surface is more important than composition determination.

 

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

 

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 the physical property of the analyte.

 

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 colored 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.

2.   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 based on the property of the analyte to be tested. Many of the techniques apply neighboring 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 neighboring 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.

 

Precipitation Analysis

Cations are generally classified according to their properties into one of six groups and anions into one of three groups. The details of the classification vary slightly from source to source. Each group has a common reagent that can be used to separate cations or anions in solution. Separations must be performed in a specific order to achieve meaningful results. This is because some ions from the former group may react with reagents from the latter group. This is because cation analysis is based on ionic solubility products. When the cations reach the desired optimal concentration, they are precipitated for detection. Copper in the precipitation analysis wire displaces silver, silver is immersed in silver nitrate solution, and precipitates solid silver. Sediment analysis can be used to determine the chemical composition of a solution. The cationic group includes:

 

Cation forms insoluble chlorides such as lead, silver, and mercury. Formation of acid-insoluble sulfides such as cadmium, bismuth, copper, antimony, and tin. With the formation of insoluble hydroxide complexes such as iron, aluminum and chromium.

 

Adding ammonia chloride, ammonium hydroxide, and hydrogen sulfide gases to zinc, nickel, cobalt, and manganese will determine the element. The colour of the sediment indicates the metal. Insoluble carbonate group. (Many initial cations precipitate as carbonate, but will be detected up to this point if you follow the steps in a certain order.) Barium, calcium, and strontium precipitate at this point, but not earlier. Magnesium, lithium, sodium, potassium, and ammonium are difficult to precipitate and are usually identified by the colour of the flame. There are three groups of negative ions, and there are several ways to detect them. However, deposition methods such as those mentioned above are often used.

 

Colorimetric Analysis

Using a coloured reagent, colorimetric analysis measures the concentration of a chemical in a solution. Inorganic and organic compounds are examined in this way. In medical laboratories and industrial water treatment, this method is widely used to analyze water samples. 

 

What are the Similarities Between Qualitative Analysis and Quantitative Analysis in Chemistry?

Chemical analysis can be categorized as either qualitative or quantitative. Chemical analyses both qualitatively and quantitatively reveal details about sample components. The quantitative and qualitative methods are often applied in conjunction with each other. The main analytical method in chemistry for quantifying and qualitatively determining the chemical composition of a sample is Qualitative and Quantitative Chemical Analysis.

 

Uses of Chemical Analysis:

  1. As a result, analytical chemistry has a vital role in medicine, as it can be used to determine the amounts of ingredients such as carbohydrates, lipids, proteins, and sugars in the body. As well as determining levels of toxic wastes in the body, such as uric acid, cholesterol, drugs, and certain salts, analytical methods can help determine levels of toxic wastes in the body.

  2. Identifying unknown substances and matching samples to known substances is a task for forensic chemists when they analyze abiotic samples found at crime scenes. Furthermore, we identify and sometimes quantify drug/regulated substances found in the field of human beings.

 

Did You know?

The measurement of the interaction of infrared radiation with 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 on Chemical Analysis

1. What are the traditional methods of separation?

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.

2. What methods do you use to examine chemicals?

The following steps are needed to examine chemicals:

  • Sampling 

  • Field Sample Pretreatment 

  • Laboratory Procedure 

  • Laboratory Assay 

  • Measurements 

  • Results Presentation

 

 For the analytical result to be accurate, each step must be completed correctly.

3. What is the Purpose of Chemical Analysis?

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.

4. Difference between Qualitative and Quantitative analysis.

Analyzing Chemistry qualitatively and quantitatively is fundamentally different, as the qualitative analysis indicates the presence or absence of various chemical components, but quantitative analysis indicates the concentration of these chemical components in a given sample.

5. What kind of Chemical Analysis Equipment do you have?

Instruments used for the detection, analysis, and measurement of chemicals include:

  • Spectroscopic systems such as MS, Atomic Absorption, Atomic Emission, UVVIS, X-ray, and Raman scattering.

  • Gas system and liquid chromatography including HPLC and solid-phase extraction.

  • Process Analyzer with NIR.

  • Refractometer, Rheometer, Viscometer, Evaporator, Thermal Analyzer, and Calorimeter.

  • Pump from high-pressure syringe pump to peristaltic pump.

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