Chemistry Reference
In-Depth Information
What are the expectations of Green Analytical Chemistry for CE? The method was very actively studied at
the beginning of the 1990s, but its development has lost momentum in recent years. More than 2000 papers
on fundamental studies in CE have been published each year of the last decade. Nevertheless, the industry has
been slow to accept the method. CE is struggling to replace HPLC for the analysis of conventional small
molecule pharmaceuticals. A certain amount of avoidance can be explained by the lack of familiarity with CE
among analysts in general, which can lead to the development of methods that are not robust, perform poorly
and give CE a negative reputation. Analytical chemists have learned that CE is highly sensitive to parameter
changes and that it is not a very reproducible technique, but modern instrumentation has eliminated most of
the early variability issues. As robust interfaces with mass spectrometers are developed, the obstacle of the
incompatibility of CE with MS will soon be overcome [23].
As we already pointed out, CE has received little recognition as a genuinely green separation method
despite the fact that the solvents it employs are usually harmless aqueous buffers
1
. As the ACN shortage
continues to influence the field of analytical separations, CE is gathering increased attention, as confirmed in
the report from one panel discussion [13]. Suppliers of CE equipment have responded to the need for improved
robustness and reliability. They have made improvements in newer equipment. There is also a trend towards
well-monitored and validated chemistry/capillary kits to improve performance, for example, for inorganic
anion and metal ion determinations. The emergence of more powerful, automated instruments makes this
technique more accessible than ever. There are some signs that the future of CE is bright. It is probable [13]
that the use of CE for small inorganic anion and metal ion analyses will replace ion-exchange chromatography.
Chiral analysis by CE is well established. The method is also used for screening and characterizing compounds
(determination of
pKa
, solubility, etc.). Dedicated equipment and related kits/capillaries will be available for
specific protein characterization/assays. CE is far superior to either SDS-PAGE or IEF gels. However, CE
should not completely replace HPLC. It is a technique that is complementary and orthogonal to HPLC.
Proponents of CE believe that outdated thinking on the part of separation scientists is the biggest obstacle to
acceptance of the technique. As highlighted by the forum cited above, [13] the method still needs the support
of instrument manufacturers to build better and more robust instrumentation, of vendors of consumables to
continue to devise kits and reagents, and of scientists themselves to develop novel methodologies and
applications. Without this type of investment, the technique cannot expand, but without expansion, no one
wants to invest. Wider acceptance of green chemistry by analysts may help to break this impasse.
9.2.3
CE as a method of choice for portable instruments
In addition to its small consumption of chemicals, another overlooked quality of CE is its potential for
portability, via miniaturization of all its components. Portability is believed to be an important and obvious
feature of green analytical instruments. Portable instruments are considered to be more economical than their
stationary counterparts. They consume fewer resources (either power or chemical) and generate less waste.
Moreover, they are designed to be taken to the site of the analysis, that is, a point-of-care (POC) such as a
hospital, home or crime scene. The portability of an instrument is generally understood to be its ability to
1
Although arguments in favour of greenness for the benefit of mankind may seem too philosophical for a chromatographer who wrestles
with everyday problems, 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 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 its requirement for large amounts of solvents and spare parts. On the other hand, it was relatively easy to
assemble CE instruments from old colour television sets (which contained a high voltage power supply) and to modify the cells of
discarded optical HPLC detectors an thereby carrying on research at a reasonably competitive level.
