Stinky Socks and Shmelly Shirts?

Northumbria University researchers have identified six volatile organic compounds on dirty socks and t-shirts which are responsible for the stench of your dirty laundry. Surprisingly, some of these compounds can survive washing in a machine with detergent at 20°C, that is, washing in cold water will not remove all the compounds responsible for the smell.

The researchers wanted to identify the volatile organic compounds from dirty clothes before washing, after washing while still wet, and after drying, to see which compounds are responsible for bad smells and to see if they were eliminated during the washing process.

6 men and 2 women were each given a new pair of socks. Each person was asked to wash their feet and dry them before wearing the socks for at least 10 hours in a specified type of shoe. Each sock was then placed in a separate bag and stored in the dark overnight. 9 men were each given a t-shirt to wear for 2-3 hours while taking part in a soccer match. After the match the t-shirts were bagged separately and refrigerated.

The researchers smelled each item and graded it on a scale of 0 (no bad smell) to 10 (very bad smell).
Then the items were washed in a Tergotometer, a lab machine made up of several miniature washing machines, at 20°C using non-perfumed detergent. Each item was graded for odour after washing while still wet and then again after drying.

Using analytical techniques like gas chromatography, the team identified 6 main volatile organic compounds that contribute to the smell of dirty laundry:

• butanoic acid (butyric acid); rancid butter odour
• dimethyl disulfide; onion-like odour
• dimethyl trisulfide; powerful, unpleasant odour
• heptan-2-one (2-heptanone); fruity odour like bananas
• nonan-2-one (2-nonanone); herbaceous odour
• octan-2-one (2-octanone); apple-like odour

As the concentration of these volatile organic compounds decreased after each washing, the items became less smelly.


Reference:
Chamila J. Denawaka, Ian A. Fowlis, John R. Dean. Source, impact and removal of malodour from soiled clothing. Journal of Chromatography A, 2016; 1438: 216 DOI:10.1016/j.chroma.2016.02.037

Further Reading:
Scientific Method: http://www.ausetute.com.au/scientificm.html
Experimental Design: http://www.ausetute.com.au/experimentd.html
Writing Lab Reports: http://www.ausetute.com.au/labreport.html
Introduction to Functional Groups: http://www.ausetute.com.au/fungroup.html
Naming Alkanoic Acids: http://www.ausetute.com.au/namalkacid.html
Naming Alkanones: http://www.ausetute.com.au/namalkanone.html
2-Dimensional Structural Formula: http://www.ausetute.com.au/structural2D.html
Condensed Structural Formula: http://www.ausetute.com.au/condensedsf.html
Molecular Formula: http://www.ausetute.com.au/molecularformula.html
Molar Mass Calculations: http://www.ausetute.com.au/moledefs.html
Gas Chromatography (GC) : http://www.ausetute.com.au/gc.html

Suggested Study Questions:

1. What hypothesis was being tested by the researchers in this experiment?
2. Write an aim for the experiment conducted by the researchers.
3. Write a method for this experiment as a series of steps.
4. Tabulate the results of this experiment.
5. Write a suitable conclusion for this experiment.
6. Discuss how you could improve this experiment.
7. Give the 2-dimensional structural formula for each of the following compounds:
• butanoic acid
• heptan-2-one (2-heptanone)
• nonan-2-one (2-nonanone)
• octan-2-one (2-octanone)
8. On each structural formula above, circle the functional group and name it.
9. Classify each of the compounds listed in question 1 on the basis of their functional groups.
10. Give the molecular formula for each of the following compounds:
    • butanoic acid
    • heptan-2-one (2-heptanone)
    • nonan-2-one (2-nonanone)
    • octan-2-one (2-octanone)
11. Give the condensed structural formula for each of the following compounds:
    • butanoic acid
    • heptan-2-one (2-heptanone)
    • nonan-2-one (2-nonanone)
    • octan-2-one (2-octanone)
12. Calculate the molar mass for each of the following compounds:
• butanoic acid
• heptan-2-one (2-heptanone)
• nonan-2-one (2-nonanone)
• octan-2-one (2-octanone)
13. Which of the following do you think would have the longest gas chromatography retention time ? Explain your answer.
    • heptan-2-one (2-heptanone)
    • nonan-2-one (2-nonanone)
    • octan-2-one (2-octanone)
14. Why is gas chromatography (GC) a good choice of analytical technique for this experiment compared to other chromatographic techniques?

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.

HPLC

AUS-e-TUTE has just added new resources for the High Performance Liquid Chromatography (HPLC) topic.
The new resources include a tutorial, game, test and exam.
Go to http://www.ausetute.com.au and log-in to start using these new resources.

The Chemistry Syllabus Study Guides for Queensland, New South Wales, Australian Capital Territory, Victoria, South Australia, and, AP Chemistry (USA and undergraduate) have been updated to include these new resources.

Links to the new resources have also been added from the Class/School Group index page.

Gas Chromatography Resources

AUS-e-TUTE has added new resources for the Gas Chromatography (GC) topic.
You will find links to the new tutorial, game, test and updated exams included in

• Test Centre index page (all members)
• Queensland syllabus study guide for chemistry (Australia)
• New South Wales syllabus study guide for chemistry  (Australia)
• Australian Capital Territory syllabus study guide for chemistry (Australia)
• Victorian syllabus study guide for chemistry (Australia)
• South Australian syllabus study guide for chemistry (Australia)
• AP syllabus study guide for chemistry (USA and undergraduate chemistry)
• Class/School Group index page

http://www.ausetute.com.au

Art Meets Science

Scientists have been using state-of-the-art gas-chromatography-mass-spectroscopy (GC-MS) to study the organic chemistry of old master paintings in the UK National Gallery's collection. GC-MS has been used to study the characterisation and composition of paint binding media, additions to paint media such as resins, and the composition of old varnishes.

Paint binding media include drying oils such as linseed oil, walnut oil and poppy seed oil. Analysis can show whether the oil was pre-treated by heat-bodying, or thickening, before use by the painter. Added resins can be identified and the state of degradation of the binder assessed. Paintings in other media such as egg tempera can be identified, as well as complex combinations of media.

One such painting studied was The Virgin and Child with an Angel, originally attributed to the Renaissance painter-goldsmith Francesco Francia and dated ~1490. The authenticity of the painting was queried in 1954 when another version of the same painting appeared on the market. In 2009, GC-MS was used to test the paint media and varnish, with the conclusion that the painting in the UK collection was a fake painted in the 19th century.

If you happen to be in the UK during July, you can get to see the results of this research for yourself:
http://www.nationalgallery.org.uk/about-us/press-and-media/close-examination

Now, if you happen to be in Australia, you have only a few days left to get yourself to Federation Square in Melbourne to see Rafael Lozano-Hemmer's amazing "Solar Equation" installation. This incredible piece of physics-meets-art is a simulation of the Sun, 100 million times smaller than the real thing, and compresses the entire 11 year solar cycle including solar flares and sunspots into a few short minutes of visual excitement.
http://www.fedsquare.com/index.cfm?pageID=373