Polystyrenes elution volume

This simply relates to how linear the relationship between the peak molecular weight of narrow polystyrene standards versus elution volume fits a straight line. This is typically measured with the linear correlation coefficient, r. ... 

Traditionally, column efficiency or plate counts in column chromatography were used to quantify how well a column was performing. This does not tell the entire story for GPC, however, because the ability of a column set to separate peaks is dependent on the molecular weight of the molecules one is trying to separate. We, therefore, chose both column efficiency and a parameter that we simply refer to as D a, where Di is the slope of the relationship between the log of the molecular weight of the narrow molecular weight polystyrene standards and the elution volume, and tris simply the band-broadening parameter (4), i.e., the square root of the peak variance. 

The most widely used molecular weight characterization method has been GPC, which separates compounds based on hydrodynamic volume. State-of-the-art GPC instruments are equipped with a concentration detector (e.g., differential refractometer, UV, and/or IR) in combination with viscosity or light scattering. A viscosity detector provides in-line solution viscosity data at each elution volume, which in combination with a concentration measurement can be converted to specific viscosity. Since the polymer concentration at each elution volume is quite dilute, the specific viscosity is considered a reasonable approximation for the dilute solution s intrinsic viscosity. The plot of log[r]]M versus elution volume (where [) ] is the intrinsic viscosity) provides a universal calibration curve from which absolute molecular weights of a variety of polymers can be obtained. Unfortunately, many reported analyses for phenolic oligomers and resins are simply based on polystyrene standards and only provide relative molecular weights instead of absolute numbers. 

Particle separation can be characterized by the separation factor, Rp, which is the ratio of eluant to particle elution volumes, or, by the difference in elution voliame, AV, between particle and eluant marker turbidity peaks. For polystyrene monodisperse standards, a linear relationship occ irs between the log of the particle diameter and AV, with a series of parallel lines resulting for different concentration of either salt or surfactant below its critical micelle concentration (IT>18,19) The separation factor has also been shown to be independent of eluant... 

The elution volumes of polystyrene and benzene in the size-exclusion mode were 0.98 and 1.78 ml, respectively (Figure 1.4A). This means that separations by molecular size can be achieved between 0.98 and 1.78 ml in this system. In the normal phase mode the elution volumes of octylbenzene and benzene were 1.98 and 2.08 ml, respectively, in n-hexane solution (Figure 1.4B). This type of chromatography is called adsorption or non-aqueous reversed-phase liquid chromatography. These are adsorption liquid chromatography and non-aqueous reversed-phase liquid chromatography. The elution order of the alkylbenzenes in the reversed-phase mode using acetonitrile was reversed... 

Non-Aqueous SEC Evaluation. The SEC calibration report for a peak position method using a series of narrow MWD polystyrene standards is shown in Table I, As can be seen, a linear fit produces a high correlation to the data (r=0.9997). Figure 1 displays the molecular weight calibration plot of elution volume versus log molecular weight for the series of polystyrene standards. 

The mean elution volume and total variance calculated from the e qperimental chromatograms of polystyrene and 1,2-polybutadiene on the ARL 9 0 GPC instrument are so listed in Table I. The coefficients of the effective relation, coordinates of the cross-point, paranrater % and spreading factor were computed by the schema outlined above. The results obtained are listed in Table II and III, The effective relations and calibration... 

First, we estimated the parameters a to be 0.01 and 8 to be 0.05. For the estimation of the standard deviation of the DP values, twenty chromatograms of NBS 706 polystyrene were measured and elution volumes at the distinguished per cent points of the integral curve of each chromatogram were calculated. Then, the value a was obtained to be 0.042 mL. The value 6 was estimated to be 0.1 mL, which corresponds to 0.3 % of the elution volume at the center of the calibration curve of this SEC system and 5 % difference of molecular weight. 

Figure 4 to that In Figure 5. Our computer software has been modified to allow for these changes by using the elution time of cyclic trlmer as a measure of flow rate for a given run. The system Is calibrated by using polystyrene spiked with cyclic trlmer. For each run, elution volumes are normalized on the basis of cyclic trlmer elution. This technique assumes constant flow rate during each run and compensates for run-to-run variations. ...

The DVB-linked MA polymers showed evidence of "kill" polystyrene and block copolymer arm with peak elution volumes at the same position as in the LB chromatograms. Note that in Figure 2b, the LALLS chromatogram has a shoulder on the major peak which is not observable in the DRl chromatogram this corresponds to a sign change in the slope of the log M(v) vs. v relationship. 

The universal calibration approach ([n]. M vs elution volume) for polystyrene standards and narrow molecular triacetate fractions show slight deviation from linearity. This departure from linearity has been attributed to differences in both hydrodynamic behavior and the Mark-Houwink exponent a for the two polymers in question. 

Universal Calibration. A function of the hydrodynamic volume [r ] M was plotted against the elution volumes of cellulose triacetate fractions and polystyrene standards run in dichloromethane have all indicated slight deviation from linearity as shown in Figure 2. 

Calibration of Gel Permeation Chromatograph Polystyrene Calibration. A plot of molecular size in (S) versus elution volume for polysty-rene standards in dichloromethane showed deviation from linearity at about 2,200 which may be attributed to Imperfect column resolution, peak broadening, axial dispersion and skewing. The extensive tailing of the chromatograms of high molecular weight polystyrene standards observed in dichloromethane has also been reported in the literature (23-26). 

Universal Calibration. Plots of [q] M against elution volumes indicate that polystyrene and cellulose triacetate follow different calibrations as shown in Figure 2. This deviation from linearity may be due to the following reasons. 

FIGURE 3.17 Three-dimensional plot of scattering intensity as a function of scattering angle and elution volume for a broad molecular weight distribution (MWD) polystyrene (PS) (NITS standard reference 706). (Courtesy of Wyatt Technology Corporation, Santa Barbara, CA 93117 wyatt wyatt.com. With permission.)... 

Fig. 2. Effect of the uv detector noise on the estimation of the molecular weight as function of elution volume for a narrow polystyrene standard. The symbols represent molecular weights obtained using the universal calibration and viscosity measurements on collected fractions...

Our primary calibration curve obtained with narrow MWD linear polystyrene samples could now be used to determine the molecular weight distribution of branched PVAc (B ) by means of eqs. (39), (40) and (17). The calibration curve for branched PVAc was not linear but showed a slight upturn at the low elution volume range as shown in Fig. 9. The calibration curve in Fig. 9 could be represented by... 

Two series of narrow MWD polystyrene standards were used to calibrate a SN-01A GPC equipment, one of which (TSK) was supplied by Toyo Soda Co. and the other (NFS) was prepared and characterized in this laboratory. The column (3x1 M) were packed with NDG porous silica beads. Tetrahydrofurane was used as eluent. The elution volume was counted by a 2.60 ml. siphone tube. 

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