Size exclusion chromatography equipment

Figure 2.2 Typical setup of size-exclusion chromatography equipped with triple detection for determination of the moiecuiar weight of polymers without the need for prerequisite calibration. DRi, differential refractive index detector DV, differentiai viscometer I, injector MALS, multi-angle light-scattering detector (depending on the model, the scattered light is measured at 3 or 18 different angles) P, pump. The central unit includes a computer and software.

Size exclusion chromatography (SEC) separates molecules of a polymer sample on the basis of hydrodynamic volume. When the chromatograph is equipped only with a concentration-sensitive detector, i.e. conventional SEC, a molecular weight distribution (MWD) can be obtained from the chromatogram only through use of a calibration function relating molecular weight and elution volume V (2). 

Figure 5 shows the separation of the plasticiser components present in a PVC-based cling film. The sample was first dissolved in tetrahydrofuran and then the components present separated by size exclusion chromatography (SEC) using mixed bed-E columns (Polymer Laboratories) and tetrahydrofuran eluting solvent. IR spectra of the separated components were then obtained using "LC-Transform " (Lab Connections) equipment. Components as they elute from... 

Figure 5 Separation of the plasticisers present in PVC cling film by size exclusion chromatography. (Peaks left to right, identified by their infrared spectra, obtained using LC-Transform equipment, as DEHA, ESBO and PVC.)...

Molecular weight measurements were determined by size exclusion chromatography on a high pressure liquid chromatograph equipped with a differential refracto-meter. A Waters Styragel HR 5 i column set (106 104 500 A) was employed and calibrated with PS standards. THF was used as solvent at a flow rate of 1 ml/min. 

The conformational mobility of a chromophoric main-chain polymer is often connected to its electronic structure. Therefore, changes in the UV-visible absorption spectra and/or chiroptical properties are spectroscopically observable as thermo-, solvato-, piezo-, or electrochromisms. It is widely reported that o-conjugating polysilanes exhibit these phenomena remarkably clearly.34 However, their structural origins were controversial until recently, since limited information was available on the correlation between the conformational properties of the main chain, electronic state, and (chir)optical characteristics. In 1996, we reported that in various polysilanes in tetrahydrofuran (THF) at 30°C, the main-chain peak intensity per silicon repeat unit, e (Si repeat unit)-1 dm3 cm-1, increases exponentially as the viscosity index, a, increases.41 Although conventional viscometric measurements often requires a wide range of low-dispersity molecular-weight polymer samples, a size exclusion chromatography (SEC) machine equipped with a viscometric detector can afford... 

Instrumentation. A Pharmacia BioPilot Column Chromatography system was used to perform large-scale size exclusion chromatography (SEC) with an 11.3 x 90 cm BioProcess column packed with Sephacryl S-200 HR gel. High performance size exclusion (HPSEC) and ion exchange chromatography (HPIEC) were conducted with Pharmacia Superose 6 and 12 (HR 10/30) and Mono-Q (HR 5/5) columns respectively, equipped with Beckman model 520 system controller and Beckman model HOB HPLC pumps. 

High Performance Size Exclusion Chromatography (HPSEC) A Varian Model 5000 liquid chromatograph equipped with a variable wavelength UV detector, two columns in series (PL gel, 300 x7.5 mm, particle size 5/im, porosity of 50 and 500A), was used, THF being the eluent. 

Additional reagents and equipment for dialysis or size-exclusion chromatography... 

A way out of the dilemma is the determination of the molecular size distribution of the chromatographable organic carbon (COC) as it is offered from size exclusion chromatography (SEC) equipped with an organic carbon (OC) detection system. 

Procedure (See Chromatography, Appendix IIA.) Use a liquid chromatograph suitable for size-exclusion chromatography and equipped with a refractive index detector and a 60-cm x 7.5-mm (id) column packed with 5-p.m, 500A porosity PL-Gel, or equivalent, both operated at 40°. Operate the chromatograph at 500 to 1500 psi at a flow rate of 1.0 mL/min. 

H and Si NMR spectra were recorded on a Brnker Avance 300 spectrometer respectively at 300.13 and 75.6MHz at room temperatnre. CDClj and toluene were used as solvents. For Si NMR, Cr(acac)3 (0.03 M) was added in the tube and a delay between pulses of 20 s was set. IR spectra were recorded on a Perkin-Ehner IR ET 1760-X. The average molecnlar weight of the linear polymers was determined by size exclusion chromatography in TFIF (flow rate l.OmL.min" ) on an apparatus equipped with a Waters refractive index detector, a Waters column pack (Ultrastyra-gel 10, 10 100 A) and a Minidawn Wyatt light scattering detector. 

IR, UV, and H NMR spectra were obtained using Jasco FTIR-410, Shimadzu UV-2400PC, and Jeol JNM-GX270 (270 MHz) spectrometers, respectively. Size exclusion chromatography (SEC) was carried out on a Jasco GPC equipment consisting of a PU-980 pump, an RI-930, and a Shodex KF-806M column with polystyrene as a standard and tetrahydrofliran (THF) as an... 

Size exclusion chromatography in the main uses conventional liquid chromatographic equipment. In most cases the polymer in solution can be injected directly onto the chromatograph, however in the case of formulated polymers which contain inorganic fillers and pigments some prior sample separation will be needed. 

Size Exclusion Chromatography. Exclusion chromatography was carried out on an apparatus comprised of a Minipump (Milton Roy), a model 7012 injector (Rheodyne) equipped with a 100-pl loop, an R401 differential refractometer (Waters), and a Model 153 UV detector, X,=254 nm (Altex). A Superose-6 column (30 cm x 1 cm OD)(Pharmacia) was eluted at 0.53 ml/min.. Column efficiency, determined with D2O, was at least 12,000 plates/meter. 

TLC is a good technique to use when normal-phase solvents provide optimum separation. Typical thin-layer separations are performed on glass plates that are coated with a thin layer of stationary phase. The stationary phases used in TLC encompass all modes of chromatography including adsorption, normal- and reverse-phase, ion-exchange, and size-exclusion." The equipment required is simple and inexpensive. TLC is an ideal technique for the isolation of compounds because of its simplicity. However, for TLC to be successful, the impurity and/or degradant level should be at or above 1%. Any component present below this level is very difficult to isolate on a TLC plate because of higher detection limits. 

General. Commercially available polyimides were used (see Table I). Solvents were reagent grade or better and were used as received. 1-Methylpiperazine (Aldrich Chemical Co.) was > 99.9% pure. Lactic acid (Aldrich) was reduced to 50% by weight in water and refluxed for an hour to hydrolyze esters. IR spectra were recorded on a Perkin-Elmer Model 1430 spectrometer. Thermogravimetric analysis was done on a P-E System 4/TGS-2 instrument. Size exclusion chromatography was done on a Perkin-Elmer Series 3B equipped with the LC-75 spectrophotometric detector. The column set used consisted of P-E 0258-2134, 2133, and 2131 columns (pore sizes 103, 104, and 106 A, respectively). For electrophoretic deposition experiments, a TCR Power Supply (Electronic Measurement Systems Inc.) was used. Temperatures are reported in °C throughout. 

Several techniques used in process analytical chemistry have not been discussed here. They are rather specialized, such as size exclusion chromatography, ion chromatography, atomic absorption, etc. Rather than employing commercially available equipment, most of these installations rely on heavily modified laboratory equipment adapted to the process analytical application. Again, the reader is referred to the Process Analytical Reviews [2] for complete details of these applications. 

The size exclusion chromatography, which is generally used as an analysis technique, can also serve to prepare samples by fractionation. However, this method, which will be studied in detail in Section 6, calls for rather heavy equipment which is not to be found in most laboratories, and the operation in itself is rather costly... 

The high salt concentrations used can present a challenge for the HPLC equipment. Pumps with seal-wash are prrferred. If chloride buffers are used, HPLC systems with nonmetallic fluid paths are recommended. It is also advisable to flush the salt solution out of the system when it is not in use. Temperature and pH can affect the separation and should therdbre be controlled. But both the temperature effect and pH effect are smaller than in other forms of chromatography (with the exception of size-exclusion chromatography). 

Size Exclusion Chromatography (SEC) is widely used technique polymer characterization. The standard configuration of a SEC apparatus consists of three parts (/-5), viz., a solvent-delivery system (equipped widi an injection port), the columns, and a differential refractive index (RI) detector. This basic configuration can be modified by adding an additional detector, either in series or in parallel to the RI detector (J-5). The second detector can be a viscometer (2), a concentration detector (3), an UV detector (4) or a Light Scattering (LS) device (5),... 

Hi h Pressure Liquid Chromatography. Size exclusion chromatography was performed isocratically in 0.2 M ammonium acetate (flow-1.5 ml/min) with a Water s Model 840 HPLC with a Toyo-Soda G2000SWXL column (30 cm x 7.8 mm). Eluting components were monitored in the UV at 214 nm and by fluorescence (Ex - 230 nm, Em - 300 nm) and collected in 4 minute fractions for bioassay. Reverse phase chromatography was conducted with a Hewlett-Packard Model 1090 HPLC equipped with a Vydac C-18 column using a linear gradient over one hr from 10% to 50% acetonitrile in 0.1% TFA. Sample was monitored with a diode array detector from 190 to 350 nm in the UV. 

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