Preparative gel permeation

Cotmnercial cellulose triacetate samples were fractionated by both fractional precipitation and preparative gel permeation chromatography (GPC). The triacetate fractions were characterized by vlsco-metry, high speed membrane osmometry (HSMO) and GPC. A fair agreement has been found between the molecular weights of various triacetate fractions determined by the three procedures. 

Figure 1. Fractionation of birch lignosulfonates by preparative gel permeation chromatography.

The solubility difference between the starting materials and the end products in various solvents should be considered first. Column chromatography on silica gel or other column materials is usually used for the purification of the Pcs. In the case of more than one main end product, such as given in Fig. 5, preparative gel permeation chromatography will be efficient. 

Methyl-4-trimethylsiloxybutyl Phenyl Tellurium1 Into an argon-flushed, 50-ml flask fitted with a magnetic stirrer are placed 86 mg (1 mmol) of 2-methyltetrahydrofuran and 3 ml of dichloromethane. 3 mg (0.01 mmol) of zinc iodide and 375 mg (0.3 ml 1.35 mmol) of phenyl trimethylsilyl tellurium are added to the stirred solution at 20°. The mixture is stirred at 20° for 6 h, pyridine is then added, and the mixture is concentrated under vacuum at 20°. The residue is chromatographed on a short column of silica gel with chloroform as eluent. The chloroform is evaporated and the residue is rcchromatographed on a preparative gel-permeation column with chloroform as eluent yield 260 mg (71%) light-yellow oil. 

The first synthetic route explored to produce cydic polymers made use of ring-chain equilibrium. This approach involves the natural equilibrium that occurs between linear and cydic polymers during condensation polymerizations although, inevitably, this yields linear byproducts and broad polydispersities. As a result, precipitation or preparative gel-permeation chromatography (GPC) was required to obtain cyclic polymers of sufficient purity for further study. This approach is amenable to a broad range of polymerization chemistries, induding the preparation of cyclic polyesters [7,8], polyethers [9], poly(dibutyltin dicarboxylates) [10,11], and poly(siloxanes) [12-15]. 

Dodgson, K. Sympson, D. Semiyen, J. A., Studies of Cyclic and Linear Poly(dimethylsiloxanes) 2. Preparative Gel Permeation Chromatography. Polymer 1978,19,1285-1288. 

The coupling product was isolated by preparative gel permeation chromatography on Sephadex G-25. Characterization by NMR and elemental analysis indicated that up to 80 percent of the aldehydes could be substituted. 

Dodgson, K., Sympson, D., and Semiyen, J.A. (1978) Studies of cyclic and linear polyfdimethyl siloxanes) 2. Preparative gel permeation chromatography. Polymer, 19,1285-1289. 

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