Calibration using polystyrene

Vapor Pressure Osmometry - The number average molecular weights of polymers with Mn < 20,000 were determined using "Model 232A Molecular Weight Apparatus, Wescan Instruments, Inc., 3018 Scott Blvd., Santa Clara, CA 95050". Toluene was used as solvent and the instrument was calibrated using polystyrene of Mn 9,000 and 20,400. 

Molecular weights of the copolymers were determined by gel permeation chromatography (GPC) with four p-styragel (Haters) columns calibrated using polystyrene standards. Chloroform was used as the eluate at a flow rate 1.5 ml/min. An LKB-2140 Ultraviolet Photodiode Array detector was used to detect the polymer with a scan range from 190 to 370 nm. 

The function can then be interpolated for particle sizes between those corresponding to the known latices. The relationship between particle diameter and y, the mean elution volume of the particles, is the particle size versus elution volume calibration. As discussed earlier, an HDC is calibrated using polystyrene latices, but the calibration is valid for other latices (23), and even nonlatex materials. (Colloidal gold that had been sized at 40 nm by electron microscopy was detected at 39 nm using the FlowSizer.)... 

GPC was used as a major tool to determine molecular size distributions of asphalts and their fractions. However, one must bear in mind that data obtained by GPC do not represent actual, absolute, molecular weight values of asphalt compounds since the system has been calibrated using polystyrene standards. Besides, it is known that factors such as the adsorption of polar compounds on the gel and/or intermolecular associations of polar compounds can affect GPC results. Each factor affects the results in a different way. Adsorption on the gel would result in lower apparent molecular size values, while the association of these compounds would cause earlier elution, giving apparent molecular size values higher than the actual values. The effect of intermolecular associations in asphalts on GPC data, even at concentrations usually considered low enough to destroy all solute-solute associations, has been reported in the literature (22, 23). 

Molecular weights were obtained by GPC in dichloromethane (1 mL/min) using a Waters pump model 6000, an injector (Rheodyne) and a refractive index detector (RID-6A Shimadzu), equipped with a PL gel 5)iim mixed-C linear column. The system was calibrated using polystyrene standards with low polydispersity. 

The molecular weight distribution was determined by gel permeation chromatography (GPC) using a Waters 510 pump with refractive index detector. The separation was performed using two columns in series Styragel HR 4 and HRl with 5 pm particle diameter. THE was used as the eluent at a flow rate of 1 ml/min. The biooil samples were dissolved in THE at a concentration of 2 g/1. The GPC columns were calibrated using polystyrene standards of 400, 600, 760, 800, 1200, 2000, 2430 and 20700 molecular weights. 

Molecular weight distributions of polysilanes, determined by gel permeation chromatography (GPC), are frequently bimodal as shown in the example in Figure 7. The numerical values are calibrated using polystyrene standards, so the molecular weights... 

The system was calibrated using polystyrene sulphonates (PSS) (Polysciences, NJ, USA). 1 gL standards were prepared (35, 18, 8, 4.6 kDa). Blue Dextran, a high molecular weight polysaccharide (approx. 2 000 kDa) and an acetone solution (1%) were used to determine the column s void volume and total permeation volumes, respectively. The PSS s were detected at 224 nm (see Figure 4.7), the acetone at 280 nm and the Blue Dextran at 260 nm. All samples were detected well inside the 15 min/sample run time. 

Figure 6. Applicability of calibration using polystyrenes and IGEPALS for aromatic hydrocarbons, acids, and naphthalenes, see Experimental for a description of the compounds.

The IR spectra of the samples were recorded on Perkin-EImer 621 and Nicolet MX-IE spectrometers which were calibrated using polystyrene and CO2 bands, respectively. 

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