Size exclusion chromatography sample preparation

Given the variety of explosives, it is no surprise that chromatography is central to their analysis. Techniques that are or have been used include TLC, GC, HPLC, ion chromatography, CE, MEKC, supercritical fluid extraction, and size exclusion chromatography. Samples can be prepared for chromatographic analysis with simple solvents using water, acetone, and the like. SPME is also used to preconcentrate samples, particularly when the explosives must be extracted from an aqueous environment. SPME can be adapted to HPLC to avoid thermal degradation issues that commonly arise in explosives. Another approach is to derivatize the explosives directly on the fiber such that the derived substance can be analyzed by means of GC. ... 

A variety of procedures were utilized to analyze this reaction mixture and to characterize a,10-diaminopolystyrene. Thin layer chromatographic analysis using toluene as eluent exhibited three spots with Rf values of 0.85, 0.09, and 0.05 which corresponded to polystyrene, poly(styryl)amine and a,w-diaminopolystyrene (see Figure 1). Pure samples of each of these products were obtained by silica gel column Chromatography of the crude reaction mixture initially using toluene as eluent [for polystyrene and poly(styryl)amine] followed by a methanol/toluene mixture (5/100 v/v) for the diamine. Size-exclusion chromatography could not be used to characterize the diamine since no peak was observed for this material, apparently because of the complication of physical adsorption to the column packing material. Therefore, the dibenzoyl derivative (eq. 5) was prepared and used for most of the analytical characterizations. 

A reliable procedure for determination of molecular parameters number, weight and z-averages of the molecular weight (Mj, i = n, w and z respectively) for polyethylenes, PE, by means of Size Exclusion Chromatography, SEC, has been developed. The Waters Sci. Ltd. GPC/LC Model 150C was used at 135 C with trichlorobenzene, TCB, as a solvent. The standard samples as well as commercial stabilized and not stabilized PE-resins were evaluated. The effects of sampling, method of solution preparation, addition of antioxidant(s), thermal and shear degradation were studied. The adopted procedure allows reproducible determination of and M , with a random error of 4% and M2, with 9%, within 2 to 72 hrs from the initial moment of preparation of solutions. 

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