Friday, 28 December 2012

Plastic not so Fantastic: Water Bottle, Plasticizers and Surface Tension

I was in the lab yesterday and wanted to compare the surface tension of water from our MilliQ system and water that is in these plastic bottles.  I used the Kibron EZ-Pi Plus in static surface tension mode.  The surface tension of water is 72.8 mN/m.  This was the value from the MilliQ water.  However, when I did the same test with the plastic from the water bottle it lowered the surface tension to 71.0 mN/m.  These water bottles and other materials like a silicone septum may contain plasticizers, silicone or other surface active materials.  This leaching of these chemicals may cause false positives or add confusing results to when measuring surface active substances from drugs to lipid molecules.  Particular precautions should be made in order to limit the leaching from these bottles (eg. working with glass or ceramic, degassing water, working with the water touching the plastic within a small time period). 

Even if you do not work in a lab or care about surface active substances this result can still affect you.   You likely at some point have had a drink from a plastic water bottle at some point in your life.  Sure it has a nice little sticker printed on the front of it.  It says the it pours from some glacier you have never heard about.  It could also come from a local well that is said to be a fountain of youth.  It has a sealed cap.  It must be good stuff.  Anything that is branded has a name and is in my local market must be good.  Right? 

Wrong.  Even if the water is said to be pure, a plastic container may leach chemicals such as phthalates or bisphenol A (an industrial chemical linked to increased risk of birth defects, miscarriage, baldness and prostate cancer) into the bottled water. Scratches in the plastic, harsh detergents, and boiling liquids exacerbate the leaching. 

However,  tap water is probably better which in the end you are just buying in bottled form.  In the end some say that up to 40% of bottled water is tap water.  In addition some brands contain chemical contaminants at levels above strict state limits. If consumed over a long period of time, some of these contaminants could cause serious health problems.

What is the best water bottle to drink from?  For personal health, the ideal water container is glass. However, glass bottles are rare, heavy, and breakable. Many believe polycarbonate (PC) plastic is a good option due to its durability and lack of odor, but it can still leach bisphenol A into its contents and with a recycling code of number 7, is rarely recyclable. A better health option may be one of the new bio-based alternative plastics (such as those made with corn starch)—not really a plastic, but with similar properties, yet reusable and readily biodegradable.

If you can’t avoid drinking water from plastic bottles, make certain it has not been exposed to high temperatures, such as being left inside a locked up car or near a glass window. 0.001 ug/L with LC/MS.  However some of the degraded BPA may be present as well which might be just as harmful.  To find the total organic carbon.  Measuring surface tension will allow you to see if there are any of these leached substances quickly and easily. 


Tuesday, 18 December 2012

Oil Christmas Trees in Texas

Surface tension and other natural physical phenomenons has become a central way to make interesting artistic projects.  Ferrofluids, electromagnetism and surface tension create interesting art together.  Ferrofluids are oil laces with bits of iron oxide.  The iron allows this fluid to become magnetic when a magnetic field is applied.  Japanese artist Sachko Kodama turned her ferrofluid creation into a Christmas special that the people at Exxon or BP must love.  She probably noticed the effect of surface tension when she applied the field and realized there are branches like that of a Christmas Tree.  The surface tension of the oil causes the branches to pull into themselves forming sharp tips.  There is a spiral effect from the two towers which spray fluid out allows these Christmas trees to seem to blossom.

Maybe she is is trying to tell us something?  A relationship between oil and the life blood of Christmas or that humans do not value living things anymore but oil is more important.  Or maybe she just saw a cool effect with surface tension and electromagnetism to show through art.

Check out her site she has some really cool stuff using ferrofluids and other physical properties.

Monday, 10 December 2012

Shake it, shake, shake, shake it: Getting from wet to dry

We are all limited by the physics around us so we have to adapt in order to get things done.  In this case the getting thing done is getting water off of your body.  If left on the body water can collect dust, form mildew, provide unwanted heat exchange among other things.  So it is essential for mammals to get dry.  Water has a defined surface tension and density whereas your skin and hair on your body might change.  The gravity does not change unless you are in space (so maybe getting dry in space is not such a big deal). 

So how do mammals with hair get dry?  This was the question researchers asked.  And more interesting:  What frequencies are needed for a dog and other animals to shake water from their body?

The conclusion?  In order for a small animal (like a mouse) to get dry it needs to shake faster (30 Hz) whereas an animal like a dog the size of a Labrador (4 Hz) or larger say a Panda bear would need far less shaking in order to get the dermal tissue dry enough.  Loose skin also factors into the equation.  If an animal as small as mouse shakes like a Panda he would not get dry.

via io9

Thursday, 6 December 2012

Crazy DNA Remembers its Shape

Just add water and this DNA hydrogel forms into the letters DNA.  The texture reminds me a little bit of those little toy dinosaurs that you put into the water and they grow into bigger dinosaurs.  But hydrogel is not so much different than the superabsorbant polymer in that both are polymers and a hydrogel can contain up to 99.9% water (much less for the larger dinosaur).  
People are doing a lot of different research on hydrogels and have found many applications including: biosensors, environmentally sensitive smart gels, tissue engineering, contact lenses, drug delivery (put some drugs in a hydrogel that slowly releases them over time), water gel explosives and rectal drug delivery.  Some other less common uses are breast implants and adhesives.  Scientists are trying to get the right physicochemical characteristics like rheology, viscoscity, and surface tension to help make new applications.  
What makes this hydrogel different?  Firstly, it is made using DNA.  DNA  make different shapes during replication and branching.  Understanding  branched DNA has led to making new shapes with  DNA, termed DNA origami.  This new molecular scale engineering have also helped scientists make new drug delivery vehicles e.g. putting drugs in a box constructed by DNA.  This hydrogel is not so different than the DNA origami except that it reacts to make the shapes with water.
This was reported in Nature Nanotechnology.  We'll see if these scientists can take it to the next level to produce better drug delivery vehicles and perhaps better wound treatments with water absorbing hydrogels.  Possibly the art community might also contribute to make interesting shape shifting hydrogels but hopefully not by making DNA dinosaurs.  

Tuesday, 4 December 2012

Icy Business: The Surfactants Behind Hockey Ice

In Helsinki it is really cold.  I believe yesterday was -15 C.  It was snowing, there was ice and now there is more ice.  Kids have their skates and are playing hockey outside.  My colleague mentioned that he made some ice the other day for his complex.  It sounds like a stupid question but I asked anyway.

'How do you make ice?'
'Well you take water and put it out on the surface.  We have a pump out back with a hose.'
'And then you wait for it to freeze. Then you add more water and using a sharp tool you level it.'

I have never made ice but likely the ice that is homemade does not look nor feel anything like you would get in an NHL game. Since I have never made ice I take it for granted the great looking ice at the ice skating rinks and hockey arenas.  There is a lot of work to make ice from the ice makers to the zamboni drivers to clean it as well as some surface chemistry that I was not aware.

Canadians are actually some of the best ice makers as they have made the ice at a number of the winter Olympics (and putting a Loony in the center ice for good luck). They have also created products for making better ice surfaces.  Jet Ice is an all Canadian company that was started in 1979 to make specialty paints and surfactants and a system for ice venues (curling, hockey, bobsled, figureskating ect)Their Jet Gloss - degasification system for optimal strong ice.  This liquid surfactant is added to the ice resurfacing water for the last flood of the day. They say it is designed to remove air trapped in the ice phase, this ice dressing provides a brighter, glossier ice surface.  Like any surfactant this will lower the surface tension of water and allow smaller droplets of water to be formed which possibly helps in making a glossier surface.

So with the help of surfactants (and of course better camera and lighting technologies) you can watch hockey at home or at the arena and see everything better.  You can notice the difference if watch a video from pre-1979 hockey.  You will likely see a very dull nearly brown ice surface.  Today you have a bright surface due to the expertise of the surfactants that the Jet Ice team use.  Check this video out the Guy Lafleur game winner from the 1979 Stanley Cup between the Boston Bruins and Montreal Canadiens. 

And compare it to this brawl between the Boston Bruins and Canadiens brawl a couple of years ago.