Recent Advancements on Greening Analytical Separation

Abstract

60–80% of the analysis time for a significant number of analytical methods is taken up by the preparation, treatment, and separation of individual sample components, and most of the chemicals and solvents involved in the analysis are consumed in this step. We will demonstrate that many emerging methods of analytical separation science can meet the requirements of green chemistry by reducing the use of solvents and other reagents, lowering energy consumption by increasing the speed of analysis, and by miniaturizing and making equipment portable. Although recent efforts to make high performance liquid chromatography greener are praiseworthy, capillary electrophoresis, which comprises a group of separation methods that use narrow-bore fused-silica capillaries, is especially promising. It is highly competitive with liquid chromatography, which is the biggest consumer of organic solvents in analytical chemistry. However, capillary electrophoresis has not received the recognition it deserves as a green separation method that consumes microscopic volumes of solvent. It is a technique that is sufficiently mature to promote the greening of analytical chemistry via miniaturization—the most auspicious development in contemporary analytical chemistry. In this review, we will discuss recent developments in greening chromatography, and demonstrate the potential of electrophoresis and microfluidics in this regard.

Keywords:

• chromatography
• supercritical fluids
• electrophoresis
• microfluidics
• green chemistry

Notes

¹To view green chromatography from a wider green philosophical perspective it is interesting to consider the work of K. Rebane, an Estonian physicist. He writes that history indicates that the species and societies that act more quickly and consume more high-quality energy and materials are the “winners”: in other words, those that cause more pollution and promote the faster growth of entropy. This could be a reason why protection of the environment is inherently difficult and why it is almost impossible to significantly reduce man's consumption of energy and materials in a competitive world. To escape this inevitably fatal evolutionary outcome, fundamentally different thinking is needed—thinking which makes the survival of mankind the foremost value. A completely green process could be one in which pollution is transported away from Earth as infrared radiation. Karl K. Rebane, Energy, entropy, environment: why is protection of the environment objectively difficult?”, Ecological Economics, 13, 2, 89–92, (Rebane, 1995).

²He et al., 2007, provide a definition of the terms “in-situ” and “on site.” In this chapter, on-site analysis is understood to be a common analysis procedure that involves sample collection/preparation using a field-portable instrument. In-situ analysis leaves the sample site virtually undisturbed. In-situ analysis could be done with an x-ray spectrometer but it is difficult to imagine how a chromatographic analysis of art or soil samples would be possible.

³Although arguments in favor of the benefits to society may not move a chromatographer who is wrestling with everyday problems of maintaining his/her research in a competitive level, the political-economic situation in a particular country may persuade scientists to accept green solutions. The authors have personal experience in this regard. The rise of CE at the beginning of the 1990s coincided with the political changes in Eastern Europe that caused a dramatic reduction in funding for fundamental research. In this situation it was almost impossible to use HPLC due to the lack of supplies and the requirement for large amounts of solvents and spare parts. On the other hand, it was relatively easy to assemble CE instruments from old color television sets (which contained a high voltage power supply) and modify the cells of discarded optical HPLC detectors and thereby carry on research at a reasonably competitive level.