Faster, Better, Cheaper, Greener
It is said that the majority of people are ready to do anything to save the planet – so long as it doesn’t cause them any inconvenience or cost them any money.
While this view may be overly cynical, it does contain an important insight – the surest way of getting environmental initiatives to stick is to introduce innovations that either save money or make life easier.
Since most green chemistry initiatives involve eliminating, reducing, or re-using materials, there are often economic gains to be had; the making life easier bit can be a bigger challenge.
Fortunately, in analytical chemistry, automation and miniaturisation go hand in hand, especially where sample preparation is involved. So it is possible to be green, save money and have things easier too.
Recently, I attended a CHEM21 project meeting focussed on making drug development greener; one of the workshops was on the use of metrics to assess the volume and cost of solvent use on drug development.
Anatune develops analytical solutions rather than drugs, but much of the thinking is applicable to what we do and this workshop got me thinking…
Helpfully, one of the organisers pointed me towards a useful metric for analytical methods. In the paper (R. Hartman, 2011) the volume of solvent for the sample preparation and HPLC method is calculated as a volume to component ratio. For example, a method that analyses two components of interest using 50 mL of solvent per run yielded a value of 25 mL per component.
We routinely automate liquid-liquid, liquid-solid and solid phase extraction, so as an example I compared a traditional solid phase extraction (SPE) method, with a similar one utilising an automated, miniaturised SPE approach – something we do all the time.
If we compare the manual SPE method (Figure 1) to the equivalent automated method and we assume there is just one compound of interest in each, then by calculating the AMVI for both sample preparation schemes, we see that for the manual method, we use 22 mL of methanol and 18 mL of water. It uses 40 mL of solvent in total per component; therefore its AMVI is 40:1.
For the automated (miniaturised) method, the volumes of solvents used are reduced (Figure 2). The volumes of solvents for the same extraction are: 1.12 mL of methanol and 580 µL of water. This gives an AMVI of 1.7: 1 mL.
This equates to a greater than 20 times reduction in the environmental impact due to our use of solvents.
This reduction in solvent use has a positive effect on the environmental impact of our work and also has a significant advantage when economic costs are taken into account, as the reduction from 75.6p 1/component to 3.2p/component is nearly a 24 fold reduction in the costs of solvent used. This disparity will only increase as the costs of reagents increases.
A big advantage of, and probably the best selling point for, developing a ‘greener’ method is that it is likely to be very cost efficient too. Something to keep in mind the next time you develop a new method or redevelop an old one.
1Prices taken were for reagent grade solvents and rounded to the nearest pound. Methanol £18/L and Water £20/L.
R. Hartman, R. M.-S. (2011). Analytical Method Volume Intensity (AMVI): A green chemistry metric for HPLC methodology in the pharmaceutical industry. Green Chemistry, 934-939.