Ultrastyragel columns

Gel permeation chromatography was performed in tetrahydrofuran using a Waters pump system and a Model 410 differential refractive index detector for the eluant. Five Ultrastyragel columns with nominal porosities ranging from 500 to 105 angstroms were used for all the samples and the polystyrene standards. 

Figure 3. Individual Ultrastyragel column calibration curves.

Determination of Pore Size Distributions. The shape and range of a GPC calibration curve are, in part, a reflection of the pore size distribution (PSD) of the column packing material. A consideration of the nature of PSDs for the ULTRASTYRAGEL columns to be used in this work is therefore appropriate. The classical techniques for the measurement of PSDs are mercury porisimetry and capillary condensation. The equipment required to perform these measurements is expensive to own and maintain and the experiments are tedious. In addition, it is not clear that these methods can be effectively applied to swellable gels such as the styrene-divinylbenzene copolymer used in ULTRASTYRAGEL columns. Both of the classical techniques are applied to dry solids, but a significant portion of the pore structure of the gel is collapsed in this state. For this reason, it would be desirable to find a way to determine the PSD from measurements taken on gels in the swollen state in which they are normally used, e.g. a conventional packed GPC column. 

Figure 1. Separation of BHA and BHT on a lOOA Ultrastyragel column using chloroform and tetrahydrofuran. Conditions ...

Figure 1. Typical calibration curves for lOOA, lO A Ultrastyragel columns.

Figure 5 Scheme for prediction (simulation) of the calibration curve for a column set consisting of two 500A and one lO A Ultrastyragel columns (see text for details). 

Figure 6. Plot on probability paper of cumulative PSD data for a 5OOA Ultrastyragel column. The mean (p = l.TO) and standard deviation (a= O.I2) of the Gaussian PSD were determined graphically.

In Figure 7, the predicted cumulative PSD is compared with the actual curve for the column set. It should be noted that the prediction is based on data from one 500A and one lO A ULTRASTYRAGEL column which had been calibrated in toluene. (Previous work (19,42) has demonstrated that equivalent PSDs are obtained with several eluents including chloroform, methylene chloride, THF, and toluene.) Neither of these columns was Included in the actual column set, which was independently calibrated in THF using a different instrument. Reasonably... 

Figure 9. Predicted and experimental cumulative PSDs for a column set consisting of one lOOA and one 103a Ultrastyragel columns (see legend).

Figure 11. Predicted (smooth curve) and experimental (boxes) cumulative PSD for a lO A Ultrastyragel column.

Figure 12. Predicted (smooth curve) cumulative PSD for a IO a Ultrastyragel column, determined incorrectly due to failure to convert log (MW) values to log 0. Experimental cumulative PSD (boxes) is shown for comparison.

SEC measurements with 500 S, lOA X and 10 K Ultrastyragel columns polymer concentrations were 3.5-5.5 mg/mL In samples Injected Into TCB at 0.5 mL/min flow rate. 

In this work, using ultrastyragel columns, it was found that instrumental broadening corrections were unnecessary. 

A gSe of two Waters ultrastyragel columns, designated 10 A and 10 A and a Waters pump (Model 590) for HPLC were used in this study. The elution solvent was tetrahydrofuran (THE) which was distilled in the presence of a small amount of CaH in order to remove the peroxide. The flow rate was maintained at 1 ml/min. The sample injection volume was -30 pi. The chromatogram detected by the differential refractometer (Waters R401) was recorded on a strip chart recorder. All experiments were performed at room temperatures with concentrations below the over-loading condition. 

GPC Analysis. Molecular weight characterizations were carried out using a Waters 840 Gel Permeation Chromatograph equipped with both an ultraviolet (UV) (Model 481) and a refractive index (RI) detector (Model 410). Two Ultrastyragel columns, in the running order of 1,000 and 10,OOOA pore... 

The molecular weight (Mw) and the molecular weight distribution (polydispersity Mw/M ) of the terpolymers were determined by gel-permeation chromatography with a Waters instrument equipped with UV and RI detectors and using Waters Ultrastyragel columns. The samples were measured at 30 °C in chloroform containing 0.1 vol % triethylamine as the mobile phase with a flow rate of 11/min. 

High-efficiency (> 4500 plates) GPC column. The following columns have been tested for this experiment a 7.8 mm ID x 30 cm 100-A juStyragel column and a 7.8 mm ID x 30 cm 100 A Ultrastyragel column. Other high-efficiency GPC columns (100 A or equivalent) should be suitable however, they have not been tested in this experiment. 

FIGURE 11-2. Separation of mixture of phthalates by GPC on a 100-A Ultrastyragel column. Analytical loadings are shown in (a) and preparative loadings are shown in (b). Mobile phase THF. Flow rate 1 mL/min. Detector UV at 254 nm, 0.5 AUFS in (a) and 2.0 AUFS in (fe) RI at X8 in (a) and X64 in (b). Sample dioctyl, dibutyl, and dimethyl phthalates with 50 /xL injection in (a) and 100-/xL injection in (b). (Note Actual separation will depend upon the quality of the mobile phase and column packing). 

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