Chemistry Reference
In-Depth Information
enantiomeric separation. It was concluded that, when evaluated on a process level, Prep-HPLC requires 26
more resources than the Prep-SFC due to its inherent highest use of organic solvents. However, when evaluated
on a larger system boundary and quantifying the Cumulative Exergy Extracted from the Natural Environment
to deliver all mass and energy flows to the process level system boundary via the overall industrial metabolism,
it becomes clear that Prep-SFC requires 34
%
more resources than Prep-HPLC. It is partially due to the high
resource requirements related to the production of liquid carbon dioxide. This study illustrates the possibility
and advantages of quantifying both, energy and material resource intake, for industrial processes, being
exergy analysis: the unique, scientifically sound tool that enables researchers to quantify all kind of resources
and products on the same scale and to take into account all the resources for a proper evaluation.
Another technique that is gaining popularity for the quality control of raw materials and finished products,
especially in the pharmaceutical sector, is the ion mobility spectrometry (IMS). IMS is a gas-phase
electrophoretic separation technique in which the ion separation is carried out in the millisecond scale on the
basis of the different time required for an ion to transverse a region filled with inert drift gas under the
influence of an homogenous electric field. At the beginning IMS was only applied to the detection of
explosives [30], illegal drugs [31] and chemical warfare agents [32]. Pharmaceutical applications of IMS
have been reviewed by O'Donnell
et al
. [33] and they include the determination of pharmaceutically active
compounds [34, 35] and cleaning verification of the manufacturing equipment [36, 37].
So, it can be concluded that Green Analytical Chemistry enhances laboratory productivity, reduces the
environmental risks and provides economic opportunities in the analysis of raw materials and finished products.
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23.3 Process control
Recently, a growing number of researchers have focused their efforts in developing methodologies for the
monitoring of chemical production processes. The main reasons supporting those developments are (1) the
better quality of products required by the consumer, (2) more stringent regulations by the authorities in
relation to production and production processes; and (3) greater economic competition, which requires a
minimization of energy consumption, a reduction in the amount of raw materials used in reactions and process
operations and a decrease in the generated wastes and emissions. The term which defines this research area
is process analytical chemistry (PAC). PAC plays a very important role in the management of industrial
processes, in refining of raw materials and minerals, in agriculture, in food and animal feedstuff manufacturing,
in fertilizer processing and in the clinical and pharmaceutical field [38]. The principles of PAC are focused
on the advantages of generating immediate analytical data to correct process deviations and eliminating the
wait for the analytical response necessary to estimate the process status. In the traditional off-line approaches,
samples are taken from the reactor, transported to the analytical laboratory, analyzed and evaluated and
corrective actions are taken if required (time-delayed monitoring). Modern PAC promotes at-line, on-line or
in-line process control, where samples are measured close to or inside the reactor or process chain and the
corrective action can be taken in near or real time (real time monitoring).
In 2003, about 85
of chemical production processes were analyzed off-line [39], using analytical methods
such as HPLC. The main disadvantages of those methodologies are the long time of analysis, the time delayed
response and the associated costs of solvent consumption and waste generation. The off-line/at-line control
is often used in cases in which the number of analysis is reduced and the sample preparation for their analysis
is difficult to automate. However, the economic environment of the past few years has provoked a tendency
amongst enterprises to move towards a high as possible degree of control over production processes in order
to reduce costs and increase product quality. Moreover, governmental organizations, such as the FDA, are
forcing several industries (the pharmaceutical industry is a good example of this) to implement process
analytical tools. The process analytical technology (PAT) initiative, promotes the use of techniques that
enable the monitoring of critical process parameters during pharmaceutical manufacturing [40]. Currently,
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