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.

Arsenic Tests

Somewhere around the 8th century, an Arab alchemist produced white arsenic trioxide (As₂O₃) from realgar, a naturally occurring arsenic sulfide mineral, As₄S₄:
As₄S₄ + 7O₂ → 2As₂O₃ + 4SO₂ Arsenic trioxide became one of the most widely administered poisons in history, and therefore, it became necessary to find reliable tests to show whether or not arsenic was present in a sample of food or drink, or whether it was present in a corpse.

In 1775, Carl Wilhelm Scheele treated arsenic trioxide with nitric acid and zinc which resulted in arsine gas (AsH₃), zinc nitrate and water:
As₂O₃ + 6Zn + 12HNO₃ → 2AsH₃ + 6Zn(NO₃)₂ + 3H₂O Arsenic was said to be present if an odour of garlic was produced because arsine gas smells a lot like garlic.

In 1787, Johann Metzger used a carbon reduction method to produce carbon dioxide gas and solid arsenic from arsenic trioxide and carbon:
2 As₂O₃ + 3 C → 3 CO₂ + 4 As As the arsenic trioxide is heated with charcoal, an "arsenic mirror" forms on the charcoal.

In 1785, Samuel Hahnemann produced a bright yellow precipitate of arsenic trisulfide, As₂S₃, by passing a stream of hydrogen sulfide gas, H₂S, through an acidified arsenic solution.

In 1836, James Marsh designed an apparatus that would detect and measure arsenic.
The sample is placed in a flask with arsenic-free zinc and sulfuric acid.
Arsine gas forms:

As₂O₃ + 6 Zn + 6 H₂SO₄ → 2 AsH₃ + 6 ZnSO₄ + 3 H₂O

The arsine gas is fed through a drying tube to a glass tube which is heated.
Arsine deomposes on heating, forming elemental arsenic which is a shiny black substance:

2 AsH₃ → 3 H₂ + 2 As

By placing a cold surface at the end of the heated tube it is possible to condense this arsenic, which forms a black "mirror".

http://www.youtube.com/watch?v=-vUZdAwgl2g

Today, these "wet" methods of chemical detection have been superceded by instrumental analysis. e Atomic absorption spectroscopy (AAS)  can now be used to determine not only the presence of arsenic, but also how much arsenic is present.

Further Reading:
Solubility Rules
Writing Precipitation Equations
Gravimetric Analysis
AAS
Oxidation and Reduction 
Carbon Reduction Methods

Suggested Study Questions:

1. Give the oxidation state (number) for arsenic in each of the following:
   • As₂O₃
   • As₄S₄
   •  AsH₃
   • As
2. For the reaction: As₄S₄ + 7O₂ → 2As₂O₃ + 4SO₂ which element, or elements, have been oxidized?
3.  Consider the reaction: 2 As₂O₃ + 3 C → 3 CO₂ + 4 As
   Is arsenic likely to be more or less active than carbon?
4. Write a possible net ionic equation for the reaction in which arsenic ions react with  hydrogen sulfide gas to produce a precipitate of arsenic trisulfide.
5. Consider the reaction: 2 AsH₃ → 3 H₂ + 2 As which results in the formation of a shiny black "mirror" of arsenic.
   • Has arsenic been oxidized or reduced?
   • Has hydrogen been oxidized or reduced?
   • If 1 mole of arsine gas decomposes completely, how many moles of hydrogen gas would be produced?
   • At 0^oC and 100 kPa, what volume of gas would be produced by the thermal decomposition of 25 moles of arsine?
   •  At 0^oC and 100 kPa, what mass of arsenic would be deposited after  the thermal decomposition of 150 mg of arsine.
   • At 25^oC and 100 kPa, what mass of arsine will decompose to produce 0.05 L of hydrogen gas?
   • A sample of gas containing arsine produces an "arsenic mirror" containing 0.02 g of arsenic. What mass of arsine was present in the gas sample?

Bone Composition

Bone is a kind of specialized connective tissue providing a supportive framework for the body. Bones are continually being remodeled during the life of the body so they can be used to determine the age of a body.

About 70% of bone is made up of calcium hydroxyapatite, 3Ca₃(PO₄)₂.Ca(OH)₂.
The crystals of calcium hydroxyapatite in bone are very small, about 5nm x 5 nm x 40nm.
The total surface area of calcium hydroxyapatite in bone is extremely large, about 40 hectares in the skeleton of a 70kg man.
About 10% of bone is made up of water, and the other 20% is made up of organic compounds such as collagen. The term collagen refers to a group of proteins, and is the most abundant protein found in mammals, about 30% of all the protein in the body is collagen.

The bone of very young people, less than 4 years of age, is called woven bone because the collagen fibres are interwoven and run in all directions just like a piece of felt, and the bone contains large holes like Swiss cheese.

The bones of bones of adults include lamellar bone which has collagen fibres organized into layers or sheets known as lamellae. These are usually built up around blood vessels like the layers of an onion. This produces compact bone.
Adult bones also include trabecular (cancellous, spongy) bone. The bone itself is in the form of little beams (trabeculae) which are about 200μm thick. The spaces in the bone can contain marrow.

Osteoporosis refers to a decrease in the amount of bone tissue which results in an increased tendency for the bone to fracture. The shape and size of the bone doesn't change, but the little beams, the trabeculae, become thinner and some may disappear altogether.
Astronauts in space can also display a decrease in the amount of bone tissue because there is less load, and therefore less stress, on their bones in space.

Aerobic and resistance training increase the density. Bone is deposited when there is load, and stress, applied to the bone.

Scientists at the Rensselaer Polytechnic Institute have developed a new technique to analyze the bone matrix. This technique provides information about the concentration of different proteins in the bones, which can be used to determine how the bone was formed, how it has been modified over time, and, if the bone is prone to fracture.

Reference
G. E. Sroga, L. Karim, W. Colon, D. Vashishth. Biochemical characterization of major bone-matrix proteins using nanoscale-size bone samples and proteomics methodology. Molecular & Cellular Proteomics, 2011; DOI: 10.1074/mcp.M110.006718

Further Reading
Molecular Mass (Formula Weight)
Percentage Composition
Unit Conversions
Density
Mass-Mole Calculations

Study Questions

1. Calculate the molecular mass (formula weight) of calcium hydroxyapatite.
2. Calculate the percentage composition of calcium hydroxyapatite.
3. 1 hectare is 1,000m², what is the surface area in m² of calcium hydroxyapatite crystals in a 70kg man?
4. If you laid out all the calcium hydroxyapatite crystals in the bones of the 70kg man above onto a football field, how many football fields would you need? (Assume a football field is about 6,000m²)
5. The little beams in trabecular bone are 200μm thick. Convert this to a thickness in
   
   • meters
   • millimeters
   • nanometers
   • angstroms
6. The density of a bone in the leg is about 2g/cm³. 70% of bone is made up of calcium hydroxyapatite. Calculate:
   • the mass of calcium hydroxyapatite present in a 500cm³ bone sample
   • the moles of calcium hydroxyapatite present in the same bone sample
   • the percentage of calcium present in the same bone sample
   • the mass of calcium present in the same bone sample
   • the mass of water present in the same bone sample
   • the mass of organic compounds present in the same bone sample
     
7. Which type of bone, woven bone or lamellar bone, has the greatest density? Explain your answer.
8. Will the bones of a person suffering from osteoporosis be more or less dense than the bones of an athletic young adult? Explain your answer.
   
   

Fingerprint Powders

University of Queensland scientists have just completed a study revealing that the human factor involved in the process of identifying a set of fingerprints could lead to errors and false convictions of innocent people.
In the study 37 qualified fingerprint experts and 37 novices were given pairs of fingerprints to examine and decide whether a simulated crime scene matched a potential suspect or not. Some of the print pairs belonged to the "criminal" while others were highly similar but actually belonged to an "innocent" person.
The experts correctly matched just over 92 percent of the prints to the criminal. But, they mistakenly matched 0.68 percent of the prints to the innocent person.

Fingerprint powders are fine powders used in dusting for fingerprints by crime scene investigators. Fingerprint powders are often white or black in colour. White powders would be used on dark surfaces while black powders would be used on light coloured surfaces.

Examples of powders that have been used to dust for fingerprints:

White Powders Black Powders Calcium oxide Chalk Titanium dioxide White tempera (starch + titanium dioxide) Haddonite white (titanium dioxide + kaolin + chalk) Lanconide (zinc sulfide + zinc oxide + barium sulfate + titanium dioxide + bismuth oxychloride + calcium carbonate) Charcoal Graphite Lampblack Dragon's blood (Daemonorops draco plant resin) Haddonite black (lampblack + graphite + powdered acacia) Dactyl black (graphite + lampblack + gum acacia)

The fingerprint powder must be fine enough to show fingerprint details. The finer the powder is the better it should be.
To be a good fingerprint powder the powder must adhere to, or stick to, the fingerprint but not to the surface the fingerprint is on.


Reference:
Association for Psychological Science (2011, May 11). Dusting for fingerprints -- It ain't CSI. ScienceDaily. Retrieved May 15, 2011, from http://www.sciencedaily.com­ /releases/2011/05/110511162536.htm

Further Reading:
Pure Substances and Mixtures
Elements and Compounds
Allotropes
Writing Ionic Formula
Calculating Percentage Composition

Study Questions

1. What are the main chemical constituents of:
   
   • chalk
   • lampblack
   • charcoal
   • graphite
2. Draw up a table dividing the fingerprint powders into pure substances and mixtures.
3. For the pure substances listed in question 2, draw up another table dividing these up into elements and compounds.
   
4. Write the chemical formula for each of the following:
   
   • calcium oxide
   • titanium dioxide
   • zinc sulfide
   • zinc oxide
   • barium sulfate
   • calcium carbonate
5. Calculate the percentage composition of each of the following compounds:
   • calcium oxide
   • titanium dioxide
   • zinc sulfide
   • zinc oxide
   • barium sulfate
   • calcium carbonate
6. Titanium dioxide features in many of the recipes for making white fingerprint powders. What properties of titanium dioxide make it useful for this purpose?
7. Graphite is a common constituent in many black fingerprint powders. What properties of graphite might make it particularly useful as a fingerprint powder?
8. For the University of Queensland study, give examples of the following types of variables:
   
   • independent variable
   • dependent variable
   • controlled variables
9. Based on the information provided in the article, do you think the University of Queensland study was a fair test? Explain your answer.
10. Design an experiment to test the statement that graphite is a better powder than charcoal to use for detecting fingerprints on the surface of tiles.
    
    

VMD for Fingerprinting

Forensic experts at the University of Abertay Dundee and the Scottish Police Services Authority (SPSA) are researching vacuum metal deposition (VMD) to recover fingerprint ridge detail and impressions from fabrics.

Vacuum metal deposition, VMD, is a common method of depositing a thin film on a substrate.
The source metal is evaporated in a vacuum which allows the vapor particles to travel directly to the target object, the substrate, where they condense back to the solid state. Evaporated materials deposit non-uniformly if the substrate has a rough surface, and, because the evaporated material attacks the substrate mostly from one direction, protruding features block the evaporated material from some areas which is called "shadowing" or " step coverage".

The Scottish scientists have been using gold and zinc in a VMD process to recover fingerprint marks on fabrics. The fabrics are placed in a vacuum chamber then gold is heated up to evaporate it. The gold particles spread out in a thin film over the fabric. Zinc is then heated up, and the zinc particles attach to the gold particles where there are no fingerprint residues. The fingerprint ridges show up as clear fabric, but where there are no fingerprint ridges the distinctive grey colour of the zinc metal is seen.

While only 20% of the public are classed as "good donors" for leaving fingerprints, the researchers have had great success in revealing the shape of a handprint on a number of fabric types. Handprints could help the police piece together a timeline of events which could be used to provide evidence in cases where someone was pushed, or grabbed, in a particular area of their clothing. For example, an impression of a palm print on the back of someone's shirt might indicate they were pushed off a balcony, rather than jumping.

Reference
Joanna Fraser, Keith Sturrock, Paul Deacon, Stephen Bleay, David H. Bremner. Visualisation of fingermarks and grab impressions on fabrics. Part 1: Gold/zinc vacuum metal deposition. Forensic Science International, 2010; DOI: 10.1016/j.forsciint.2010.11.003

Further Reading
Physical and Chemical Changes

Study Questions

1. What do Chemists mean when they refer to evaporation?
2. What do Chemists mean when they refer to condensation?
3. Are evaporation and condensation examples of chemical or physical changes? Explain your answer.
   
4. Write a chemical equation to represent the evaporation of solid gold as described above in the process of vacuum metal deposition.
5. Do you think the equation you wrote above is an example of an evaporation process? Explain your answer.
6. Write a chemical equation to describe the process of gold vapor condensing on a fabric as described in the process of vacuum metal deposition.
7. Give the name for the change of state being described in each of the following:
   
   • heating solid gold until it forms a liquid
   • heating solid gold in a vacuum so that it forms a vapor
   • cooling gold vapor in a vacuum so that if forms solid gold
   • cooling gold liquid until it forms solid gold
   • heating liquid gold until it forms gold vapor
   • cooling gold vapor until it forms liquid gold
     

Luminol - Detecting Blood

Luminol is a common reagent used to detect blood stains and other body fluids at crime scenes because it reacts with iron in blood to produce a blue glow.
Its IUPAC name is 5-amino-2,3-dihydro-1,4-phthalazinedione.

The luminol solution used by crime scene investigators is a solution of luminol and an activator, an oxidant such as hydrogen peroxide and a hydroxide salt in water. In the presence of a catalyst, such as the iron in haemoglobin, the hydrogen peroxide decomposes to form oxygen and water and the luminol reacts with the hydroxide salt to form a dianion. The oxygen produced during the decomposition reaction reacts with luminol dianion producing an organic peroxide which is very unstable and immediately decomposes to produce 3-aminophthalic acid with electrons in the excited state. As the excited state electrons relax to the ground state, energy is released as visible blue light.

Unfortunately, luminol reacts with other substances besides the iron in haemoglobin such as copper, bleaches and horseradish.

University of South Carolina Chemists are using a new thermal infrared technology to illuminate blood stained objects with pulses of invisible infrared waves, using filters to block out particular wavelengths, allowing certain chemicals to stand out from their surroundings. The technique can detect blood diluted to as little as one part blood in 100 parts water. It can also distinguish between blood, bleach, rust and coffee.

Journal References:

1. Heather Brooke, Megan R. Baranowski, Jessica N. McCutcheon, Stephen L. Morgan, Michael L. Myrick. Multimode Imaging in the Thermal Infrared for Chemical Contrast Enhancement. Part 3: Visualizing Blood on Fabrics. Analytical Chemistry, 2010; 82 (20): 8427 DOI: 10.1021/ac101107v
2. Heather Brooke, Megan R. Baranowski, Jessica N. McCutcheon, Stephen L. Morgan, Michael L. Myrick. Multimode Imaging in the Thermal Infrared for Chemical Contrast Enhancement. Part 2: Simulation Driven Design. Analytical Chemistry, 2010; 82 (20): 8421 DOI: 10.1021/ac101108z
3. Heather Brooke, Megan R. Baranowski, Jessica N. McCutcheon, Stephen L. Morgan, Michael L. Myrick. Multimode Imaging in the Thermal Infrared for Chemical Contrast Enhancement. Part 1: Methodology. Analytical Chemistry, 2010; 82 (20): 8412 DOI: 10.1021/ac101109w

Further Reading
Functional Groups
Molecular Mass (Formula Weight)
Percent Composition (percentage composition)
Oxidation and Reduction
Energy Profiles and Catalysts
Parts per million concentration

Study Questions

1. Write the molecular formula for luminol given the structural formula shown in the article above.
2. Calculate the molecular mass (formula weight) of luminol.
3. Calculate the percentage of each element present in luminol.
4. Write a balanced chemical equation for the decomposition of hydrogen peroxide as described in the article.
5. The new thermal infrared technique can detect 1 part blood in 100 parts of water. Express this as a concentration in parts per million.
6. On the structure of luminol locate the following functional groups:
   • amine groups
   • double bond
   • carbonyl group
7. Luminol reacts with the hydroxide salt to form a dianion. Explain what is meant by the term dianion.
   
8. Explain how luminol could produce a dianion.
9. Do you think that crime scene investigators should use luminol to detect blood in commercial laundry? Explain your answer.
   
   

Grave Detection Techniques

Cadaver-sniffing dogs or ground penetrating radar are used to detect clandestine gravesites, but, these are not always useful if the body is buried under concrete.
Scientists at the National Institute of Standards and Technology (NIST) have developed a technique that can reliably detect biochemical changes in a decomposing cadaver.
The process uses an alumina-coated porous layer, open tubular (PLOT) column with a motorized pipette that pulls in air samples at ambient temperatures. The device detects trace amounts of ninhydrin-reactive nitrogen (NRN) that collects in air pockets above and close to grave-soil. The probe, slightly thicker than a human hair, can be inserted into the ground to detect decaying flesh.

Reference:
Tara M. Lovestead, Thomas J. Bruno. Detecting gravesoil with headspace analysis with adsorption on short porous layer open tubular (PLOT) columns. Forensic Science International, 2010; DOI: 10.1016/j.forsciint.2010.05.024

Study Questions

1. What is meant by the term ambient temperature?
2. What is the other major use for ninhydrin in forensic science?
3. Could this probe be used to distinguish between a human cadaver and a dead, decaying rat? Explain your answer.
4. Why do you think cadaver-sniffing dogs might not be useful if a body is buried under concrete?
5. Imagine you have been asked to set up an experiment to determine the effectiveness of this technique at different stages of decomposition. Describe how you would do this.
   

MALDI-MSI and Fingerprints

A fingerprint is made up of material from the surface of the skin and from gland secretions, which can be detected and analysed. Fingerprints found at a crime scene are often lifted using a powder, and compared with prints on a database to identify a suspect.

Matrix-Assisted Laser Desorption/Ionisation Mass Spectrometry Imaging (MALDI-MSI) is usually used to map different molecules within tissue sections, but, scientists at Sheffield Hallam University have just used the technique to analyse and produce images of fingerprints. Fingerprints analysed this way provided a wider range of information, eg, the technique can detect the presence of drugs and medication, and can provide information about a person's diet.

Reference:
Rosalind Wolstenholme, Robert Bradshaw, Malcolm R. Clench, Simona Francese. Study of latent fingermarks by matrix-assisted laser desorption/ionisation mass spectrometry imaging of endogenous lipids. Rapid Communications in Mass Spectrometry, 2009; 23 (19): 3031 DOI: 10.1002/rcm.4218