Is 3D printing a good alternative to prepare novel devices for Green Analytical sample preparation?

Green Chemistry can be defined as the design of processes that reduce or eliminate hazardous substances and are described by the 12 Principles of Green Chemistry (PGCs). The PGCs provides a guide of the green characteristics that a chemical process should fulfill. However, the evaluation is complicated without an adequate metric that provides the possibility to convert the characteristics of the method to an objective scale level, such as a number or a color. For this purpose, green metrics have been developed in order to do a comprehensive evaluation of the method greenness. The older systems were based on atomic efficiency or mass of generated waste, but those are not adequate for all the chemistry branches, especially on Analytical Chemistry. Hence, a series of novel metrics, such as National Environmental Methods Index, Eco-Scale, Green Analytical Procedure Index, RGB model, Hexagon or Analytical GREEnness metric approach has appeared. Regarding Analytical Chemistry, especially in the sample preparation field, a novel trend based on the use of 3D printing devices has emerged. The different 3D printing modes offer the possibility to prepare devoted devices that affects the miniaturization, automation, reduction of solvents and can be prepared in short times with low energy. Therefore, 3D printing could offer novel alternatives in the preparation of Green Analytical Chemistry methods. In this work, the six mentioned metrics were used to evaluate the greenness of 11 published works that perform sample preparation using 3D printed devices. The results of each metric have been discussed and a comparison of all metrics has been done. The most adequate methodology for the evaluation was the Analytical GREEnness metric approach which was used to compare the greenness level of one of the selected works with a work using more conventional materials and systems. These results demonstrate the capabilities of 3D printing to help in the development of novel Green Analytical Chemistry methods.