Penalty points are based on how much chemicals we use, and how dangerous they are. The number of penalty points are subtracted from 100, and if this final score is higher than 75, which means no more than 25 penalty points, the method represents excellent green analysis. In our case, LC-MS contributed with 12 penalty points, while the standard sample preparation contributed with 29 penalty points and 800 mg waste of chemicals. In combination, this gave a score of 59 (acceptable green analysis). Using our LPME method, the total score improved to 78, and the waste of chemicals were reduced to 1/10 (80 mg). Looking into the penalty points assigned to the LPME, six of ten points arose from acidification with formic acid (250 µg per sample). But this we can reduce from six to one penalty point by using citric acid – then we are down to five penalty points, and if we use soybean oil as liquid membrane rather than dihexyl ether, we are down to four - and most probably this is the greenest we can do it. If we think similar with LC-MS, and reduce penalty points to four by making the mobile phase greener, our total score is 92…
Current laboratory leaders are probably not concerned about eco-scale scores of 59 or 92, but I am very sure that those in the same position in year 2050 – they are currently 15 years old school kids, by the way – they will make decisions based on such numbers because sustainability will have VERY high priority in the future. In year 2050, no laboratories can survive without offering analytical services with excellent eco-scale score. Thus, we need to develop the concepts, technologies, and forefront applications for this, and this is one reason why (our) microextraction research is important. The second reason, I have explained previously, is because many chemicals will be measured in the future with smartphones – these have to be combined with sample prep – in small (micro) scale of course…
Eco-Scale assessment – look into Trends in Analytical Chemistry 37 (2012) 61-71