Quantitative analysis in chemistry focuses on the precise measurement of chemicals and the associated parameters. It’s an integral part of chemistry, both in terms of pure science and practical applications.
Chemistry is classed as a ‘hard’ science due to its high level of precision and accuracy. For example, chemistry analysis allows us to determine the exact molar values of solutes in a mixture. It can also help identify initially unknown variables or parameters for a wide range of applications.
Quantitative chemical analysis, for instance, is used for diagnostic purposes, such as determining the biochemical markers in biopsied tissues. Likewise, forensic scientists may use chemical analysis to reconstruct a crime scene and examine chemical clues, such as traces of poisons in food. The quantitative analysis of organic compounds also enables us to synthesise natural chemicals that have commercial values, for example, fragrances and flavours.
From finding rich sources of mineral ores to synthesising medicines and measuring pollution, quantitative analysis plays a central role in a variety of applications.
In this post:
What is Quantitative Analysis in Chemistry?
Integral to all natural sciences, quantitative analysis measures specific parameters of a data set and makes calculations. In chemistry it may refer to quantitative chemical analysis, which is part of analytical chemistry. The other method of chemical analysis is known as qualitative analysis.
Quantitative chemical analysis aims to determine the percentage or proportions of constituents in a sample. Various methods are used to examine the constituents of samples. These are generally divided into two categories – physical methods and chemical methods.
Their main goal is to measure or calculate the proportions of fundamental constituents (elements or functional groups) in a substance. Some methods directly show the measurements while others require mathematical skills to calculate the answer.
Why is Quantitative Analysis Important in Chemistry?
Quantitative analysis is important in chemistry for many reasons. Not only is it integral to the pursuit of pure science, but it has various practical applications, too. For example, quantitative analysis is used for medical diagnostic purposes, such as measuring cholesterol levels in a patient’s blood. It also plays a role in formulating medicines and processing food products.
Furthermore, quantitative analysis can help companies to comply with environmental regulations. It can determine the amount of pollution a factory emits, for example. The mining and petroleum industries also use quantitative analysis to identify the best sites to dig.
Examples of Quantitative Analysis in Chemistry
Physical methods primarily analyse the energy output of atoms. Examples of physical methods in quantitative analysis include:
- Fourier Transform Infrared Spectroscopy (FTIR) – this approach uses the infrared wavelength in the electromagnetic spectrum. Specific wave frequencies of infrared are absorbed or emitted differently by various substances, depending on their constituents. FTIR can determine various functional groups that have certain signatures based on the infrared range.
- Atomic Emission Spectroscopy (AES) – this method relies on the optical emission of energised molecules to determine the type and concentration of the constituent atoms. A sample substance is subjected to very high levels of energy, such as a high-voltage electric arc that turns gas into plasma. The energy forces the atoms to emit light, which is then analysed and compared to elements or compounds with known light emission spectrum.
- Energy Dispersive X-ray Spectroscopy (EDS) – in this example an electron beam is directed at a sample substance, thereby energising the electrons in an inner shell. This leads to the ejection of electrons, which releases energy in the form of x-ray. In turn, this can reveal the atomic identity or identities of a substance.
- Trace element analysis – otherwise known as TEA, this term describes a group of techniques used to determine the amount of trace elements in a sample. It’s particularly useful in ecology and toxicology. Some examples of TEA techniques include x-ray fluorescence (XRF), atomic absorption spectroscopy (AAS), neutron activation analysis (NAA) and proton-induced x-ray emission (PIXE).
Chemical methods mainly focus on analysing chemical reactions. Some examples of chemical methods of quantitative analysis include:
- Titration – otherwise known as volumetric analysis, titration is commonly used when analysing the proportion of an analyte solute to its solvent. It’s especially useful in analysing neutralisation reactions between acids and bases.
- Gravimetric analysis – in this method, a sample substance is weighed and the constituents are then isolated through chemical reactions. The desired products may be isolated through various means such as filtration and centrifuge. The weight of the isolated substance is then compared to the original sample substance.
- Combustion analysis – this technique is primarily used for analysing the empirical and molecular formula of hydrocarbons. The products of complete hydrocarbon combustion are always carbon dioxide and water. These products are separated and isolated in absorbent materials that are weighed before and after the reactions. You can then calculate the proportion of hydrogen and carbon.
How to Write a Quantitative Data Analysis Report in Chemistry
The exact format of writing a quantitative data analysis report depends on several factors. One of these variables is the target audience.
For instance, is it a school report or will it be published in a scientific journal for experts? The format may also vary depending on the organisation. A chemical manufacturing company, for example, may require a different format from an environmental organisation.
That said, the generic format often includes the following:
- Cover page
- Abstract or summary of the findings
- Tabulated data and graphs
- A conclusion that interprets the data
Which Branch of Chemistry Specifically Deals with Quantitative Analysis?
Analytical chemistry involves both quantitative and qualitative analysis. This branch of chemistry is primarily focused on determining the constituents of substances. Fields that apply analytical chemistry extensively include:
- Environmental science
Bonus: Qualitative Chemistry
Qualitative chemistry analysis is also part of analytical chemistry and may be used as a precursor to quantitative methods.
It focuses on determining the presence or absence of certain substances and is less arduous than qualitative analysis. The use of colour indicators is the best example of qualitative chemistry.
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