Solvent usage

Solvents are substances that are liquid during application and will dissolve other substances, which can be recovered unchanged on removal of the solvent. Importantly, the solvents and the solutions involving them must be applicable for some purpose. Solvent systems must be understood before any rationale chemical process can be developed. 

Solvents are widely used by chemists. Educators in the physical sciences, especially chemistry, employ solvents in discussions of physical phenomena and in laboratory experiments. Industries around the world utilize the benefits of solvents to accomplish their desired goals. Individuals in all societies use solvents. In the face of these facts, it is imperative that the solvents used result in a minimal impact upon the environment. I list five true premises (Anastas and WUhamson, 1998)  

The goal of green chemistry is to reduce the hazards associated with products and processes that are essential not only to maintain the quality of life achieved by society through chemistry, but also to further advance the technical achievements of chemistry, and to do so in a sustainable manner. Reduction of risk is a beneficial result of green chemistry. Risk can be summarized in simple terms as the product of the hazard of a particular substance and the exposure to that substance  

A healthy approach to determining acceptable risk is to answer the following questions (Hughes, 1996)  

Green chemistry seeks to reduce or eliminate the risk associated with chemical activity by reducing or eliminating the hazard side of the risk equation, thereby obviating the need for exposure controls and, more importantly, preventing environmental 

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Though less important economically, solvent usage consumes a larger portion of the 1-nitropropane production than is consumed of the other nitroparaffins for this use. In particular, a blend of nitroethane and 1-nitropropane has been developed which is useful as an additive for improved coatings performance (116). 

The crosscurrent scheme is not generally economically attractive for large commercial processes because solvent usage is high and solute concentration in the combined extract is low. 

Recently, SPE cartridges and disks have been widely and successfully used in preconcentration processes [1-3]. They reduce solvent usage, disposal costs, and extraction time for sample preparation and obtain large enrichment factors. 

Substitution means the replacement of a hazardous material or process with an alternative which reduces or eliminates the hazard. Process designers, line managers, and plant technical staff should continually ask if less hazardous alternatives can be effectively substituted for all hazardous materials used in a manufacturing process. Examples of substitution in two categories are discussed—reaction chemistry and solvent usage. There are many other areas where opportunities for substitution of less hazardous materials can be found, for example, materials of construction, heat transfer media, insulation, and shipping containers. 

When investigating the suitability of a particular resin-bound separations process, the following factors are often important (i) resin consumption (ii) solvent usage (iii) productivity-chemical, optical and volume yields (iv) total number of separations steps and (v) capital costs. For any particular process, these factors differ in their relative importance. However, when evaluating a new separations method it is useful to examine each of these factors. The nonchromatographic separation method... 

Solvent usage is drastically reduced due to several factors. The feed can be flowed through the ChiraLig columns nearly continuously and high feed concentrations can be used as needed. Rapid loading occurs due to reasonable binding kinetics. The subsequent release (elution) step is accomplished in just a few bed volumes, with... 

Industrial analytical laboratories search for methodologies that allow high quality analysis with enhanced sensitivity, short overall analysis times through significant reductions in sample preparation, reduced cost per analysis through fewer man-hours per sample, reduced solvent usage and disposal costs, and minimisation of errors due to analyte loss and contamination during evaporation. The experience and criticism of analysts influence the economical aspects of analysis methods very substantially. 

Solvent usage Solvent for wetting and elution of analyte (10-20 mL) None... 

Miniaturisation of scientific instruments, following on from size reduction of electronic devices, has recently been hyped up in analytical chemistry (Tables 10.19 and 10.20). Typical examples of miniaturisation in sample preparation techniques are micro liquid-liquid extraction (in-vial extraction), ambient static headspace and disc cartridge SPE, solid-phase microextraction (SPME) and stir bar sorptive extraction (SBSE). A main driving force for miniaturisation is the possibility to use MS detection. Also, standard laboratory instrumentation such as GC, HPLC [88] and MS is being miniaturised. Miniaturisation of the LC system is compulsory, because the pressure to decrease solvent usage continues. Quite obviously, compact detectors, such as ECD, LIF, UV (and preferably also MS), are welcome. 

Another advantage of PTFE vessels is low adhesivity, which can help to reduce detergent and organic solvent usage during cleaning operations that would otherwise generate considerable effluent [6]. 

Figure 5.4 UK VOC emissions (1970-2002). Note the predominance of emissions from solvent usage in the latest data.

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