Food Fraud in Australia?

Congratulations to Dr Michael Smith, Associate Professor Mahmud Ashraf, Professor Chris Austin
and Associate Professor Rebecca Lester of  Deakin University on the publication of "Product fraud: Impacts on Australian agriculture, fisheries and forestry industries" (November 2021). This report gives a good, concise, overview of known recent agricultural product fraud from all over the world. While it can make for scary reading, it is a reminder to stay vigilant when buying food. Here is a little taste of what you will find in the report,

"Turmeric is considered highly vulnerable to food fraud, with
frequent incidents of contamination with lead chromate (a
yellow colourant) reported. A study found that seven of nine
turmeric-growing areas in Bangladesh showed evidence
of turmeric adulteration with lead chromate. Levels of lead
exceeded national limits by up to 500 times (24-9-19)."

You can download a copy of the report at the AgriFutures Australia website: https://www.agrifutures.com.au/product/product-fraud-impacts-on-australian-agriculture-fisheries-and-forestry-industry/

Examples of food fraud can be used when teaching chemistry. Students can calculate the concentration of milk or fruit juice after it has been fraudulently diluted, and then compare that to what is stated on the nutrition panel product label. You can learn a lot about the properties of chemical compounds and mixtures by making a fake egg or fake milk. You could used the adulteration of "manuka honey" to teach spectroscopy, or the melamine (1,3,5-triazine-2,4,6-triamine) in milk scandal to teach percentage composition or volumetric analysis. The pedagogical possibilities are limited only by the resourcefulness of the food fraudsters.

If you are looking for some more inspiration, try "Sorting the Beef from the Bull: The Science of food fraud forensics" (Evershed, R., and Temple, N, 2017). And yes, I may have bought it because it has such a great title ... you all know me too well 😉

 

Precipitation Titrations

Have you ever tried to determine the chloride concentration in a water sample using gravimetric analysis? It's pretty tricky! There must be a better way .....
There is .... precipitation titrations (also known as argentimetric titrations or argentometric titrations).
AUS-e-TUTE has just added a new tutorial, game, test, exam and practical activity on this topic for members.
If you are not a member, you can access a "free-to-view" tutorial at
 https://www.ausetute.com.au/pptitration.html

Precipitation Conductometric Titrations

If you have an aqueous salt solution it conducts electricity because of all the ions in the solution. If you add a different aqueous salt solution to this it is possible that a precipitate will form, effectively removing some of the ions in solution so it should be possible to monitor changes in the electrical conductivity of a solution during a precipitation reaction to determine the equivalence point of the reaction. This is known as a precipitation conductometric titration (or as a conductometric precipitation titration) and AUS-e-TUTE has just added a new tutorial, game, test and exam to help our members understand this!
If you are not an AUS-e-TUTE Member, you can currently access a "free-to-view" tutorial on this topic at https://www.ausetute.com.au/conductpptn.html

Gravimetric Analysis

Gravimetric analysis can be used to determine the quantity of an ion present in a solution.
This can be done by adding a reagent that causes the ion under investigation to form an insoluble compound (a precipitate) that precipitates out of the solution.
AUS-e-TUTE has "free-to-view" tutorials currently available on :

1.  Determining the percentage by mass of sulfate in a lawn fertiliser
2.  Determining the concentration of chloride ions in water

AUS-e-TUTE Members should log-on to go to the Members ONLY resources on these topics which include:

• tutorials
• games
• tests (with worked solutions)
• exams (with worked solutions)

Not an AUS-e-TUTE Member?
Contact us to get access to the interactive demonstration resources.

Lipstick Evidence

Lipstick is sticky stuff!
Kissing someone on the cheek with your lusciously lipsticked lips will invariably leave a colourful impression. And, after you've had your sip of coffee your "lips" are left behind in vivid colour on the cup. Lipstick can even end up on tissues after  a momentary touch as you blow nose, or wipe tears from your eyes. And we've all seen movies in which a wife discovers lipstick (not her own) on her husband's collar. Needless to say then that lipstick can be found at a crime scene and is considered to be an example of "trace evidence".
Researchers at  Western Illinois University have been investigating better ways to lift and analyse this lipstick evidence.
In general, lipstick is composed of

•     65% castor oil
•     15% beeswax
•     10% other waxes
•     5% lanolin (also known as wool wax or wool grease)
•     5% dyes, pigments and perfume

In other words, most of the mass of a lipstick is made up of lipids (fats, oils and waxes).
To lift the lipstick from the material, the researchers developed a two part process:

1.   Add an organic solvent to remove most of the oils and waxes.
2.   Add a basic organic solvent to extract the remaining residue.

The components of the lipstick are now present in solution.
In order to determine the chemical composition of the solutions, they will need to undergo separation and analysis. Three common methods of doing this are:

• thin layer chromatoagraphy (TLC)
• gas chromatography (GC)
• high performance liquid chromatography (HPLC)

Different brands of lipsticks have different chemical compositions so they produce different chromatographs.
Using known brands and colours of lipsticks, the researchers can produce a database of chromatographs. When lipstick evidence is found at the scene of a crime, forensic scientists can produce a chromatogram of it and compare this with the database of known brands and colours in order to find a match. In this way forensic scientists can determine the brand and colour of the lipstick. Law enforcement officials could then investigate whether a suspect uses that particular lipstick.
The researchers are still performing analyses of lipsticks, but at this stage they have reported that the best results are achieved with gas chromatography (GC).

Reference:
American Chemical Society. "Tying lipstick smears from crime scenes to specific brands." ScienceDaily. ScienceDaily, 14 March 2016.

Further Reading:
Percentage composition 
w/w % concentration
Parts per million (ppm) concentration
Lipids (oils, fats and waxes) 
Properties of Carboxylic Acids 
Preparation and Naming of Simple Esters


Suggested Study Questions:

1. A tube of lipstick contains 4.0 grams of lipstick. Calculate the mass of each of the following components of the lipstick:
   
   • castor oil
   • beeswax
   • lanolin
2.  The castor oil used to make the 4.0 grams of lipstick is itself made up of a number of fatty acids notably about 90% ricinoleic acid, 4% oleic acid and 3% linoleic acid. Calculate the mass of each of these fatty acids present in the lipstick.
3. Why do you think the concentrations of chemical compounds found in lipstick are given as % w/w (percentage by weight or percentage by mass) rather than in units of mol L^-1 or ppm?
4.  What is meant by the term "fatty acid" in chemistry?
5.  Draw and name the functional group that is present in both carboxylic acids and fatty acids.
6.  Acetic acid (ethanoic acid) is miscible (soluble in all proportions) in water,  whereas the solubility of pentanoic acid is 3.4 g mL^-1, and of hexanoic acid is 1.0 g mL^-1. Would you expect oleic acid (C₁₇H₃₄O₂) to be soluble in water? Explain your answer.
7.  What is meant by the term "triglyceride" in chemistry?
8.  Draw the functional group that is common to both triglycerides and esters.
9.  Esters are immiscible in water so an organic solvent is used to extract the triglycerides from the lipstick marks. Imagine you have been given samples of cyclohexane, ethanol, and acetone. Which of these do you think would be the best solvent to use on the lipstick mark, and explain your answer.
10.  Design an experiment that you could perform to test your hypothesis in question 9 above regarding which of the solvents would be best to use on the lipstick mark.

HCl as a Primary Standard?

Question: Why is HCl not suitable as a primary standard?
Answer:  There are three main reasons why HCl is not suitable as a primary standard:

• HCl is not a solid at room temperature and pressure. 
• HCl cannot be obtained at a very high purity.
• HCl does not have a high molecular mass.

You can find out more about what makes, and does not make, a primary standard at:
http://www.ausetute.com.au/titrstand.html