Ever seen someone wee in a pool?
We don't recommend it - besides being impolite, weeing in a pool is injurious to health. The acid in urine reacts with chlorine (used to sanitise swimming pools) and produces toxic gaseous products, which can irritate our lungs and damage our respiratory system.
So, how do you think that scientists studied this chemical reaction? They collected samples of pool water contaminated with urine to understand the risks of weeing in pools. Then, they separated and tested the samples, all so that they could identify the compounds within. Next, they studied the compounds to understand how they react and impact our health. All of this distils down to one field of chemistry: chemical analysis.
- This article is about chemical analysis.
- First, we will look into the definition of chemical analysis
- Then we will have a brief explanation of how chemical analysis is done, and the steps involved in it.
- Then, we will dive into the types of chemical analysis: qualitative and quantitative analysis.
- After that, we'll explore different techniques, methods, and tests used in chemical analysis. This includes instrumental methods.
- Finally, we will understand the importance of chemical analysis.
Definition of chemical analysis
Is it possible to identify the presence of urine in a pool just by looking at it? No! Likewise, we cannot see the toxic products that urine produces on reacting with chlorine. To identify them in the pool water, we use chemical analysis.
Chemical analysis is the process of identifying, separating and quantifying the components of a sample to understand its nature and composition. The branch of chemistry that deals with chemical analysis is called analytical chemistry.
There are different types of chemical analysis, as well as various common techniques and methods. But before we jump into them, let us have a brief look at the steps of chemical analysis.
Steps of chemical analysis
No matter the method or technique used, chemical analysis typically involves the following steps:
- Collecting a sample of interest.
- Picking an appropriate analytical method to analyse the sample.
- Prepping the sample.
- Analysing the sample using your chosen method, test, or technique.
- Interpreting the results of the analysis. This might involve calculations or further tests.
These steps give us a brief overview of how chemical analysis is done. Each step might have further sub-steps and include unique analytical procedures. The choice of analytical techniques or methods used depends on our sample and the type of chemical analysis we want to carry out. Let's explore the types of chemical analysis now.
Types of chemical analysis: qualitative and quantitative
Chemical analysis is classified into two major types
- Qualitative chemical analysis.
- Quantitative chemical analysis.
We'll first have a look into qualitative chemical analysis.
Qualitative chemical analysis
You taste a pizza and might feel it is too hot for your taste. What makes the pizza so spicy? Maybe it is topped with jalapeños, or perhaps pepperoni? These toppings help give the pizza its unique taste and identity.
Fig. 1: Supreme pizza.
Therefore, to determine why a pizza tastes a certain way, we try to identify what it is topped with. This is a kind of qualitative analysis.
Qualitative chemical analysis is a type of analysis used to identify the substances within a sample and determine whether a particular substance is present or not.
Just like the toppings of a pizza, all the chemical samples have different constituents within them. To determine the constituents of a chemical sample, we use qualitative chemical analysis. It tells us exactly which chemical species the sample is made from, be it different molecules, elements, or compounds.
Quantitative chemical analysis
Let us consider the example of pizza again. We know that the toppings like jalapeños and pepperoni make a pizza taste hot. But how do we know how much pepperoni is added to a pizza? This question is how much of something is answered by quantitative chemical analysis.
Quantitative chemical analysis is a type of analysis used to determine the quantity or the amount of a substance in a sample.
Why might quantitative chemistry be useful? Well, what if you like a little bit of heat on your pizza, but not too much? You'd probably prefer a pizza topped with just a few slices of pepperoni. Knowing exactly how much pepperoni will be in your meal allows you to pick the perfect pizza for you.
In short, qualitative analysis deals with what is present in a sample, while quantitative analysis answers how much of the substance is there.
Chemical analysis: tests, methods, and techniques
For your GCSE exam, you need to know about different techniques, tests, and methods used in chemical analysis. You should be able to compare them as well as discuss why you might choose one approach over another. Here is an introduction to chemical analytical techniques:
Testing for pure substances using melting and boiling points.
Testing for gases using simple test tube reactions.
Testing for ions using reactions that you can carry out in class, such as flame tests, the sodium hydroxide test, and tests for anions.
Instrumental analysis, such as chromatography and flame emission spectroscopy.
Fig. 2: A diagram showing the colours of flames produced by different ions, an example of qualitative analysis.
Instrumental analysis
The tests for gases and the sodium hydroxide test are all simple reactions that you can try out in class. They are quick and convenient to use, but they are qualitative, not quantitative. If we want a quantitative measure of the sample, we have to use certain analytical instruments. They not only identify components of a sample, but also measure their relative amounts. Using analytical instruments in chemical analysis is called (no surprises here) instrumental analysis.
Instrumental methods have certain advantages over test tube reactions. As mentioned above, some are both qualitative and quantitative, whilst most are extremely accurate, sensitive and rapid. In addition, they can work with small samples and are highly versatile.
Here are some examples of instrumental analytical techniques:
- NMR, IR, UV, x-ray fluorescence, and flame emission spectroscopy are all types of spectroscopic techniques. They use the interactions between electromagnetic (light) waves and particles to help us identify the structure of atoms and molecules.
- Chromatography works by separating a sample into its components. As well as paper chromatography, which you'll learn about in your GCSE chemistry course, you can find thin-layer chromatography, gas chromatography, gas-liquid chromatography, and many other variations! For example, if you want to separate a mixture of amino acids, you typically use paper or thin layer chromatography.
Check out Instrumental Analysis to learn more about instrumental techniques used in chemical analysis. Additionally, you can explore some of the specific methods we mentioned above at A-level chemistry. Why not explore NMR Spectroscopy or Chromatography to find out further details about the respective subjects?
Examples of chemical analysis
Every household product, from toiletries like shampoo and soap to food products like table salt, sugar, and sauces, is chemically analysed before it reaches you to ensure that it is non-toxic, stable, and safe to use. Given below are a few examples of the fields in which chemical analysis is used and some of its uses that you might encounter.
Field | Uses of chemical analysis | Example |
Medicine | | |
Food | | |
Environmental science | | |
Sports | | |
Chemical Analysis - Key takeaways
Chemical analysis is the process of identifying, separating and quantifying a substance in a sample.
There are two types of chemical analysis:
- Methods and techniques used in chemical analysis include tests for gases, testing for ions, and instrumental analysis.
- You find examples of chemical analysis in areas of everyday life such as medicine, the food industry, and sport.
References
- Josh Fischman, 'Don't Go in the Water: The Chemistry of Pee in the Pool [Video]'. Scientific American (10/06/2014)
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