by: Jack McAlpine
When I moved into my first apartment, my roommate and I were very excited to start our new independent lives. We unpacked all our things, set up our rooms, and went to the grocery store. It had been a long day and I was ready to eat dinner. When I got back home and started to cook, we realized that neither of us owned any knives. However, we owned three colanders. This lack of preparedness has been very similar to starting up the lab. All the small components of everyday life that you take for granted are no longer there. Everything needs to be purchased: solvents, instruments, and so many gloves. There is also a lack of experience. The three of us starting the group do not know that much about the field we jumped into and cannot lean on our PI every time we have a question. We needed different tools to be prepared for the road ahead.
Being prepared for a situation starts with understanding dangers and limitations. I was once touring a facility that worked with radioactive materials. The scientist giving the tour stated he feared some of the things he worked with, but he was “not scared scared but scared prepared”. He could do his job effectively and respect the hazards involved because he knew enough about what he was working with to avoid the dangers. For us in the new lab, learning some of the basic features of ionic liquids was a first step toward being prepared. Several unique properties of ionic liquids are listed in the first couple paragraphs of most papers you read about the materials. Ionic liquids have a large electrochemical stability window, high viscosity, and negligible vapor pressure1. These seemed like a starting point for understanding.
The large electrochemical window and high viscosity have minimal impacts upon safety. However, from the perspective of safety, a low vapor pressure is great. Vapor pressure is a measure of the concentration of a material in the gas phase at equilibrium. So, a higher pressure leads to a material evaporating quickly and becoming more present in the surrounding atmosphere. This can lead to inhalation of toxic chemicals, think of the smell of paint thinner or nail polish remover. The scents are strong because of the higher vapor pressure. Another concern with using materials with high vapor pressures is flammability. Solvents like ethanol, benzene, and propylene carbonate can become a fire hazard if left open for too long2. The low vapor pressure of ionic liquids makes them a safer material to work with in this regard.
Vapor pressure can be thought of as how quickly a material can evaporate. Here, the molecules are represented by circles. At low vapor pressures, most of the material is liquid but as vapor pressure increases, there is more of that molecule in the gas phase (Image from the Gebbie Lab).
It makes sense that only the positive aspects would be listed at the beginning of literature and may overlook other safety concerns. For safety information a researcher should turn the to the safety data sheet (SDS). The SDS is a standardized document that outlines the hazards of a specific material. These need to be supplied by the manufacturer of the chemical and can commonly be accessed on the producer’s website. Reading over these reveals that many ionic liquids and the salts used in their synthesis can cause severe eye irritation and skin burns3. Of greater concern is that ionic liquids are very hygroscopic4. This means that they readily absorb water from the atmosphere. Some salts have such a high affinity for water that a crystal can become a water-in-salt mixture from being left open to the atmosphere. While this is cool to watch, it means that cleaning counters produces hazardous waste.
These pictograms are standardized by the UN to represent different hazard types. Chemicals may have one or more of these on their label and SDS (Image from Wikimedia Commons).
Chemical burns are nasty, and we need to protect our eyes and skin. Protecting eyes is easy enough, any researcher should wear safety glasses while working in a lab. Protecting hands also seems like it should be easy enough, wear a pair of gloves. But which gloves do you wear? The answer seems simple, whatever protects you the most. Sadly, there is no perfect glove. All materials are permeable to some chemicals, degrade in others, and have different levels of comfort. Nitrile gloves are the workhorse of chemical research. They are cheap, flexible, and comfortable when it comes to skintight gloves. Nitrile gloves are not perfect and are permeable to several common solvents, like acetonitrile. While coming into contact with acetonitrile does not immediately make your hand wet, the chemical will slowly make its way through the glove carrying any other possibly harmful chemicals with it. The glove needs to be replaced to prevent contact and harm. We work with acetonitrile and need a glove that will protect us. Butyl gloves are one of the only gloves that provide great protection against acetonitrile and we bought some5.
These are some gloves that we considered. An example of nitrile gloves is the bright blue glove on the right side of the image, a butyl glove is to the lower left (Image from Wikimedia Commons).
Butyl gloves are nothing like nitrile gloves. Butyl gloves are thick, cover part of the forearm, and do not get replaced after use. These gloves make it hard to hold small objects and perform more delicate motions. We cannot wear butyl gloves around the lab if we wish to type, write, or measure out samples. As a result, we limit the amount of time we wear butyl gloves. When performing tasks that require minimal dexterity butyl gloves are used. Otherwise, nitrile gloves are worn. Is it the safest option? I would argue it is. The butyl gloves are too clunky for me to handle small things without fear of dropping them. Nitrile gloves need to be replaced immediately after any spill. While permeable to acetonitrile, the rate at which the solution permeates the glove is slow enough that a research can safely stop the task they were performing and then replace their glove.
Reading the SDS and wearing certain gloves is only the beginning. As the group grows and more equipment is bought, different hazards will be introduced to the lab. An early focus on safety helps us stay ahead of the ever-present dangers. This way new researchers who join the lab and are unprepared can easily access the tools they need to be safe and successful.
- Lockett, V., Sedev, R., Ralston, J., Horne, M., & Rodopoulos, T. (2008). Differential capacitance of the electrical double layer in imidazolium-based ionic liquids: Influence of potential, cation size, and temperature. Journal of Physical Chemistry C, 112(19), 7486–7495. https://doi.org/10.1021/jp7100732
- Transport Canada, and Security Group. “Assessing Hazards: Importance of Vapour Pressure.” Transport Canada, 6 Nov. 2009, tc.gc.ca/eng/canutec/articles-vapour-437.htm.
- “1-Allyl-3-Methylimidazolium Bis(Trifluoromethylsulfonyl)Imide 727695.” Sigma, www.sigmaaldrich.com/catalog/product/aldrich/727695?lang=en&
- Adibnia, V., Mirbagheri, M., Latreille, P. L., De Crescenzo, G., Rochefort, D., & Banquy, X. (2019). Interfacial Forces across Ionic Liquid Solutions: Effects of Ion Concentration and Water Domains † [Research-article]. Langmuir, 35(48), 15585–15591. https://doi.org/10.1021/acs.langmuir.9b02011
- “Glove Selection Chart.” Glove Selection Chart, Augusta University, www.augusta.edu/services/ehs/chemsafe/PDF files/gloveselechart.pdf.