Wednesday, July 8, 2015

100 million unique chemical substances registered in CAS database

This year marks the 50th anniversary of CAS Registry and also the 100 Millionth CAS Registry Number. CAS Registry is world’s largest database of unique chemical substances. It identifies each chemical substances with a specific CAS registry number, index name, and graphic representation of its chemical structure. Information in CAS Registry about the many different types of substances includes: synonyms, molecular formulas, ring analysis data, structure diagrams, experimental and predicted property data, and literature references.

Substances included in CAS Registry are from journal articles, patents, chemical catalogs, and reputable web sources from the early 1800s to present. Organic chemicals with MW<1000 are dominant in CAS Registry. In addition to organic chemicals, CAS Registry also include alloys, coordination compounds, minerals, mixtures, polymers, salts, sequences, organometallics, proteins, and inorganic substances.

As chemical innovation continues at the current pace, it is expected chemical substances in CAS REGISTRY in 50 years would be more than 650 million. and the number would be significant higher with the past growth trajectory.

Such large number and fast increasing of chemical substances require high-throughput approaches be applied for hazard and risk assessment and chemical management.

CAS Content at a Glance (

Saturday, June 6, 2015

Plastic microbeads in personal care products

Plastic (mainly polyethylene) microbeads are used in thousands of cosmetics and toothpaste around the world. Plastic microbeads used in personal care products are generally in particle sizes from 10 µm to 100 µm. Such particles serve the function of washing or rubbing a part of the body to remove dead cells from the surface of the skin
photo credit:

Plastic microbeads are used in large quantities and are washed down the drain after use. However, they cannot be efficiently filtered or removed during sewage treatment. As a result, a large amount of plastic particles enter the environment, cause water pollution. Plastic beads eventually end up in the oceans, which are described as "plastic soup" due to a large amount there .   The microbeads are not ready to degrade and can pass through the marine food webs. High concentrations of micro plastic have been found in inland water such as the Great Lakes and in the oceans and also in the body of various marine creatures. 

It is estimated that over 90% of micro plastic in the environment are from the plastic microbeads used in personal care products (Eriksen, Marcus et al. (2013) Microplastic pollution in the surface waters of the Laurentian Great Lakes". Marine Pollution Bulletin 77: 177–182. doi:10.1016/j.marpolbul.2013.10.007). 

Due to the potential environmental problems such plastic microbeads are being removed from personal care products and replaced by naturally biodegradable alternatives by some manufactures.  However, there are still a far cry to say that all personal care products contain plastic microbeads. I recommend we check whether the personal care product we are using still contain environmental unfriendly plastic microbeads from this websites:

Saturday, May 30, 2015

Neonicotinoids pesticides

Recently, the word "neonicotinoids" as a group of insecticides appear frequently in various news reports because the concerns of their association with the increasing mortality rate of honeybees. Because of the potential impact on the pollinators including honeybees, neonicotinoids are at a stage of "near ban". High priority for conducting further risk assessment on neonicotinoids is given by chemical regulations agencies.

Let's have a closer look at neonicotinoids

As indicated by the name, neonicotinoids are related to nicotine.

Neonicotinoids is a group of pesticides most widely used in the world. The group includes






Neonicotinoids act on the central nervous system of insects. Neonicotinoids can bind to some receptors in the nervous system and prevent impulses transmitting between nerves. This biochemical action mechanism would make insecticides exposed to neonicotinoids unable to move and eventually die.

Neonicotinoids have high water solubility and break down slowly in soil. They are often applied to soil and be taken up by plants and provide protection from insects as the plant grows.

When developed, neonicotinoids were claimed to have low-toxicity to many beneficial insects, including bees. However,  toxic effects to bees and other beneficial insects have been realized recently. Bees and other pollinators expose to neonicotinoids through nectar and pollen where neonicotinoids are used in agriculture for pest control. Although the exposed levels are sub-lethal , they may impact some bees’ ability to navigate to flowers and nectar.

Despite some controlled studies, more information is still needed to link neonicotinoids to the bee colony collapse disorder and increased mortality rate of honeybees. However, to keep potential risk to bees and other beneficials low, Corn farmers in Ontario and Quebec are requested to use dust deflectors on their seed planters, and that the seed companies use a seed lubricant to minimize the dust that is emitted during planting.

References and more information:

Friday, May 29, 2015

Natural polychlorinated organic compounds produced by snow flee as predator repellent

A lot of organic pollutants posing negative impact on the environment and on human health are chlorinated. Well known chlorinated hazardous organic chemicals include the well known DDT, PCBs, HCB,  Mirex, Dioxin, etc. All of the 12 persistent organic pollutants (dirty dozens) initially listed in the Stockholm Convention for international regulations are chlorinated compounds. Many of the chlorinated compounds were used as pesticides.

Halogenated organic compounds are seldom found as natural products. Recently, researcher Schulz and colleagues in Germany found one natural chlorinated compounds from the snow flee, a winter-active species of springtail, produces unique polychlorinated octahydroisocoumarins to repel predators. Sigillin A, the active component with five chlorine atoms,  showed high repellent activity in a bioassay with predatory ants.

The snow flee is easily ignored as it is only a few millimeter long, just list some pallets of black pepper on the snow. But such tiny flees have their unique strategy to deal with their predators. They can synthesize their own pesticide Sigillin A to repel ants, spiders etc.

Snow flees are quite efficient at synthesizing Sigillin A. despite Sigillin A is such a complicated organic molecules. Sigillin A synthesized by a snow flee can be 0.2% of it tiny body weight.  It is still unclear whether Sigillin A is synthesized by snow flees themselves or by microorganisms in the body of a snow flee.

Effort has been make to synthesize this natural chlorinated in the lab. Chemists are looking forward to producing this natural chlorinated compound and use it for termite control.

However, natural generated does not mean it is environmental safe when synthesized and used in large quantity. It's environmental persistence, bioaccumulation potential, and toxicity needs to be carefully evaluated before large quantities is produced and used

Friday, April 17, 2015

Green Chemistry

Green chemistry , based on the definition by the USEPA, is a philosophy of chemical research and engineering that encourages the design of products and processes that minimize the use and generation of hazardous substances. 
There are 12 principles involved in Green chemistry
  1. Prevent waste: Design chemical synthesis, purification, analysis processes to prevent waste. Leave no waste to treat or clean up.
  2. Design safer chemicals and products: Design chemical products that are fully effective yet have little or no toxicity.
  3. Design less hazardous chemical syntheses: Design chemical syntheses, purifications, analyses that generate substances with little or no toxicity to either humans or the environment.
  4. Maximize atom economy: Design syntheses so that the final product contains the maximum proportion of the starting materials. Waste few or no atoms.
  5. Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If you must use these chemicals, use safer ones.
  6. Increase energy efficiency: Run chemical reactions at room temperature and pressure whenever possible.
  7. Use renewable feedstocks: Use feedstocks  (also known as starting materials) that are renewable rather than depletable. The source of renewable feedstocks is often agricultural products or the wastes of other processes; the source of depletable feedstocks is often fossil fuels (petroleum, natural gas, or coal) or mining operations.
  8. Avoid chemical derivatives: Avoid using blocking or protecting groups or any temporary modifications if possible. Derivatives use additional reagents and generate waste.
  9. Use catalysts, not stoichiometric reagents: Minimize waste by using catalytic reactions. Catalysts are effective in small amounts and can carry out a single reaction many times. They are preferable to stoichiometric reagents, which are used in excess and carry out a reaction only once.
  10. Design chemicals and products to degrade after use: Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.
  11. Analyze in real time to prevent pollution: Include in-process, real-time monitoring and control during syntheses to minimize or eliminate the formation of byproducts.
  12. Minimize the potential for accidents: Design chemicals and their physical forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires, and releases to the environment.

Sunday, March 29, 2015

Modern analyses of ancient beer

A recent issue of the Journal of Agriculture and Food Chemistry published an interesting article on chemicals in beers from an 1840s’ shipwreck. 
(photo source:, Image credit: John Londesborough et al.) 

In 2010, underwater archaeologists discovered an old schooner south of the Åland Islands at a depth of 50 m in the Baltic Sea. Archeological evidence suggests the shipwreck occurred during the 1840s, but the schooner’s name, its destination and its last port-of-call were not identified. Archeologist brought the cargo consisting of luxury items, including more than 150 bottles of champagne and five bottles that look like typical early 19th century beer bottles to the surface. One of these cracked in the divers’ boat. The liquid that foamed from the cracked bottle looked and, according to the divers, tasted like beer.

Researchers from Finland analyzed two bottles of the beer from the shipwreck  and six bottles of modern  beers (Leffe Brune, Koff Porter, Weihenstephan Hefe Weissbier, Paulaner Hefe Weissbier, Aldaris Porteris Alus, and Olvi Sandels) as reference. The founding provides clues for beer makers to resurrect the flavors of ages past.

The beer samples were degassed by ultrasonification and filtered (0.45 μm). An aliquot (5 μL) was loaded to an HPLC-MS/MS system (high performance liquid chromatography coupled with tandem mass spectrometry) and analyzed for hops related compounds (native or degradation products).

Sidenote (from Wikipedia): Hops are the female flowers of the hop plant, Humulus lupulus.

Hops are used primarily as a flavoring and stability agent in beer. Hops impart a bitter, tangy flavor to beer. Hops have antibacterial effect that favors the activity of brewer's yeast over less desirable microorganisms and for many purported benefits such as balancing the sweetness of the malt with bitterness and contributing a variety of desirable flavors

Above: Chemical structures of bitter chemicals identified in hops and freshly brewed beer; Below: Chemical structures of bitter chemicals identified in aged beer (Source: J. Agric. Food Chem. 2010, 58, 7930–7939)
Based on the chemical fingerprint in the beer, the two bottles of ancient beer were identified as two different kind of beer.  One was more strongly hopped than the other. 

High levels of organic acids, carbonyl compounds, and glucose indicated extensive bacterial and enzyme activity during aging. However, concentrations of yeast-derived flavor compounds were similar to those of modern beers, except that 3-methylbutyl acetate
was unusually low in both beers and 2-phenylethanol
and possibly 2-phenylethyl acetate
were unusually high in one beer. Concentrations of phenolic compounds were similar to those in modern lagers and ales

Besides hops related chemicals, the researchers also analyzed other chemical components in the ancient beer. Compared to typical modern lagers and ales, ethanol contents of the shipwreck beers were low (2.8-3.2%). Glycerol and ethanol had a ratio of 4.5% for both shipwreck beers, which is typical for a yeast fermentation product. Both beers were acidic, but their pH were ~1 below modern values. The color strengths were in the range of modern ales and lagers, and much lower than porters or stouts. Possibly been oxidized after over the 170 years, sulfur dioxide was not detected in shipwreck beers. Protein levels were very low in both beers.

  • John Londesborough, Michael Dresel, Brian Gibson, Riikka Juvonen, Ulla Holopainen, Atte Mikkelson, Tuulikki Seppänen-Laakso, Kaarina Viljanen, Hannele Virtanen, Arvi Wilpola, Thomas Hofmann, and Annika Wilhelmson J. Agric. Food Chem. 2015, 63, 2525−2536 DOI: 10.1021/jf5052943 Analysis of Beers from an 1840s’ Shipwreck 2015, 63 (9), pp 2525–2536
  • Gesa Haseleu, Annika Lagemann, Andreas Stephan, Daniel Intelmann, Andreas Dunkel and Thomas Hofmann. Quantitative Sensomics Profiling of Hop-Derived Bitter Compounds Throughout a Full-Scale Beer Manufacturing Process. J. Agric. Food Chem., 2010, 58 (13), pp 7930–7939 DOI: 10.1021/jf101326v

Saturday, March 14, 2015

Purifying urban air with pavement containing titanium dioxide

A recent study published in the journal of Atmospheric Environment by Folli et al. demonstrated the effectiveness of cleaning NOx in urban air via photocatalytic oxidation using titanium dioxide as semiconductor photocatalyst added to pavement.

(source of image:

The advantage of such technology is that photocatalystic oxidation only requires sunlight, existing oxygen and water in air. Therefore, remediation is continuous in day light.

In this study, researchers conducted a year-long field test in the city of Copenhagen. They employed two continuous air monitoring stations, one in the area with photocatalytic concrete pavers and the second one in the area without photocatalytic concrete and assessed the effectiveness of TiO2 containing pavement in removing NOx in the air.

The study indicates that a monthly abatement of NO was around 22% in the summer months;
NO noon abatement was >45% at the summer solstice, which corresponded to NOx noon abatement > 30%.

Personally, I think such technology is very promising although more research work needs to be done. Research questions worth to be addressed include but not limited to

  • Does the technology also has the benefit of degrade other toxic chemicals in urban air such as polycyclic aromatic compounds?
  • What's the over all benefit of such technology if widely used in urban pavement and building walls and how does the benefit of removal toxic chemicals compared to the cost. 
  • What degradation products can be generated and how do they affect urban air and environmental quality? 

 In addition to the article by Folli et al. mentioned above, the following articles on the removal of pollutants by adding TiO2 in cement are also informative on this topic.

  • Folli, J.Z. Bloh, M. Strøm, T. Pilegaard Madsen, T. Henriksen, D.E. Macphee Efficiency of solar-light-driven TiO2 photocatalysis at different latitudes and seasons. Where and when does TiO2 really work? J. Phys. Chem. Lett., 5 (5) (2014), pp. 830–832
  • J. Ângelo, L. Andrade, L.M. Madeira, A. Mendes An overview of photocatalysis phenomena applied to NOx abatement J. Environ. Manag., 129 (2013), pp. 522–539
  • M.M. Ballari, H.J.H. Brouwers Full scale demonstration of air-purifying pavement J. Hazard. Mater., 254–255 (2) (2013), pp. 406–414 URL