Strategies and considerations to green analytical separations: a review

Although analytical methodologies are known to generate pollution, universal strategies to decrease their environmental, safety, and health burdens while maintaining performance are lacking. Separation science techniques including sample preparations and chromatography require large amounts of solvent and power to separate, identify, and quantitate pure constituents from their matrices. Recent advancements to green analytical chemistry have now provided comprehensive metrics, such as the analytical method greenness score (AMGS), that allow researchers to better understand their method's environmental burden, compare it to other methods, and indicate what areas can be addressed to enhance sustainability. Here, we review approaches and technologies that can be used to green analytical separations with a focus on improving the method's analytical figures of merit. Approaches to green sample preparation are first considered including microextraction techniques in liquid, solid, and supercritical phases and the ability to automate such techniques. We focus on high-performance liquid chromatography and sub- or super-critical fluid chromatography, where it is shown that changing the column dimensions and packing can reduce environmental impact while preserving chromatographic resolution. We review equations to calculate the greenest flow rate at which to operate a separation method, then we discuss of modern ultrafast and high throughput separations. Finally, we describe digital signal processing for analytical signals as a major green technology for the first time. We observed that, using digital signal processing, an ultrafast liquid chromatographic separation of 101 components in just one minute produced an AMGS of 0.12 which is, to our best knowledge, the lowest ever reported.