Environmentally benign analytical

The development of analytical chemistry conhnues at a steady rate and every new discovery in chemistry, physics, molecular biology, and materials science finds a place in analytical chemistry as well. The place can either be a new tool for existing measurement challenges or a new challenge to develop stable and reliable methods. Two examples are the advent of nanostructure materials and alternative solvents, both of which saw their main development in the past decade. Nanostructural materials pose a new scale of measurement challenge in size and number. New solvents with their environmentally benign properties offer a possibility for wasteless operation. 

X-ray fluorescence,1516 surface acoustic waves (SAW) for determining volatile organic compounds (VOCs),17 18 and immunoassays19-21 are examples of direct analytical techniques (in which a sample preparation step is unnecessary) that are environmentally friendly. In addition, there are environmentally benign procedures from which reagents and solvents have been eliminated or their quantities minimized (calculated per analytical cycle) ... 

The following sections discuss recent advances in green analytical chemistry in the context of the whole analytical process, that is, from sample collection, sample preparation, to sample analysis, as well as the characteristics of some traditional methodologies that have always been environmentally benign but were never described as green. ... 

In addition, other techniques, in which quantities of reagents and solvents per one analytical cycle are limited, are part of environmentally benign procedures. These include... 

At the present time, the scientific society needs the development of new environment-friendly analytical methods. Thns, chemists are snpposed to develop analytical methods that are free from the nse of hazardous reagents and leave minimal amonnt of chemical waste. Snrfactants play an important role in onr everyday life becanse they are applied in honseholds as well as in many indnstrial processes. Most snrfactants are snsceptible to biodegradation, metabolic, and other breakdown reactions that may lead to metabolites with significant environmentally benign chemical properties. Generally, most snrfactants appear to be less toxic in the environment than wonld be inferred from laboratory tests. The quantities of each... 

Even though the extraction efficiency for some analytes can be increased by change of extraction fluid, carbon dioxide is by far the most common compound used (98% of all applications). It has low critical parameters, it is nonexplosive, nontoxic, and environmentally benign. Alternatives have been proposed such as alkanes and freons but they have never been widely accepted due to health and safety risks for the former and ozone depletion by the latter. One of the few competitors to carbon dioxide is nitrous oxide, however, it might cause explosion in contact with high amounts of organic material. Supercritical carbon dioxide has a polarity similar to that of n-hexane, and consequently for the extraction of more polar analytes an organic modifier such as methanol or acetonitrile (1-5%) has to be added to increase the polarity (see the section Modifiers ). To maintain supercriticality for two-component fluids, somewhat different conditions have to be applied, but normally there is no problem at the conditions under which SFE is normally carried out. 

From an environmental point of view, a substantial decrease in CO2 emissions would follow the replacement of propylene with a propane feedstock, considering the overall process ca. five times higher in the propylene process than for propane). In this way, a recent study on the evaluation of the environmental impact by a systematic analytical method comparing the current commercial process from propylene with a hypothetical propane process (assuming in both a yield to acrylic acid close to 90%, currently obtained with the propene process) concluded that the propane process implied a decrease of 20% in the environmental impact of the industrial process. Moreover, a yield to acrylic acid higher than 61% was calculated to be enough for the propane process to be more enviromnentally benign. 

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