Skip main navigation

£199.99 £139.99 for one year of Unlimited learning. Offer ends on 28 February 2023 at 23:59 (UTC). T&Cs apply

Find out more

The chemical analyses

Chemical analyses, their methods and their information content.
In this VIDEO lesson we will show you the basis of analytical chemistry, with the aim of learning some key concepts and basics of this science. Chemical analyses are usually performed by modern, complex and expensive instruments which … ..take advantage of some chemical and physical characteristics of the analyte. The analyte is the molecule of interest. Chemical instruments require operators are high-qualified personnel There are several techniques suitable for almost every kind of molecule and analysis. The two main questions analytical chemistry answers are “what is in there ?” and “how much of each is in there ?”, these two main approaches are called… … qualitative and quantitative analyses.
With the qualitative analyses we need to identify and distinguish the red, yellow, grey, green and light blue balls in the mixture. Instead with the quantitative analyses we can “count” the red, green and yellow balls, and say HOW MANY of EACH. Every analytical instrument reports the presence of chemical species with a signal on a screen which can take the shape of a line, or a colour or a number; the technical name is A SPECTRUM However, how can we state what this spectrum corresponds to? Chemi-Joe teaches us that we have to use a reference molecule to compare the signal obtained with the analyte.
The reference molecule is called “standard” or “standard reference”… … and is essential for the identification of a chemical species in analysis. Furthermore, if we use varying growing concentrations of analytical standard we can also draw a calibration curve, that is used to quantify the unknown concentration of our analyte by its signal intensity. That’s the way! Lets spend a couple words on the kind of analysis that the analytical lab is capable of performing. There are routine analysis which are performed often and without particular efforts, and non routine analysis which are done “on demand” and equire a deeper understanding of the analyte and where it comes from.
A routine analysis can be the quantification of a pesticide residue in water samples, or vitamin-D in the blood. A non routine analysis is for example the quantification of a toxicant or a drug in a sample coming from autopsy, or ONE SPECIFIC protein involved in a metabolic pathway. Now, back to main topic. What can we practically analyze? Let’s focus on a daily object -guess what- a food packaging. Starting from the raw materials to the finished products - and all what’s in the middle - chemical analyses offer a robust capability to assess their safety and if they respect the requested standards.
The questions are : is the plastic used toxicant free ? Is this production batch compliant with the limits imposed by law on plasticizers ?
We can ask Chemy-Joe: is this enough for a packaging product? as you learn in the previous activity, in some cases … …. if a material undergoes a thermal or mechanical shock, some chemicals are able to migrate from the Food Contact Material into the food or drinks. Joe teaches us that “in this case a Chemist works as a criminal investigator, searching for traces and clues. His work is to backtrace where these molecules come from and, collaborating with biologists and epidemiologists, if this chemical is harmful.
The issue of migration is gaining growing attention from regulatory agencies and safety controllers mostly for the difficulty in characterizing what and how much comes from the package A migration assay usually is carried out by analyzing the food product after being kept in contact with the FCM in stressful conditions Once a molecule is identified, results can be informative as we find something that we know is present in the packaging item, such as terephthalate,
which is a known plasticizer: In this case we can backtrace every step in the production chain and find the critical moment when migration most probably took place. Not all the migration analyses are informative.
For example: a new chemical found in a new plastic packaging, without any previous indication of its effects and origin, is just a a signal registered on an instrument. The chemical information in this case has no much value and its, therefore, little informative Therefore, regulations must be introduced, based on experimental data and biological trials.. And for this purpose, scientists and material producers MUST communicate and assure the safety of the commercialized product. To conclude, you have learned : 1: what quantitative and qualitative terms mean, regarding chemical analyses 2: what is a “standard” 3: the main analytical applications 4: What is migration and how can we run a migration assay

In this video lesson you will learn about the basics of chemical analyses applied to the detection of unwanted chemicals. You will see some instruments and methods, you will see how to build a standard curve, you will understand how chemical analyses can be informative or non informative, and finally you will begin to observe chemical migration. This video is a bit technical, but trust us that will be very useful.

This article is from the free online

Consumer and Environmental Safety: Food Packaging and Kitchenware

Created by
FutureLearn - Learning For Life

Our purpose is to transform access to education.

We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.

We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.

Learn more about how FutureLearn is transforming access to education