Quantitative Analysis: Definition, Methods, Advantages

Quantitative analysis

Quantitative analysis is a branch of chemistry concerned with determining the amount or percentage of one or more elements in a sample. In chemistry, quantitative analysis determines the amount of various chemical components contained in a given sample. Quantitative chemical analysis is utilized for diagnostic purposes, such as determining biochemical markers in biopsied tissues. Similarly, forensic scientists may utilize chemical analysis to reconstruct a murder scene and investigate chemical clues such as poison traces in food. The quantitative examination of organic components also allows us to synthesize natural substances with commercial applications. However, A combination of approaches is frequently required for analysis: qualitative analysis for distinguishing desirable constituents from a sample and quantitative analysis for determining the amounts present.

Methods of quantitative analysis

The quantitative chemical analysis seeks to ascertain the amounts or percentages of elements in a sample. To investigate the composition of samples, many approaches are utilized. For quantitative analysis, a variety of methodologies are used. These are broadly classified into two types: physical methods and chemical procedures.

The primary purpose of quantitative analysis is to measure or compute the proportions of a substance’s essential constituents (elements or functional groups). Some methods display measurements immediately, while others require mathematical skills to calculate the solution.

Chemical methods of quantitative analysis

Chemical methods of quantitative analysis rely on reactions such as precipitation, neutralization, oxidation, or the production of a new chemical in general. The advantage of quantitative chemical analysis is that it is highly generic in nature. They can be used to comprehend a wide spectrum of analytes, particularly when doing quantitative inorganic analysis. Some of these general properties of the approaches are illustrated below:

Neutralization reactions

When an acid and a base react, salt and water are produced as byproducts. This is referred to as a neutralization reaction.

Complexometric reaction

This reaction involves the reaction between the metal ion and the complexing agent in the presence of an appropriate indicator is present. The indicator is a complexing agent as well, but it should combine with metal ions to produce a less stable complex and impart different unique colors during complexation and decomplexation. A mixture of various metal ions in a solution can be determined with the help of complexometric titrations. The end-point of the titration is typically identified using an indicator that can cause an unambiguous color shift.

Precipitation reaction

A precipitation reaction is a process that produces an extremely insoluble complex or compound that precipitates out of the solution. The element to be identified is precipitated from a solution using this method of analysis with the addition of a suitable precipitating agent. The precipitate should either have a known composition or, through heating, should be changed into another compound with a known composition.

 In a precipitation titration, the titrant and analyte combine to create a precipitate, an insoluble material. It continues until all of the analytes have been consumed. Examples of such titrations are often limited to those involving the precipitation of silver ions with anions like halogens or thiocyanate (SCN). 

Oxidation-reduction reaction

An oxidation-reduction reaction usually involves the occurrence of oxidation and reduction events simultaneously. In a chemical process, the species undergoing oxidation is often referred to as the reducing agent, while the species undergoing reduction is commonly referred to as the oxidizing agent. Electrons are exchanged between two chemical species in redox reactions. One species, in particular, acts as an electron donor and suffers oxidation, whereas the other acts as an electron acceptor and experiences reduction.

 However, Gravimetric analysis and volumetric, or titrimetric analysis are the two main categories of exclusively chemical approaches.

Gravimetric analysis

A quantitative method for determining an analyte based on the mass of a solid is known as gravimetric analysis. Using this method of analysis, the element to be detected is precipitated from a solution by the addition of a suitable precipitating agent. The precipitate should either have a known composition or be converted into another compound with a known composition through heating. Gravimetric analysis is based on the idea that the mass of an ion present in a pure compound can be calculated by estimating the mass percentage of the same ion in a known quantity of an impure compound. The methodologies utilized in gravimetric analysis techniques provide more accurate results and data regarding the sample’s composition. The disadvantage is that gravimetric procedures take a long time to analyze samples.

Titrimetric analysis

Titrimetric analysis is an analytical technique that involves measuring the volume of a reagent that is stoichiometrically interacting with the analyte. The titrimetric analysis is also referred to as the volumetric analysis. The volumetric analysis calculates the volume of a known concentration solution required to completely react with the analyte.

Volumetric analysis is a titration process that can yield neutralized salt products, precipitates, complexes, or redox products instantly or in considerably less time than gravimetric analytical procedures. Quantitative inorganic analysis is primarily based on concentration principles such as molarity and their relationship to volumes, and it produces satisfactory results in a short period of time.

Physical Methods of Quantitative Analysis

 Physical methods of quantitative analysis involve measuring physical properties such as density, refractive index, light absorption or polarisation, electromotive force, magnetic susceptibility, and many others. Some physical methods include:

Fourier Transform Infrared spectroscopy (FTIR)

FTIR involves the transmission of IR photons through a material. The infrared radiation passes through the sample and is transferred after being partially absorbed by the sample. The resulting spectrum provides a molecular fingerprint for the sample by illustrating the molecule’s absorption and transmission. Like fingerprints, no two distinct chemical structures develop the same infrared spectrum. As a result, infrared spectroscopy can be used for a wide range of examinations.

Atomic emission spectroscopy (AES)

Atomic emission spectroscopy (AES) is a technique for quantifying metal atoms by measuring the intensity of light emitted by the atoms in excited states. The study of the wavelengths of photons produced by atoms and molecules as they shift from a high-energy state to a low-energy state is the fundamental concept of atomic emission spectroscopy. Atomic emission spectroscopy examines the radiation emitted by atoms to determine their structure, composition, and environment.

AES is used to determine the amounts of Na+ and K+ ions in the human body, which are required for a variety of metabolic processes. These chemicals’ concentrations can be determined by diluting and aspirating a blood serum sample into the flame.

Energy-dispersive X-ray spectroscopy (EDS)

Energy-dispersive X-ray spectroscopy (EDS) is a strong technique that allows the user to determine the elemental composition of a sample. In this method, an electron beam is focused toward a sample substance, energizing the electrons in an inner shell. This causes electrons to be ejected, releasing energy in the form of X-rays. This, in turn, can reveal a substance’s atomic identity or identity.

Trace element analysis (TEA)

Trace element analysis (TEA) involves several techniques used to determine the amount of trace elements in a sample. It’s especially helpful in ecology and toxicology. X-ray fluorescence (XRF), atomic absorption spectroscopy (AAS), neutron activation analysis (NAA), and proton-induced X-ray emission (PIXE) are some examples of trace element analysis techniques.

Advantages of quantitative analysis

  • Quantitative analysis allows you to predict how much product to expect and calculate your actual yield.
  • Since it is used to evaluate nutritional levels and give a precise accounting of dosage, quantitative analysis is essential to the development and testing of food and medicines.
  • It is also important for determining the quantity of pollutants or impurities in a sample.
  • It also has a variety of practical applications. Quantitative analysis, for example, is used in medical diagnostics, such as analyzing cholesterol levels in a patient’s blood.
  • It is also used in the formulation of medicines and the processing of food goods.
  • It is used to quantify or calculate the proportions of fundamental constituents (elements or functional groups) in a substance.
  • Quantitative tests are performed to ensure that items meet the specifications of the producer or the regulatory authorities.
  • It specifies how much reactant should be required to execute a chemical synthesis process in order to obtain a specific amount of product, reducing chemical waste (increasing atom economy).
  •  It can be used to assess the quality of food or any other product by demonstrating the existence of sufficient levels of constituents.
  •  It can be used to determine the purity of a sample.

References

  • https://www.britannica.com/science/quantitative-chemical-analysis.
  • https://www.differencebetween.com/difference-between-qualitative-and-vs-quantitative-analysis-in-chemistry/.
  • https://byjus.com/chemistry/quantitative-analysis/.
  • https://www.thoughtco.com/definition-of-quantitative-analysis-604627.
  • https://chem.libretexts.org/Bookshelves/General_Chemistry/Chemistry_1e_(OpenSTAX)/04%3A_Stoichiometry_of_Chemical_Reactions/4.5%3A_Quantitative_Chemical_Analysis.
  • https://www.vedantu.com/chemistry/quantitative-chemical-analysis.

About Author

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Kabita Sharma

Kabita Sharma is a graduate student from the central department of chemistry, Tribhuvan University. She has been actively involved in research related to natural products, computational chemistry, and nanochemistry. She is currently working on enzyme assay, molecular docking, and molecular dynamic simulation.

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