Ultrastyragel columns calibration

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. 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). 

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... 

The polymerization of trimethylene carbonate (1,3-dioxan-2-one) with a complexation catalyst was studied by Kriecheldorf et al. " On the basis of GPC measurements employing a universal calibration, weightaverage molecular weights up to approximately 22,000 were found. A combination of four Ultrastyragel columns was used, with nominal pore sizes of 100, 500, 1000, and 10,000 A. The detector was a Waters M410 differential refractometer. The... 

Molecular weights were determined by gel permeation chromatography (GPC) using a Waters HPLC system equipped with noodel 510 pump. Waters model 717 autosampler, model 410 refractive index detector, and model T-50/T-60 detector from Viscotek Corporation with 500, 10, 10 and 10 A ultrastyragel columns in series. Trisec GPC software version 3 was used for calculations. Chloroform was used as the eluent at a flow rate of 1.0 mL per minute. Sanq>le concentrations of 0.2 % wt/vol and injection volumes of 100 )XL were used. Molecular weights were determined based on a conventional calibration curve generate by narrow molecular weight polystyrene standards obtained from Aldrich chemical conq>any. 

Microspheres were monitored by scanning electron microscopy (SEM JEOL 35C), and their diameters were determined from the corresponding SEM microphotographs. Typically, ca. 500 particles in randomly sampled areas of microsphere specimens were analyzed. Molecular weight of poly(L-Lc) was determined by GPC. A system consisting of a LKB 2150 pump, Ultrastyragel 1,000, 500, 100, 100 columns, and Wyatt Optilab 903 interferometric refractometer was used for the measurements. GPC traces were analyzed by using calibration with narrow polydispersity < 1.15)... 

FIGURE 5-37. Calibration curve for some low-molecular-weight pharmaceutical compounds. Column 100 A Ultrastyragel 7.8 mm ID x 60 cm (two columns). (Reprinted from reference 9 with permission.)... 

A Waters GPC 150 CV, equipped with the DRI prototype 4 and a single capillary viscometer, was used for this study. A low-angle laser lightscattering (LALLS) detector (Chromatix CMX 100) was inserted between the column set and the GPC 150 CV detectors. Tetrahydrofuran (THF) was used at 40 °C and at a flow rate of 1 mL/mn. THF was filtered on a Millipore membrane-type FH and stabilized by lonol at a concentration of 0.04%. The columns used were a set of Waters Ultrastyragel (103—106 A). The narrow standards used for calibration were a set of polystyrene standards... 

The analyses were performed on a Polymer Lab apparatus, equipped with five ultraStyragel Waters columns (in the order 1000, 500, 10000,100, and 100000 A pore size) attached in series, using a Polymer Lab differential reffactometer. The solvent was THF or CHCI3, the flow rate was 1 mL/min, and 60 microliters of polymeric solution (15 mg/ml) were injected. Normally 50 fractions of 0.2 mL were collected. In the case of sanq)le M30, four different fractionation experiments were performed, and 50 fractions of 0.2 mL, 25 fractions of 0.4 mL, 15 fractions of 0.8 mL, 15 fractions of 1 mL were collected The chromatogram was calibrated using the result of the analysis of MALDI-TOF spectra of selected fractions (see Tables 1 and 2). The average molar masses (Mn and Mw) of the copolymer were measured using the Cahber software distributed by Polymer Lab. The type of calibration selected by us was a narrow standards the calibration function was polynomial of order 1 and the calculation method was area based. ... 

In order to standardize the GPC column set (ULTRASTYRAGEL), polystyrene standards and five selected polysilane samples were available. As the latter were not true monodisperse standards, calibration procedures were based on the molecular weights corresponding to the tops of he GPC peaks (Mp). 

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