Safety during ultrasonication

James Bond in Casino Royale shoots a propane tank with a handgun. You didn’t miss that did you? If you did, do you at least remember what happens when a gas tank explodes after a crash in Terminator 2: Judgment Day? It’s okay if you don’t, because I’m going to tell  you what happened when the famous ‘rainbow experiment’ went wrong in a lab. Not once but twice.

Chemicals are as nasty as they are shown in films. Chemicals are also very noxious in a chemical laboratory as much as they are at any place else. That’s why wherever you are, whatever you do, chemicals should be handled with care. (Girls, even the acetone that you use to remove nail polish from your nails can catch fire as soon as it comes in touch with an ignition source, i.e. fire.)

Coming to the rainbow experiment. It’s really fascinating to look at. What happens is, when elements such as Na, Sr, K, Li and Cu are mixed with methanol and ignited, they all burn in the colors of a rainbow. You can see its video here.

What went wrong with the rainbow experiment?

A teacher’s chemistry experiment exploded during a demonstration at Beacon High School in Manhattan on Thursday, creating a fireball that burned two 10th graders, one severely, according to Fire Department and school officials. – Chemjobber

It is better to be safe than sorry. As you can see, horrible things have happened, not only to grown-ups but also to children. This doesn’t meant you should avoid doing things that involve risks. Instead, you can do it in a safe way.

As students who had to work in a laboratory, we were told by our professor (Prof. Bhujle) to learn the safety aspects of our respective projects. For those who do not know me or what I was up to during my Masters degree, here’s what I did:

Process intensification using alternative energy source i.e. ultrasound irradiation (sonochemistry), which leads to decrease in energy consumption and waste reduction. Also investigated a Lewis acid catalyzed homogeneous organic condensation reaction and an ultrasound-assisted Pd-catalyzed heterogeneous transfer hydrogenation reaction.

Safety aspects associated with the project:

Ultrasound usage can be categorized as:

  • Low frequency, high power ultrasound (20–100 kHz)
  • High frequency, medium power ultrasound (100 kHz–1 MHz)
  • High frequency, low power ultrasound (1–10 MHz)

The equipment I used to generate ultrasound i.e. ultrasonic bath, runs on a 33 kHz frequency. Hence, it can be taken as low frequency, high power ultrasound.

Contact Exposures:

Contact exposure is exposure for which there is no intervening air gap between the transducer and the tissue. This may be via direct and intimate contact between the transducer and the tissue or it may be mediated by a solid or liquid. Contact exposure can in some cases provide nearly 100% energy transfer to tissue. [1] 33 kHz frequency ultrasonic bath can cause observable effects.

Airborne ultrasound:

The most plausible mechanisms for non-auditory effects of airborne ultrasound on a human are heating and cavitation. [1] An exposure limit for the general public to airborne ultrasound sound pressure levels (SPL) of 70 dB (at 20 kHz), and 100 dB (at 25 kHz and above). [2] The major effects of airborne ultrasound of concern in practice are the result of reception by the ear. To summarize, exposure to ultrasonic radiation, when sufficiently intense, appears to result in a syndrome involving manifestations of nausea, headache, tinnitus, pain, dizziness, and fatigue. The type of symptom and the degree of severity appear to vary depending upon the actual spectrum of the ultrasonic radiation and the individual susceptibility of the exposed persons, particularly their hearing acuity at high frequencies. A concise summary of the physiological effects of ultrasound with specific stated exposure conditions has been given by Acton.

Measures to be taken for safety:

  • Contact exposure to high-power ultrasound must be avoided at all times. [1]
  • Only operators qualified to use the equipment or persons under strict supervision should be allowed within the boundaries of the controlled area while the equipment is operating. [1]
  • Personnel using high-power ultrasound, and safety inspectors in industry should be knowledgeable about the possible harmful effects of ultrasound and necessary protective measures. [1]
  • Warning signs should be placed at the entrance to any area which contains high power ultrasound equipment or applied to each high power ultrasound device. Accompanying each warning sign there should also be a statement indicating the precautionary measures to be taken while the ultrasound power is on. [1]
  • Safety procedures for the protection of personnel are similar to those used for audible noise. The protection for ultrasonic frequencies is expected to be at least 14 dB for ear muffs and rubber ear plugs, and 24 dB for foam ear plugs. [1]

References:
1. Guidelines for the Safe Use of Ultrasound Part II – Industrial & Commercial
Applications – Safety Code 24. Health Canada. ISBN 0-660-13741-0, (1991).
2. AGNIR (2010). Health Effects of Exposure to Ultrasound and Infrasound. Health
Protection Agency, UK, 167–170.

I’ll discuss transfer hydrogenation in subsequent blog posts.

Stay safe. ;)

Chemistry with glasses on

I’m going to take you back in time. Forget all the chemistry you know for the next few seconds – say three. Can you wonder how it must have been to think, ‘Hey, this material must have some structure.’? Sounds bizarre. As bizarre as Newton asking himself, “Why does anything fall?’

These three scientists wondered about chemical structures in the same bizarre way and are the founders of the theory of chemical structure.

  1. Alexander Mikhaylovich Butlerov, a Russian chemist, one of the principal creators of the theory of chemical structure.
  2. Archibald Scott Couper, a Scottish chemist who proposed an early theory of chemical structure and bonding.
  3. August Kekulé, German organic chemistHe was the principal founder of the theory of chemical structure.

First glass

In 1951, physicist Erwin Wilhelm Müller,  a German physicist, was the first to see atoms. He did this using his own invention: the field ion microscope. Literature doesn’t have the photograph of what he saw but the following photograph is similar to what he observed: each dot is the image of an individual platinum atom.

(Image: ACS)

Second glass

In 1931, Max Knoll and Ernst Ruska built the first TEM. In 2013, researchers put this to use by observing what happens inside a battery. The following image is a TEM image of the polio virus.

(Image: Wikipedia)

Third glass

The third glass quickly replaced the second in the year 1952 when the following photo was captured. But it was rather an indirect picture – Photo 51. Photo 51 is the nickname given to an X-ray diffraction image of DNA taken by Raymond Gosling  in the lab of Rosalind Franklin, as her PhD student.

(Image: Wikimedia)

Fourth glass

The fourth glass was put on with the advent of scanning tunneling microscope. This gave rise to a technique called as scanning probe microscopy. Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very high-resolution type of scanning probe microscopy. In 2009, a single molecule was imaged for the very first time by IBM researchers. This was done by using a AFM. It is with AFM that for the very first time (2013) that scientists saw how hydrogen bonds looks like. The following is its picture.

(Image: RSC)

Fifth glass

The fifth glass is our very own digital camera.

“A great deal of time is spent within synthetic chemistry laboratories on non-value-adding activities such as sample preparation and work-up operations, and labor intensive activities such as extended periods of continued data collection. Using digital cameras connected to computer vision algorithms, camera-enabled apparatus can perform some of these processes in an automated fashion, allowing skilled chemists to spend their time more productively. In this review we describe recent advances in this field of chemical synthesis and discuss how they will lead to advanced synthesis laboratories of the future.” – Abstract from an open-access paper ‘Camera-enabled techniques for organic synthesis‘ (Beilstein J. Org. Chem. 2013, 9, 1051–1072.)

Researchers from UCLA have developed a smartphone microscope to see single virus and synthetic nanoparticles. It produces images almost as good as a SEM.

(Image: geek.com)

Sixth glass

Last week, I attended a lecture by Prof. Prashant Jain (nanogold.org) from the University of Illinois, at ICT, Mumbai. It was called ‘Elucidating chemical reactions on the nanoscale’. He described how we can observe individual nanoparticles instead of observing the reaction in bulk. His research involves ‘Imaging Phase Transitions in Single Nanocrystals’. The following is a section from his profile describing this research work.

Phase transitions in solid-state materials often involve interesting dynamics. Since macroscopic solids are typically polycrystalline, such dynamics is smeared out in studies on bulk solids, due to ensemble averaging over different crystalline domains. By acquiring snapshots of a single nanocrystalline domain undergoing a phase transition, our lab is attempting to uncover the dynamic trajectory involved in the nucleation of a new phase. We are developing new optical and spectroscopic methods to acquire snapshots of model phase transitions and also using these techniques to learn new facts about fundamental phenomena such as crystal growth, impurity doping, and correlated electron systems.

We’ve come a long way observing chemistry, haven’t we? The more we see, we find how less we know.

Acknowledgment: Thanks to Dirk Schweitzer for introducing me to the paper – ‘Camera-enabled techniques for organic synthesis‘. You can find him on Google+.

New in Green Chemistry: The Zipper approach

Many chemical products can be produced via different routes. One of these routes may be industrialized depending upon its cost-effectiveness, satisfaction of environmental constraints and ease of scale-up. As you may be aware, environmental constraints have become stringent due to the effects the chemical and allied industries have on our environment. Green Chemistry, with its 12 guiding principles has made the world look at conventional chemistry and its subsequent scale up with a fresh approach that is environmentally benign.

In 1990, Elias James “E.J.” Corey, an American organic chemist won the Nobel Prize in Chemistry for his development of the theory and methodology of organic synthesis, specifically retrosynthetic analysis. The most famous of all the restrosynthesis processes is the production of Ibuprofen, wherein 6 steps were reduced to just 3. This achieved one of the 12 principles of Green Chemistry that says, “Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.”

Synthesis Explorer by the Royal Society of Chemistry (RSC) helps students and teachers plan synthetic routes by choosing a starting compound, reacting it and viewing details of the reaction.

According to Warner, only 10 percent of current technologies are environmentally benign and 35 percent could be made benign relatively easy. The remaining 65 percent will need to be reinvented in more environmentally benign ways. A report by Lisa Lilleland, a sustainability advisor and environmental advocate.

Retrosynthesis is design of organic synthesis to find newer, simpler and benign ways to produce a compound. Technion Scientists have now developed a new method for selective synthesis of complex molecules. They call it the “Zipper Approach”. It is a one-of-a-kind stereochemistry for difficult transformations: allylic C-H (H=Hydrogen) and selective C-C bond activations. The paper is published in the journal Nature.

More and more companies are now offering services in upscaling and route scouting. Route scouting is the creation of sustainable synthesis routes. Some of the companies that provide such services are:

Learning from nature

Why make our own mistakes when we can learn from nature? Through unfathomable amounts of trial and error that nature has gone through, it would only be wise to learn how nature does what it does. Biomimicry is what we name – our process of learning from nature. The earliest of examples of biomimicry has been the making of an aeroplane. It is when we tried to see how birds do it is when we understood how humans could fly too. Sonar technology was invented after studying the echolocation that bats use to navigate.

2013-09-07 17.34.53 (1)Green Chemistry and Biomimicry:

Green Chemists too can learn from it as sustainable chemistry is what nature is good at. Nothing goes to waste you see? It is in nature lies the secrets of producing inherently safer chemistries. The enzymes that are at work in our body right now are natural catalysts. This gives rise to bio-catalysis. Learning from corals that fix carbon to create vaccines that do not need refrigeration are few of the many applications that have their origins in biomimicry.

Let’s also see how nature has inspired industries.

Paper and pulp industry:

Paper is made from wood fibres that are bonded together by a natural adhesive known as lignin. Lignin must be removed in order to make paper. While one may think of lignin as waste, it is not. Lignin after separation is used for producing other chemicals and may be also to produce an oddly sounding product called ‘liquid wood‘, a plastic replacement. This entire process is called ‘pulping’ and is done through physical and chemical processes. These processes are water and energy intensive. To ensure that less water and energy is used, scientists have come up with a solution that uses a deep eutectic solvent. These solvents occur naturally: plants produce them during droughts.  Not only that, these scientists used the genius of penguins to solve the problem of high water usage during the drying process that follows pulping. To escape from seals underwater, these birds release trapped air bubbles which form a thin layer of air around their plumage, reducing friction. This gave the researchers an idea to suspend the fibres in a viscous fluid and then expel the fluid by modifying the viscosity around the fibres.

Fuel industry:

Plants are very efficient machinery that can store sunlight directly into storable chemical form. Researchers led by a MIT professor produced something known as a ‘artificial leaf’, a device that can harness sunlight to split water into hydrogen and oxygen without needing any external connections, just like leaves do.

Solar industry:

In the field of solar energy, plants are an exemplary. Have you seen the sunflowers move as they track the position of the sun in the sky for maximum absorption of solar energy? That’s something to learn from and scientists have come up with sunflower-inspired solar panels that track the sun without using motors. Another example of biomimicry in this industry are the dye-sensitized solar cells, that are solar cells inspired by photosynthesizing plants.  Along similar lines, researchers at the Institute of Chemical Technology (ICT) (the institute I majored from) have developed 18 synthetic dye molecules, which can be used to make indigenous dye-sensitised solar cells (DSC) that absorb solar energy.

Windmill industry:

To reduce the drag in wind turbines, some researches decided to use the riblet technology. The channeling effect was first noted in shark skin research in the 60s and 70s, which was first studied by NASA to incorporate it into aerospace engineering.

Water-treatment industry:

Discovery of aquaporins, integral membrane proteins that form pores in the membrane of biological cells, are nature’s very own filters. Inspired from this a Danish company Aquaporin has developed a new approach to seawater desalination.

To know more about such extraordinary lessons on conservation of material and energy, go to AskNature.

Here’s a mind boggling video of the physics of water in trees. Do you think we can take away something from this as well?

Design of experiments

It is a such a mess without proper organization and good design of experiments. Without proper organization and good design of experiments you lose time, energy, resources and peace of mind. Design of experiments should be a requisite for greener research.

Many of the current statistical approaches to designed experiments originate from the work of R. A. Fisher in the early part of the 20th century. Fisher demonstrated how taking the time to seriously consider the design and execution of an experiment before trying it helped avoid frequently encountered problems in analysis. Key concepts in creating a designed experiment include blockingrandomization and replication.

Learn more:

DOE

Information and Economics in Fisher’s Design of Experiments

Go Planet!

I grew up watching Captain Planet and the Planeteers, an American animated environmentalist television program. I used to like the idea of doing something for planet earth. But as I grew up, I read and heard about the problems our earth is facing, the politics and most importantly how incomplete my knowledge is. In the process, I only learnt to keep an open mind.

“Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense.” – Buddha

Last Edited: January 9 2018