A bit about color additives...

Have you ever thought about what ingredients give some cosmetics their bright colors?

 There are many different substances that are used to add color to makeup; some examples include:
            chromium oxide
            mica chips
            dihydroxyacetone
            manganese. 

Color additives are not all made the same way, therefore they are generally classified as one of three different categories:  straight colors, lakes, and mixtures. Straight colors are not mixed with other compounds or subject to any chemical reactions when they are created. Lakes on the other had are formed through chemical reactions involving straight colors, precipitants, and substrata. Mixtures are created by the combination of various color additives without the use of chemical reactions. From these descriptions, it may sound like most color additives used today are synthesized by chemists, not found naturally. There are, however, some color additives that are derived from plants or animals.

This often causes people who are worried about using artificial additives to be reluctant to try these types of products.  Here is a list of FDA approved color additives in addition to the year in which they were approved.

From analyzation of these lists, it was found that certain colors are used for specific reasons.  For example, iron based compounds seem to be have a strong correlation with eye care cosmetics, ie) contact lenses.

Not only can you find color additives in make-up products but also in hair products like hair dyes.  Though there is the side of an initial strong odor in the hair dyes, leaving the product in for too long, can cause irritation and rashes.  For that reason, it is advised that the product is only in for a maximum of 30 minutes.



Can you guess which compound produces which pigment?
(answers will be posted along with our next blog post, all about the kinetics and rate of making cosmetics!)

Let's Make Some Soap!

Most of us (or at least I hope) have used soap since birth, but we haven't really wondered how it works and what it is made of. We will delve deeper into the formulation of soap in this blog post:

Hydrolysis of these fats and oils yields glycerol and crude soap.

Saponification is the fancy schmancy term for making soap. It comes from the Greek root sapo- which means soap. "Basic"ally, it is the chemical reaction between an acid and a base to form a salt. You need to mix an oil, or a fat (which is your acid) with Lye, which is the soapmaker's term for sodium hydroxide, a base. This forms soap, which is a salt.

So how does the mixing of these two different things combine to form something like soap. In order to understand this, you must consider the chemical makeup of the acid and base being used in the reaction.

The base can vary, but it has to have one hydroxide ion. Lye, which as stated above is sodium hydroxide, is often used, but other bases such as potassium hydroxide can be used as well. Potassium hydroxide is more commonly used in liquid soaps, because it is more soluble than sodium hydroxide.

There are also many different types of acids that will react with your base to "saponify". It could be olive oil, coconut oil, or tallow, which is animal fat. These may not seem like the type of acids you might be used to (HCl, HNO3, etc.), but these are all "fatty acids", which is a carboxylic acid group with a long hydrocarbon tail. The carbon tail gives the soap its hydrophobic qualities.

Arachidic acid, with a carboxylic acid group on the right and a 20 carbon tail

Each acid has a unique combination of triglycerides (a compound made of three fatty acid tails attached to a single molecule of glycerol), which combines with the base differently. The fatty acid tails join with the base to make soap, and glycerol is leftover. This glycerol molecule keeps the soap moist.

The OH group from the base makes the soap hydrophilic, and the fatty acid tail makes the soap hydrophobic, thus overall, the soap molecule is amphiphilic. This amphiphilic property is essential in soaps, because the hydrocarbon tail will mix with the oil and grease on your hands, while the ionic end mixes with the water. This allows all the gross stuff on your hand to be pulled away by water, where normally, it would have just repelled the water.

bar soap is typically made from NaOH

Now you know about the soap making process, time to get your hands dirty and make your own!

Here is a recipe taken from Nuffield Foundation's Practical Chemistry

MAKING SOAP:

Making soap
a Place about 2 cm³ of castor oil in a 100 cm³ beaker using a dropping pipette, followed by 5 cm³ of ethanol. Stir with a glass rod to mix.

b Add 10 cm³ of sodium hydroxide solution..

c Prepare a waterbath containing near-boiling water from an electric kettle so that you can safely lower the small beaker into it without spillage. A 250 cm³ beaker may be used as the waterbath. Do not use too much water, as the small beaker needs to be supported without risk of the water coming over the top.

d Stir the mixture in the beaker with a glass rod for 5 minutes. If the water bath cools too much, you may need to renew with fresh boiling water.

e Meanwhile in a boiling tube make a saturated solution of sodium chloride by shaking solid sodium chloride with 10 cm³ of water until no more will dissolve. Allow to settle.

f After 5 minutes, add the saturated sodium chloride solution to the small beaker and stir.

g Cool the mixture by changing to a cold water bath (or an ice bath if available).

h Soft, white lumps of the soap will gradually form in the mixture. Leave for a few minutes to improve the yield. During this time the soap may rise to the surface and form a soft crust on cooling.

i Using a pump, with a fresh filter paper damped down in the funnel, filter off the soap, breaking up the crust with a glass rod if necessary

j Allow the soap to drain on a paper towel – do not touch it with your fingers, as it may still contain sodium hydroxide.

k Use a spatula to transfer a little of the soap to a test-tube, and add a few cm³ of purified water. Shake well! What happens? You have made a soap!

cups of homemade soap! The color comes from melted crayons

jennymu

Nanoparticles, What Else Are They Good For?

Faithful blog visitors, you'll remember that we have previously dedicated a blog post to nanoparticles and the world of cosmetics dealing with anti-aging products. But perhaps some of you have taken umbrage at our vanity, and so to appease you, we will speak today about nanoparticles and their role in antibacterial products (at which only the unhygienic may take umbrage).
Silver has always been known for its antibacterial properties. The Ancient Phoenicians knew to keep water, wine, and vinegar in silver vessels to ensure freshness. Now in our modern age we have harnessed the technology to understand silver's antimicrobial properties and to repackage it into an even more efficient antibacterial agent. As it turns out, silver disrupts the bacteria's ability to form chemical bonds essential to its survival. Such bonds are the reason for the bacteria's physical structure, so when they meet the silver, they fall apart. How, though, can we make this process even more efficient?
Nanoparticles.
Scientists have irradiated silver nitrate solutions with electron beam technology to release silver ions that then group together to form the nanoparticles in use.

Silver ion nanoparticles 

This is optimal for two reasons: cost and control. Irradiation to produce nanoparticles has proven more cost-effective than using hazardous reducing agents and this can be adjusted to produce nanoparticles of a particular size, controlling their properties. If you've been paying attention to the news recently, you will know that bacterial resistance to conventional antibiotics is a growing concern for the medical community. This is why the nifty new technology of nanoparticles has been flourishing over the past couple years. And preliminary tests already show promising results. Silver nanoparticles are a straightforward, nontoxic method active against such bacteria as Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, common disease-causing bacteria.

S. Aureus

E. Coli

P. Aeruginosa

If we may reveal our vain face once again, silver nanoparticles are particularly appreciated by burn victims. Antimicrobial gels using silver nanoparticles have been heralded as the best new thing, proving more efficacious than its brothers (other drugs using silver ions in their technology) in its antibacterial effects and to reduce scarring. As a result, many drugs have already been green-lighted to utilize this technology.

Elta - one of the many antimicrobial wound gels using silver nanoparticles 

As we move into the future, it seems more and more is being discovered about the benefits of nanotechnology. We have seen how it may be used to fight wrinkles but not we are seeing how it is essential to the fight against bacteria which seem to be fighting back with equal force against conventional methods. Nanoparticles are the key to the future of antibiotics. 

References:
http://www.ncbi.nlm.nih.gov/pubmed/19473014
http://www.sciencedaily.com/releases/2010/05/100524101339.htm
http://www.silverinstitute.org/site/silver-in-technology/silver-in-medicine/bandages/

andrew

Lets Mix Oil and Water Part 2: Thermodynamics

Emulsions are so fun we had to split it into two blog posts!
This post will focus and go more in depth on emulsions, particularly the thermodynamics of making emulsions:

Emulsions can be considered from a thermodynamic standpoint as well.
They are considered metastable - i.e. the emulsion has a thermodynamic drive to return to the state of lowest energy. The only point in time where an emulsion is completely stable is when it is separated. Thus, mixing two liquids will have a thermodynamic effect.

If two liquids are completely compatible, they do not form an interface, which is the surface between two different phases. In this case, the free energy of mixing is negative, because the two compatible liquids want to be together, and release energy when they mix.
However, if two incompatible components are mixed, they do form an interface, and the free energy of formation is positive because these two liquids do not want to be near each other, and thus require energy to be mixed together. As in the previous blog post, you saw how emulsifiers cause small micelles, or little balls of oil to form in the water.

Micelles are small droplets surrounded by an emulsifier suspended in liquid

This causes an increase in interfaces, because now each droplet has its own interface surrounding it, as opposed to before, when the separate layers only had a single interface between the two. The increase in interface causes more interactions between two substances that don't want to be together, and so clearly the energy and thermodynamics will be affected.

In order to get an idea about the thermodynamics of an emulsion, we can look at the Gibbs free energy of the system, which, as we learned in class, is the supreme equation of all of life, and is represented by the following equation:

The entropy (∆S) is a measure of the extent of disorder in the system and in the mixing of two liquids measures the size reduction of the droplets (or increase in the number of droplets). During the formation of an emulsion, we want to increase the number of droplets, and make each droplet smaller, and so ∆S is going to be positive.
∆H is the enthalpy of the system, and can basically be considered the energy input needed to achieve a certain average droplet size, and can be expressed by γ∆A, where γ is the tension of the interface, ∆A is the change in area of the interface, T is the temperature, and ΔS is the entropy of mixing.
Therefore, the thermodynamics of emulsions can be expressed as a derivation of the Gibbs free energy equation:

ΔG = (γ∆A) – (TΔS)


ΔG gives us information about the stability of the emulsion. If ∆G is positive, then energy is required, and so spontaneous emulsification is highly unlikely, similar to a ball spontaneously rolling back up a hill. If ∆G is negative, however, then spontaneous emulsification will occur. This happens with two liquids that are miscible, and will readily mix.
As stated above, if two incompatible components, like oil and water, are mixed, an interface is formed, and the ∆G is positive, so it will always be non-spontaneous, i.e. no matter how long you leave a bottle of salad dressing on the counter, the oil and water will never magically mix. However, the closer ∆G is to zero, the easier the emulsification process.

The oil and water here will never mix unless you add some energy to the system

Let's try to better explain ∆G and emulsion formation with some fun diagrams!


Free energy of emulsion formation (between components 1 and 2)


In general, γ∆A >> T∆S


and so ∆G >> 0


the formation of an emulsion requires energy








Free energy of emulsion breakdown





∆Gbreak << 0
(if ∆Gform >> 0)



Breakdown is spontaneous






Considering the thermodynamics of emulsions is important because it can help cosmetic companies figure out how their lotions and creams will react over time. Because breakdown of an emulsion is spontaneous, ultimately, all lotions and creams will separate into their separate components, but the addition of emulsifiers can slow this process down, or make it easier to evenly mix the oil and liquid by lowering ∆G.

Watch out! That lotion you're using is thermodynamically unstable, and will break down into its oil and water components eventually

jennymu

Lets Mix Oil and Water

Happy New Year faithful readers!
Let's bring in 2013 with more about the chemistry behind cosmetics.
Expect more posts in the coming year with more of an emphasis on the chemistry that takes place in manufacturing of cosmetics. :)

Today we're going to talk about emulsions:

Listen to this helpful podcast from BASF "The Chemical Reporter" to get some background information on emulsifiers

Emulsifiers, or surfactants are molecules that have special properties. They contain two parts: one that can dissolve in water (the hydrophilic end) and one that can dissolve in oil (the hydrophobic end). You will see this structure again in our upcoming blogpost on soaps and saponification, so keep it in mind.

Basic structure of an emulsifier

Emulsifiers are used to reduce the tendency of oil and water to separate into layers by forming an emulsion. An emulsion is formed when tiny droplets, called micelles, of one liquid are suspended in a another liquid.
Emulsifiers change the surface properties of liquids. The hydrophobic tail of these molecules burrows into the oil, leaving the exposed hydrophilic head out to bind to water molecules. When the oil and water mixture is agitated, micelles will form.

What do emulsions look like?

Emulsions usually have a cloudy appearance, because of all the different phase interfaces, which are the layers between two different phases, and in this case, the two different immiscible liquids. When you just have oil and water in a cup, the oil and water form two separate layers, with one interface, between them. However, when you add an emulsifier, and mix them together, small micelles will form with interfaces around each micelle. All these interfaces scatter light as it passes through the emulsion, giving it a cloudy appearance.

Emulsions appear white when all light is scattered equally, but if an emulsion is dilute enough, there are less micelles in solution and shorter wavelength light will be scattered more, making the emulsion appear more blue. If the emulsion is concentrated enough, longer wavelengths will scatter more, and the emulsion will be yellower. An example of this would be skimmed milk, compared to creams. Speaking of creams, comparing the creams that are used for skincare to just lotion (provided there is no artificial coloring) will also demonstrate this effect.

But why are emulsions important in cosmetic chemistry?

The majority of Skin Care products and a very significant percentage of toiletry products are emulsions. The basic components of these formulations are emulsifiers, emollients, and consistency enhancers. The chosen emulsifier for a product is not only crucial for the stability of an emulsion (and thus the preventing of separation, which no one wants), but also has a large impact on consistency, skin feel, and care properties of a formulation. Emulsifiers have a wide range of applications in cosmetic products. They are used in creams, lotions, sprays, and foams.

For the purposes of this blog post, we will be focusing on the emulsions of creams and lotions, and leave sprays and foams for another blog post.

Here is a helpful table of common emulsifiers used in cosmetic products:

What we've talked about so far is nice, but lets delve deeper, and look at the thermodynamics of emulsions. Stay posted for the second part of the blog post, to be published on January 11th

jennymu