Quantitative Chemical Analysis

Introduction to Quantitative Chemical Analysis

Quantitative chemical analysis is the method of determining the absolute or relative abundance of one, several, or mostly all particular substances that are present in a sample. It is widely used in analytical chemistry and the methods that come under this umbrella are used to conduct scientific experiments, and also determine various industrial production aspects. The properties that are used to determine the quantitative analysis chemistry are both physical and chemical properties. The most common description of the quantitative analysis chemistry is given by the concentration of the ore. 

Different Methods of Quantitative Analysis

The study of the absolute and relative abundance in a given sample, for the determination of the specific properties of certain substances present in the sample. For best use of quantitative analysis chemistry and chemical, methods have been developed so much that there are numerous methods and techniques to identify and characterize any sample quantitatively. Although there are numerous methods and techniques developed, knowing a sample or the composition of the sample is of significant importance to eliminate any possible tests for further characterisation. Two of the common classifications under which various methods of analysis which students can also find in any textbook of quantitative chemical analysis. They are classified as under:

  • Gravimetric Analysis: These are a set of different methods that are used to determine the characteristics of an analyte based on the mass. The principle that works behind these methods is that when an analyte’s mass is known or determined as a unique singular entity the known value of the mass then it can be used to determine the mass of the analyte in a mixture, as long as relative quantities of other analytes in the mixture is known. 

  • Volumetric Analysis: These are the set of methods that involve the concept of concentration of a particular analyte in a solution. The main principle in these methods is the functioning of a known reaction and the result of the reaction. A known compound that induces a particular reaction leading to an end product is used for measurement of the concentration of the unknown in the solution. 

The methods used in the gravimetric analysis techniques provide more accurate results and more accurate data for the composition of the sample. The drawback is that it takes a long time to analyse samples based on the gravimetric methods. This is in contrast to the volumetric methods of quantitative analysis analytical chemistry provides for. The quantitative inorganic analysis is mostly based on the concepts of the concentration such as molarity and their relation to volumes and provides satisfactory results within a short period of time. The volumetric analysis is simply a titration reaction that can either produce neutralised salt products, precipitates, complexes, or redox products which can be obtained instantly or in a much lesser time as compared to the gravimetric analytical methods. 

The benefit of quantitative chemical analysis is that they are very generalised in nature. They can be applied to understand a wide range of analytes especially while performing quantitative inorganic analysis. Examples of some of these general characteristics of the methods are stated below:

  • Neutralisation Reaction: A reaction between an acid and a base produces salt and water as products. This is known as a neutralisation reaction. 

  • Precipitation Reaction: A reaction in which the end result is a highly insoluble complex or compound that falls out of the solution and precipitates is known as a precipitation reaction. The standard solution widely used in these methods is silver nitrate that is used as a reagent for the reaction. These methods are also known as argentometry. 

  • Complex Reaction: These titration reactions that occur in-between the metal ions and a standard solution give products that are complexes of the metal ion. In most cases, the standard solution that is used is the EDTA (Ethylene Diamine Tetra Acetic Acid). 

  • Redox Reaction: Redox titration reaction is carried out in between an oxidising agent and a reducing agent.

Other examples of methods that are part of the quantitative chemical analysis are the Leibig method or Duma’s method or Kjeldahl’s method and the Carius method for the estimation of the organic compounds. These quantitative analysis methods can also be applied for the mass spectrometry on the biological samples that can be determined by the relative abundance of the ratio of the specific proteins, and indications of diseases like cancer. 

Other Analytical Methods in Chemistry

The other most common and fundamental methods in chemistry are the qualitative analytical methods. Students, as they learn, will study methods included in both the qualitative and quantitative analysis chemistry class has to offer. The qualitative methods are used for the determination of the quality of a sample and a particular analyte in a sample. The IUPAC (International Union of Pure and Applied Chemistry) defines both the quantitative and qualitative methods as follows:

“The general expression Quantitative Analysis [...] refers to the analysis in which substances are identified or classified on the basis of their chemical or physical properties, such as chemical reactivity, solubility, molecular weight, melting point, radioactivity properties (emission, absorption), mass spectra, nuclear half-life, etc.  Quantitative Analysis refers to analyses in which the amount or concentration of an analyte may be determined (estimated) and expressed as a numerical value in appropriate units. Qualitative Analysis may take place with Quantitative Analysis, But Quantitative Analysis requires the identification (qualification) of the analyte.For which numerical estimates are given.”  

Spectroscopy techniques such as IR (Infra-red) spectroscopy or UV (Ultra-violet) spectroscopy are used to understand and assert the qualitative properties of a sample. It can also be very accurately determined in the ranges of micro-molars or nano-molars using methods of NMR (Nuclear Magnetic Resonance). 

FAQs (Frequently Asked Questions)

1. What is Quantitative Chemical Analysis?

Ans: Quantitative chemical analysis is a branch of chemistry that deals with determining the mass of an analyte present in a mixture or a solution depending on the chemical and/or physical properties like chemical reactivity, solubility, molecular weight, etc. Thus in simple terms, the methods in this branch deal with identifying the quantity of a particular substance in a given mixture or a solution. The chemical methods that are included in these reactions include precipitation, neutralization, oxidation-reduction, etc. 

2. What is a Quantitative Analysis Example?

Ans: Quantitative analysis is the determination of the mass or concentration of a particular substance in any given compound, solution or mixture. With respect to that, the examples of quantitative analysis include the determination of concentration in a given solution by using the concept of molarity as it is obtained by the ratio of the weight of the given solute to its molecular weight per litre of solution. Thus, having known the specifics of the concentration of a given sample, one can obtain the amount/mass of the solute present in the solution.