Oligomer column

Samples of AOT were eluted in THF on Toyo Soda Oligomer Columns at 118 ml/hr. A single rather narrow peak was observed for sample sizes from 0.1 to 31 mg. The dependence of... 

Chromatograms of the ethanol-soluble fraction were obtained in THF on Toyo Soda Oligomer columns over a range of sample masses, as shown in Figure 5 The exclusion limit of these columns is 50,000 and Mp" values above 10,000 are inaccurate because the calibration curve is very steep in this region. Consequently, chromatograms were also obtained on the "Main Column" GPC with the results shown in Figure 6. 

Figure 1. Separation of epoxy cresol Novolac oligomers. Columns Perkin-Elmer/PL gel 10-fim 100 A and 10-pm 1000 A.

Extraction Butanoneln-hexane Oligomers, column extraction 1159... 

The value for the heat of fusion of PPS, extrapolated to a hypothetical 100% crystalline state, is not agreed upon in the literature. Reported values range from approximately 80 J/g (19 cal/g) (36,96,101) to 146 J/g (35 cal/g) (102), with one intermediate value of 105 J/g (25 cal/g) (20). The lower value, 80 J/g, was originally measured by thermal analysis and then correlated with a measure of crystallinity deterrnined by x-ray diffraction (36). The value of 146 J/g was deterrnined independendy on uniaxiaHy oriented PPS film samples by thermal analysis, density measurement via density-gradient column, and the use of a calculated density for 100% crystalline PPS to arrive at a heat of fusion for 100% crystalline PPS (102). The value of 105 J/g was obtained by measuring the heats of fusion of weU-characterized linear oligomers of PPS and extrapolation to infinite molecular weight. 

Cyclopentadiene oligomers up to octamers can be effectively analy2ed and quantified by supercritical fluid chromatography using a chemically bonded methyl siUcone capillary column. 

Figure 4.25 (page 122) shows results obtained on TSK-GEL SW and TSK-GEL PW columns for low molecular weight polyethylene glycol (PEG) oligomers and high molecular weight dextrans. The TSK-GEL G2000PW column successfully resolved components of PEG 200, whereas the TSK-GEL G2000SW column did not (Fig. 4.25A). Therefore, the TSK-GEL G2000PW column would be preferable for this analysis.

Figure 6.3 shows a comparison of elution patterns of standard polystyrene between a linear-type column and a standard-type column. Because of the high linearity of its calibration curve, the linear series has improved the efficiency of oligomer domain separation. 

The performances of column set A1 and B are similar, although column set B is more expensive. Using a specially selected column set for oligomer... 

Figure 9.7 shows separations under identical conditions using PSS SDV columns with 3 (Fig. 9.7a)-, 5 (Fig. 9.7b)- and 10 (Fig. 9.7c)-/i,m particle size columns. A polystyrene oligomer standard was injected and all analyses were performed in THF as the eluent. The much higher efficiencies of small particle size columns are obvious, which is important in the SEC separation of low molecular weight compounds such as additives, by-products, and resins. The reader should note that all chromatograms are area normalized and have the same Y axis to show the differences in peak width and height. 

Figure 13.22 shows the resolution of the surfactants Tween 80 and SPAN. The high resolution obtained will even allow the individual unreacted ethylene oxide oligomers to be monitored. Figure 13.23 details the resolution of many species in both new and aged cooking oil. Perhaps the most unique high resolution low molecular weight SEC separation we have been able to obtain is shown in Fig. 13.24. Using 1,2,4-trichlorobenzene as the mobile phase at 145°C with a six column 500-A set in series, we were able to resolve Cg, C, Cy, Cg, C9, Cio, and so on hydrocarbons, a separation by size of only a methylene group. Individual ethylene groups were at least partially resolved out to Cjg. This type of separation should be ideal for complex wax analysis.

As a final example of column durability and solvent resistance in small pore gels we were able to resolve nylon 6 oligomers using a methanol mobile phase and 205-nm UV detection as shown in Figure 13.29. In fact, polar solvents such as acetone, acetonitrile, methanol, and 2-propanol, are used routinely as needed with no ill effects. 

FIGURE 13.25 Using chloroform as the solvent, a mixture of polystyrene standards were nicely separated on the 3-m set of columns. Run times here were 160 min. Plate count for toluene was calculated at 240,000 plates. The 500 MW Standard is separated nicely into its oligomers. 

There are different reasons to discard a column a column can be damaged by irreversible adsorption of reactive polymer samples. Small amounts of styrene oligomers are known to permanently elute from styrene-divinylbenzene materials with tetrahydrofuran as the eluent, which means a continuous shear degradation of the separation material and consequently a decrease of the packing quality this observation is very important if fractions are collected and used for further analyses, e.g., for the determination of infrared (IR) spectra. One can presume that similar effects are present with other organic materials too. 

PMMA). Under these conditions, some inevitable peaks are observed in the low molar mass range. This area starts for an elution volume of Mpmma of about 600. Enclosing a further column for this low molecular size range generally improves the separation, but the elution sequence of oligomer and disturbing peaks remains constant. 

Figure 2. Chromatogram on a PA 100 column of the 2-aminopyridine-labeled oligomers from the EPG-resistant fragments after de-xylosylation with HF at -12 °C.

Fraction 3 from the HW-55 S column was further separated by gel filtration on an HW-40 S column (Figure 4) to search for the smallest xylogalacturonan fragment and to remove the purely GalA oligomers. 

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