Styragel columns

Narrow-bore columns are most useful for the analysis of polymers that are difficult to analyze in inexpensive solvents. However, if the appropriate equipment is available, good results can be obtained for a broad range of standard analyses. A comparison of an analysis of standards between an equivalent bank of conventional 7.8-mm and solvent efficient 4.6-mm columns is shown in Fig. 11.4. The columns used were Styragel HR 0.5, 1, 2, and 3 columns at 35°C with tetrahydrofuran (THF) as the solvent. The flow rate was 1 ml/min for the conventional columns (Fig. 11.4A) and 0.35 ml/min for the solvent-efficient 4.6-mm columns (Fig. 11.4B). If the correct equipment is available, the reduced solvent consumption of these solvent-efficient Styragel columns is of value to the environmentally conscious user. 

FIGURE 11.4 Comparison of chromatograms obtained on conventional (A) and solvent-efficient Styragel columns (B). In each case the column bank was a bank of Styragel HR 0.5, HR I, HR 2, and HR 3 columns at 3S°C with THF as the solvent. The sample is a mixture of polystyrene standards. With proper care and optimized instrumentation, good resolution can be obtained with solvent-efficient Styragel columns. (Courtesy of Waters Corp.)... 

Styragel columns are available not only in a broad range of pore sizes, but they are also shipped in three different solvents. See Section III,A,5 for more details. 

It is especially important to note that Styragel HT columns can be purchased in three different solvents. Conversion procedures for these columns to most of the other commonly used SEC solvents are available in the care and use manual of the Styragel HT column line. Although the same conversion procedures are suitable for other Styragel columns as well, the column stability of... 

Styragel columns can be used in a wide range of organic solvents. Elution protocols have been worked out for all polymers that are soluble in organic... 

Styragel columns are compatible with most solvents commonly used in size exclusion chromatography. Exceptions are found on both sides of the polarity scale the use of standard general-purpose Styragel columns with aliphatic hydrocarbons or with alcohols (except hexafluoroisopropanol) and water is generally not recommended. However, it is possible to pack columns in special solvents for special-purpose applications. The interested user should contact Waters for additional information. 

Styragel columns can be used with a broad range of solvents and at elevated temperature. They can be converted to different solvents and temperatures following the general guidelines given in this section. Detailed conversion protocols are available in the care and use manual. 

Solvent selection and conversion chart for Waters Styragel columns. (Courtesy of... 

Waters Styragel Column, Care and Use Manual, Waters Milford MA 01757, brochure 044491TP, Revision 1, Mareh 1994. 

Gel Permeation Chromatography. The instrument used for GPC analysis was a Waters Associates Model ALC - 201 gel permeation chromatograph equipped with a R401 differential refractometer. For population density determination, polystyrene powder was dissolved in tetrahydrofuran (THF), 75 mg of polystyrene to SO ml THF. Three y -styragel columns of 10, 10, 10 A were used. Effluent flow rate was set at 2.2 ml/min. Total cumulative molar concentration and population density distribution of polymeric species were obtained from the observed chromatogram using the computer program developed by Timm and Rachow (16). 

In this study, four Styragel columns were utilized one column had a nominal porosity rating of 10, two colvtmns of 10, and the fourth column of 10 A. The refractometer was maintained at 37°C. A 5 ml syphon was used to monitor a solvent flow rate of 1 ml/min. The instrviment was run at the highest sensitivity setting because the refractive index difference between our solvent and polymer was only moderate and because a number of samples analyzed had a broad molecular weight distribution (MWD). 

Figure II). GPC curves (in CH2CI2, at 25°C, flow rate ImL/min., using I0JA y styragel column).

Gel permeation chromatography (GPC) was carried out on a Waters 720 GPC instrument using a methylene chloride eluant and a series of Micro-styragel columns of 10,000, 1000, 500, and 100A pore sizes. Reported values were standardized against polystyrene. 

Molecular weights were determined using a Waters high-pressure GPC instrument (Model 6000 A pymp, a series of five p-Styragel columns (10s, 10s, 10, 103, 500 A), Differential Refractometer 2401 and UV Absorbance Detector Model (440) and a calibration curve made by well fractionated polyisobutylene standards. 

Number-average molar masses were determined using a vapor pressure osmometer (VPO) (Hitachi 117 Molecular Weight Apparatus) at 54.8 0.1°C in toluene (Fisher Scientific, certified A.C.S.) which was distilled from freshly crushed CaH2. The VPO apparatus was calibrated with pentaerythritol tetrastearate (Pressure Chemical). Gel permeation chromatographic (GPC) analyses were performed in tetrahydrofuran by HPLC (Perkin-Elmer 601 HPLC) using six y-Styragel columns (106, 105, 10l, 103, 500, and 100 A) after calibration with standard polystyrene samples. 

Gel permeation chromatographic measurements were performed oj a Waters Associates HPLC with i-Styragel columns (10, 10, 10, and 500ANG) in chloroform with a polystyrene calibration. 

Figure 1. Calibration curve for four -styragel columns CPS in TCB at 135 °C).

The chromatograph Is Interfaced with a Digital LSl-11 microprocessor. Calibration, though requiring observations of chromatograms for monomeric and polymeric standards, can be efficiently achieved. Research over several years shows that styragel/micro-styragel columns are very stable under continuous utilization. 

High Molecular Weight Polymers in Cyclohexane and also in Special Column Arrangements. Waters Associates Ana-Prep and 501 GPC were used. One four-foot Styragel column of 5x10 pore size was connected to a pump and a differential refractometer detector to determine the effect of fritted discs on degradation. 

It is clear that the packed Styragel column is responsible for the degradation of the polymer. In all cases the pores of the packing are sufficiently large to accommodate portions of the... 

The separation of coal liquids by gel permeation chromatography using lOOA Styragel columns and solvents such as THF and toluene has been reported elsewhere (7.8.9.13.14). Coal liquids and petroleum crude are similar in their physical appearance as well as the complexity in composition. The major difference between the two is that petroleum crude does not contain oxygenated compounds, such as alkylated phenols, in substantial quantity. In addition, the average linear molecular size of petroleum derived asphaltenes (15.16) is much larger than that of coal derived asphaltenes (. ... 

The viscometer assembly is placed in the constant temperature column compartment of the chromatograph between the column outlet and the refractometer. A combination of two Waters Associates M-45 hydraulic filters in series with a capillary tubing coil (length 10 ft., I.D. 0.01 in.) is used to dampen the line pressure fluctuations caused by the pump. With the above pressure damping modifications the overall system noise was reduced to less than 1 millibar at 1.0 ml/min flow rate in tetrahydrofuran (THF) for a set of six p-Styragel columns 10 ,... 

To implement this technique a combination of two p-styragel columns with 100A and 500A porosity was used. A sample size of 50jjji of 0.1 (W/V) standard narrow distribution polystyrene with M = 1.8 X 10 was injected on to the columns. THF was used as the mobile phase at a flow rate of 1 ml/min and temperature of 50 C. Using the data analysis routine described above, a value of 115pA was obtained for AV as shown in Figure 9. 

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