Green metric for microwave-assisted sample preparation for elemental analysis: GreenPrep MW Score

Abstract

Rapidly moving to the 3^rd decade of the 21^st century, it is clear that our technologies must evolve to sustainable processes, not aggressive to the environment nor to all forms of life. Chemical sciences are going green and surely analytical chemistry is moving towards this same direction. But we need to speed up the pace. To evaluate an analytical procedure, we should be able to validate it. Nowadays, method validation is not only the demonstration that analytical results are accurate, in fact method validation is also related to green chemistry aspects. If we think about elemental analysis, we can state that the sample preparation step has been improved, nonetheless it certainly requires further improvements through the development of greener procedures. In this contribution, we propose a set of green metrics named GreenPrep MW Score for the evaluation of microwave-assisted sample preparation procedures using different technologies, either based on cavity microwave oven, or on a single reaction chamber system. The GreenPrep MW Score was proposed considering the whole analytical procedure and how chemical parameters, technology variables and workflow can be optimized, and how these factors impact green metrics score. The authors do not intend to substitute sound metrics already proposed for evaluating the sample preparation step. Our goal is to propose a complementary strategy which helps us identify specific points to be improved in microwave-assisted procedures. The application of the developed metric was demonstrated for several samples containing different matrices, such as foods, multivitamin tablets, spodumene; in addition, strategies for improving green chemistry aspects were discussed.