GPC - Gel Permeation Chromatography
Analytical technique description
Gel Permeation Chromatography GPC (or Size Exclusion Chromatography SEC) is a very used analytical technique for the relative measurement of the molecular weight of polymers. A polymer solution is separated by a chromatographic column. Retention time gives medium molecular weight, while peak width gives molecular weights distribution.
It is a very common analytical technique for the determination of average molecular weight and molecular weights distribution of polymers. These are basic requisites in order to evaluate the performance of polymers to be used in conservation of any kind of material (stones, metals, glasses, etc.). Solubility in solvents, good applicability, easy penetration in substrate pores and good adhesion to substrate are strictly bound to molecular dimensions.
It is a method of separation, in which the sample solution is eluted through a chromatographic column that separates the molecules according to their size; they are then carried to a refractive index detector, which gives back a chromatogram: a dedicated software analyze it using as reference a specifically prepared calibration curve. That is because this is a relative method for molecular weight determination: there is a connection between the measured function and the concentration of the polymer in solution. Such correlation depends on interactions between polymer and solvent, between polymer molecules, etc., so the measured function remains valid just for that given polymer in that given solvent.
Instrumental details
HPLC-SEC Perkin Elmer system, model Series 200, equipped with a refractive index detector LC-30 (Florence Unit).
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