Chemistry – Page 38 – David Bradley

Solvent abuse

Adolescent drug use has fallen overall since the late 1990s, but the “recreational” use of solvents is on the increase. Solvent, or inhalant, abuse is now the fourth most abused drug among US teens according to NIDA.

Inhalants, which include volatile organic compounds such as butane and aromatic hydrocarbons (like toluene) activate the same areas of the brain as do other drugs of abuse. However, understanding their precise mode of action has not been clarified until now.

Toluene is found in paint thinners, varnishes and even nail polish remover and is commonly abused and new research shows that it stimulates dopamine release in specific regions of the brain known as drug reward pathways. The results, obtained by Arthur Riegel and colleagues at the Vollom Institute, in Portland, Oregon, suggest that the brain interprets inhalation of toluene as a rewarding experience which can result in continued abuse and re-abuse.The findings could help in developing strategies to prevent and treat addiction to substances containing toluene.

Surprisingly, researchers also found that toluene-containing substances are most effective at low concentrations. Since toluene is rapidly absorbed by the brain, this might explain why the preferred mode of delivery is by “huffing” or “sniffing”. Sniffing is frequently considered a harmless recreational or party drug but unlike other drugs, even a single session of inhaling the compound can disrupt heart rhythms enough to cause cardiac arrest and lower oxygen levels enough to cause suffocation. Not a good thing.

The research is published today in the journal Neuropsychopharmacology.

New York Smells

Today, the New York City authorities were investigating a persistent smell of “gas” across a large part of the lower Manhattan area of the city.

Hundreds of people reported the odd, but apparently not noxious smell, to the New York Police Department, but at the time of writing the identity of the gas remained unknown. Despite this, Mayor Michael Bloomberg somehow manages to make confident proclamations that the gas is “not dangerous”.

Over on Digg, a heated debate has been raging since the first news of the mystery smell was released on an unsuspecting public. Some members of the so-called online “news” community, claim to live in NYC and that there is no smell. Others muse that Howard Stern is to blame, while yet others are confused as to whether this represents a homeland security issue.

Some New Yorkers are saying the gas smells of gasoline (petrol to those of us this side of the pond), while others reckon it’s more like natural gas (methane, of course, has no odour so a very strong smelling sulfur-containing compound – mercaptan – is added in tiny amounts to give it a smell).

The BBC reported that the source was across the Hudson River in New Jersey, where officials said a natural gas leak originating in the Chelsea district of Manhattan, had occurred.

New York, new york, so good they named it twice…

Knights of the chemical realm

Right royal honours were bestowed on two of my very oldest contacts in the field of chemistry this week. Royal Society of Chemistry president Professor Jim Feast was awarded the CBE in the New Year Honours List for ‘services to polymer chemistry.’ And, supramolecular ex-pat Fraser Stoddart was given a Knighthood for to ‘services to chemistry and molecular nanotechnology.’

Congratulations to them both. With such accolades under their belts, it’s surely only a matter of time before either one of them gets that phone call from Stockholm too.

RFID for chemicals

RFID for molecules A new type of radio frequency identification (RFID) sensor for gaseous molecules has been created based on a standard RFID tag coated with a chemically sensitive film at low cost. The use of multivariate analysis allows these new RFID sensors to be used to identify and quantify vapours important to industrial, in health, law enforcement, and of security applications.

Radislav Potyrailo and William Morris of the Materials Analysis and Chemical Sciences Technology at General Electric Global Research Center, in Niskayuna, New York, explain the benefits of their new technology in a forthcoming issue of the journal Analytical Chemistry. “Distributed sensor networks are critical for numerous applications such as monitoring of transport of pollution plumes across the perimeters of industrial plants, leak detection from storage tanks, health monitoring of buildings, large-area tracking of contamination sources in natural water supplies, and spatially resolved combinatorial screening of materials,” they explain.

More…

Scratchy and itchy

Researchers are only just begin to scratch the surface of the brain with functional MRI. Now, a study of perception in both allergen- and histamine-induced itch has revealed how different parts of the brain are activated in response to stimulation from each type.

Allergens, such as pollen and dust, and histamine released by allergy cells as a result of activation by foods, drugs, or infection often lead to a vicious itch?scratch cycle as any allergy sufferer will tell you. However, researchers at Oxford University have demonstrated that the brain responds differently to itchiness caused by allergens and histamine.

Siri Leknes, Susanna Bantick, Richard Wise, and Irene Tracey at Oxford have worked with Carolyn Willis and John Wilkinson of the Department of Dermatology, at Amersham Hospital to try to understand the nature of itch? cycle with a view to improving outcomes for allergy sufferers and people with certain chronic skin conditions.

Read on in the latest science news round-up from David Bradley on spectroscopynow.com

Being particular about DNA

Surface-enhanced Raman spectra (SERS) of DNA and RNA mononucleotides can be detected with high sensitivity, according to UK researchers. Using citrate-reduced silver colloidal nanoparticles aggregated with magnesium sulfate instead of the more common halide ions, reduces inappropriate enhancements and produces spectra that are sufficiently different to allow each to be distinguished.

“The main advantage of our SERS approach is that it allows direct label-free identification of mononucleotides in aqueous solution,” Steven Bell, Director of the Innovative Molecular Materials Group, at Queen’s University Belfast, explains, “There is no requirement for labels because the Raman signals of each of the mononucleotides are intrinsically different due to the differences in their chemical structures.” He adds that spectra can be obtained at ten nanograms per millilitre. “We were working with large samples but reducing the sampling volume to a few microlitres would move the sample down to tens of picograms,” he says.

More…

Nervous scoop

An action shot of the protein Scp1, which plays a crucial role in the development of the nervous system has been obtained using crystallography by researchers in the US. Their structure could provide drug designers with a template for creating small molecule inhibitors of this protein that would be useful in neurological research.

Joseph Noel and Samuel Pfaff of the Salk Institute for Biological Studies and colleagues there and at the University of California, San Diego (UCSD) and The Scripps Research Institute, La Jolla explain that a network of signalling molecules controls embryonic stem cell differentiation. Controlling the controllers might allow scientists to nudge embryonic stem cells into becoming specific cell types, which would be useful in basic research and for potential therapies.

Read on…

Analytical techniques clean up diesel

Raman spectroscopy, X-ray diffraction, and electron microscopy could help diesel engine components manufacturers meet tough new emissions regulations, according to researchers at Oak Ridge National Laboratory’s High Temperature Materials Laboratory (HTML).

The techniques can provide detailed characterizations of materials and allow components to be tested for heat and stress effects more effectively as part of the industry’s preparation for new emissions mandates that come into effect in the US in 2007. Under the new laws, a 90% reduction of nitrogen oxide, NOx, and particulates from diesel vehicles will be required.

“Environmental Protection Agency regulations are pushing emissions control technology very hard,” explains Arvid Pasto, director of the HTML, “so that engine and emissions control equipment manufacturers require access to very sophisticated tools to develop this technology. Fortunately, our user facilities are well equipped to help them.”

Diesel engine-maker Cummins, for instance, has used HTML’s analytical capabilities to better understand the properties of materials used in exhaust after-treatment systems. In addition to studying how catalysts can be adversely affected by sulfur and other gaseous exhaust components, Cummins and HTML have worked together to characterize the fatigue life of cordierite diesel soot filters, which remove more than 98% of particulate emissions from diesel exhaust. These exhaust after-treatment devices are critical to meeting upcoming emissions requirements.

Another company Industrial Ceramic Solutions, of Knoxville, Tennessee, used HTML’s scanning electron microscope facility to analyse material being developed for ceramic-fibre diesel particulate exhaust filters. The original material did not function as well as competing products and had a tendency to crack. The tests revealed that the fabrication process was to blame and ICS has modified its process to improve the product.

‘The sophisticated electron microscopy at HTML allowed our small business to literally look inside of the ceramic fiber filter media at thousands of times magnification,’ said Richard Nixdorf, ICS president and CEO. ‘This information led ICS to solutions that eliminated micro-cracking and moved our filter-media strength far beyond what the diesel exhaust filter application demanded.

Chemistry News

More chemical news from the current issue of Reactive Reports, now online.

Bedwetting Chemistry – A higher concentration of sodium and urea in urine could underlie a type of bedwetting in children that does not respond to the common medication, desmopressin.

Rubber Suits You Sir – Military personnel, chemical workers, and others could benefit from a new synthetic rubber material tailored with liquid crystals.

Biomolecules Out on a Wing – Photonic crystals give butterflies their beautiful colors and synthetic versions are now being developed for a range of technological applications.

Salt and the Boiling Point of Water

TL:DR – If you dissolve salt in water, you raise its boiling point. Similarly, you also lower its freezing point. These effects occur with any solute dissolved in any solvent and depend on how many solute particles are dissolved in the solvent. The key phrase is colligative properties.

Colligative properties include: Relative lowering of vapour pressure (Raoult’s law), elevation of boiling point, freezing point depression, osmotic pressure.

Colligative properties determine how a solvent will behave once a solute is added to make a solution. The degree of change depends on the amount of solute dissolved in the bulk liquid, not the type of solute. So, without my doing your homework for you…how does adding salt to water affect its boiling point? You will find several clues and several keywords above and below.

The fact that dissolving a salt in a liquid, such as water, affects its boiling point comes under the general heading of colligative properties in chemistry. In fact, it’s a generic phenomenon dissolve one substance (the solute) in another (the solvent) and you will raise its boiling point.

So, here’s a rough explanation of what’s going on. If a substance has a lower vapour pressure than the liquid (it’s relatively non-volatile in other words) then dissolving that substance in the liquid, common salt (NaCl) in water (H₂O), for instance, will lower the overall vapour pressure of the resulting solution compared with the pure liquid. A lower vapour pressure means that the solution has to be heated more than the pure liquid to make its molecules vaporise. It is an effect of the dilution of the solvent in the presence of a solute. If you want to know about tungsten and why it is used in incandescent light bulbs please check out the Wikipedia entry.

Put another way, if a solute is dissolved in a solvent, then the number of solvent molecules at the surface of the solution is less than for pure solvent. The surface molecules can thus be considered “diluted” by the less volatile particles of solute. The rate of exchange between solvent in the solution and in the air above the solution is lower (vapour pressure of the solvent is reduced). A lower vapour pressure means that a higher temperature is necessary to boil the water in the solution, hence boiling-point elevation.

Conversely, adding common salt to water will lower its freezing point. This effect is exploited in cold weather when adding grit (rock salt) to the roads. The salt dissolves in the water condensing on the road surface and lowers its freezing point so that the temperature has to fall that bit more before ice will form on the roads.

A much more fun use for freezing point depression is to add salt to ice to make ice cream. The About site has some instructions on how to do this, although it’s probably not too tasty.

Curiously, at least one Sciencebase reader was searching for the phrase “how does sugar affect the boiling point of water?” and landed on this page. This is essentially the same question as, “does salt affect the boiling point of water?” The nature of the solute, the material being dissolved in the solvent, is pretty much irrelevant at a first estimate. Rather, it is the amount of material that is dissolved (which depends on the materials solubility) that influences the boiling and freezing points as described above.