Molecular Imprinted Polymer :History

ganden88 — Mon, 14 Aug 2006 11:32:52 +0000

The emergence of molecular imprinting has its original source in the area of immunology. By the early 1930s Breinl and Haurowitz, followed by Mudd, proposed a theory for the diversity of antibody formation in their encounter with xenobiotic antigens. The remarkable specificity of antibody-antigen complexes, found in, e.g. the chiral recognition of d- and l-tartranilic acid was attributed to the interactions of the chemical groupings of the nascent antibody with the antigen during antibody biosynthesis. Each structural unit of the antibody would be selected and oriented, at the moment of synthesis, to fit the local configuration and features of the antigen surface. These theoretical considerations were further elaborated by Pauling, who postulated that the great diversity in antibody formation was due to the formation of different three-dimensional configurations of the antibody polypeptide chain induced by the interaction with the antigens. Following these “instructive” theories on antibody diversity, the antibodies would be able to change their 3-D-structure in order to form as many interaction points as possible with the epitopes of the antigens. Thus, the antibody combining sites were “moulded” with the antigen as a template in a casting procedure, i.e. they were molecularly imprinted with the antigens (Figure 2).

Later, these theories were found to be incorrect and their instructive models abandoned in favour of the more appropriate “clonal selective” theory of antibody formation. Nevertheless, their models laid the foundations for the area of molecular imprinting.

Adopted from www.smi.tu-berlin.de

Solid phase microextraction

ganden88 — Sun, 13 Aug 2006 21:12:18 +0000

Solid phase microextraction, or SPME, is a sample preparation technique, used both in the laboratory and on-site, developed in the early 1990s at the University of Waterloo, by Dr. Pawliszyn’s group. It is an innovative simple and inexpensive technique, where the use of solvents is not necessary.

SPME is a fibre coated with an extracting phase, that can be a liquid (polymer) or a solid (sorbent), which extracts different kinds of analytes, from volatile to non-volatile, from different kinds of means, that can be in liquid or gas phase. The quantity of analyte extracted by the fibre is proportional to its concentration in the sample, as long as equilibrium is reached or, in case of short time pre-equilibrium, with help of convection or agitation. After extraction, SPME fibre is transferred to the injection port of separating instruments, like a Gas Chromatograph, where desorption of the analyte takes place and analysis is carried out.

Adopted from Wikipedia

WORLD OF MICROEXTRACTION

Molecular Imprinted Polymer :History

Solid phase microextraction