High-pressure size exclusion chromatography

Novolac molecular weights were measured in THF at 35°C by high pressure size exclusion chromatography using a Waters Model 510 pump (flow rate=1.0 ml/min), 401 differential viscometer detector and a set of Dupont PSM 60 silanized columns. A universal calibration curve was obtained with a kit of 10 narrow molecular weight distribution, linear polystyrene standards from Toya Soda Company. Data acquisition and analysis were performed on an AT T 6312 computer using ASYST Unical 3.02 software supplied with the Viscotek instrument. 

Note Ultrafiltration was used to fractionate the DOM prior to fulvic acid isolation, and the size was determined by high-pressure size exclusion chromatography. The middle and large size fractions had molecular weights corresponding to a range of 1260 to 1470 amu (atomic mass units), and those in the small size fraction had molecular weights of about 1000 amu. 

O Loughlin, E. and Chin, Y. P., Effect of detector wavelength on the determination of the molecular weight of humic substances by high pressure size exclusion chromatography. Water Res., 35, 333-338, 2000. 

Zhou, Q., S. E. Cabaniss, and P. A. Maurice. 2000. Considerations in the use of high-pressure size exclusion chromatography (HPSEC) for determining molecular weights of aquatic humic substances. Water Research 34, no. 14 3505-3514. doi 10.1016/80043-1354(00)00115-9. 

Muller, D. Ndoume-Nze, M. Jozefonvicz, J. High-pressure size-exclusion chromatography of anticoagulant materials, J.Chrornatogr., 1984, 297, 351-358. 

Silica gel was the first stationary phase to be used effectively at high pressures for exclusion chromatography. Silica gel is mechanically strong and, as already discussed, can be made available with a wide range of pore sizes. It is particularly useful in the separation of... 

Fish and Komlenic (1984) and Fish et al. (1984) employed size exclusion chromatography-high-pressure liquid chromatography (SEC-HPLC) with element detection to determine the molecular weight distribution of metal-bearing compounds in four heavy petroleums. The observed... 

SEC-HPIjC size-exclusion chromatography/high-pressure... 

The reaction products were analyzed chromatographically [high pressure liquid chromatography (HPLC) and size exclusion chromatography (SEC)] and spectroscopically [proton nuclear magnetic resonance ( H NMR) and secondary ion mass spectrometry (SIMS)]. 

Figure 3 Reversed-phase chromatography of products after alkaline hydrolysis of /3-poly(L-malate), Discrete polymer products are formed, which differ in length by several units of L-malate. The absorbance at 220-nm wavelength was measured, (a) /3-Poly(L-malate) before hydrolysis, (b) After 10-min incubation in 20 mM NaOH at 37°C. (c) After 15 h in 20 mM NaOH at 37°C. (d) After I h in 500 mM NaOH at 100°C. High pressure chromatography (HPLC) on Waters reversed-phase Ci8- i-Bondapak. The methanol gradient (in water-trifluoro acetic acid, pH 3.0) was programmed as follows 0-40 min 0.3-23%, 40-47 min 23-40%, 47-49 min 40%, 49-54 min 40-0%. (d) Inset size exclusion chromatography after 3-min alkaline hydrolysis at pH 10.2. BioSil SEC 250 column of 300 mm x 7.8 mm size, 0.2 M potassium phosphate buffer pH 7.0.

There are two types of stationary phases commonly used in exclusion chromatography silica gel and micro-reticulated cross-linked polystyrene gels. A third type of exclusion media is comprised of the Dextran gels. Dextran gels are produced by the action of certain bacteria on a sucrose substrate. They consist of framework of glucose units that can form a gel in aqueous solvents that have size exclusion properties. Unfortunately the gels are mechanically weak and thus, cannot tolerate the high pressures necessary for HPLC and, as a consequence, are of very limited use to the analyst. 

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