Small molecules applications, generally

The most important application of semi-permeable membranes is in separations based on reverse osmosis. These membranes generally have pores smaller than 1 nm. The pressure across the semi-permeable membranes for reverse osmosis is generally much larger than those for ultrafiltration, for example. This is because reverse osmosis is usually used for small molecules which have a much higher osmotic pressure, because of the higher number density, than the colloids separated in ultrafiltration. As a result reverse osmosis membranes have to be much more robust than ultrafiltration membranes. Since the focus of our discussion in this chapter will be on reverse osmosis based separations, we will describe these membranes in greater detail. 

General theories of molecular structure have been advocated by different groups in the past but their applicability has been restricted to the shape, Le. bond lengths and bond angles, of small molecules. Two types of approaches deserve special mention ... 

Noncovalent interactions such as van der Waals, hydrogen bonding, n-n stacking and electrostatic interactions have been widely used to hybridize pristine nanocarbons via ex situ approaches. The major advantage of this route is that the nanocarbons do not require modification prior to hybridization and their structure remains undisturbed, an important factor in many electronic applications. The strength of hybridization is weaker compared to covalent interactions but the synthetic process is generally simpler. Noncovalent attachment of small molecules to nanocarbons is often used to change the surface chemistry for subsequent ex situ or in situ hybridization. 

While LIF monitoring is established in other manufacturing industries, it is relatively new within the pharmaceutical industry. The application of real-time intrinsic LIF for the manufacture of pharmaceuticals in general can be broken in to three areas (i) classic (small molecule) final drug product manufacturing (ii) biopharmaceutical prodnct manufacturing and (iii) factory operational applications. 

Carraher and Williams showed that for many polymers, differences in symmetry and band production were similar for small molecules as they were for the same groups found in polymers. Thus, observations from the literature and in model-compound studies are generally applicable to similar moieties present in polymeric systems for both Raman and IR spectral analyses. 

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