Size-exclusion chromatography calibration curves

Fig. 5-5. Size exclusion chromatography calibration curves, plots of elution volume versus molecular weight for a series of macroporous polystyrene materials designed for reversed phase chromatography and as base matrices for subsequent modification. Calibration performed using a 300 mm x 7.5 mm ID column and polystyrene standards with a tetra-hydrofuran eluent.

Calibration curve for the determination of formula weight by size-exclusion chromatography. 

A new direct method for using size exclusion chromatography (SEC) to evaluate polymer intrinsic viscosity [n] is discussed. Sample viscosity information is obtained by combining SEC elution curve data and calibration data using direct SEC-[n] calibration procedures without involving polymer molecular weight calculations. The practical utility, convenience and the expected precision of the proposed method are illustrated. 

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. 

Since size exclusion chromatography separates polymer molecules by their size (especially hydrodynamic size), plotting the molecular size vs. the retention volume should be universal, regardless of the polymer molecular weight. The universal calibration curve is given as ... 

Briefly describe how SEC (size exclusion chromatography) separates polymers according to size. Explain how the universal calibration curve can be used to determine molecular weight. 

Universal calibration curve for size exclusion chromatography. Data points are polybutadienes in tetrahydrofuran at 25 °C in crosslinked polystyrene columns. There is a reasonably linear region of the calibration curve spanning the data (solid line) but the linear region has its limits (dotted curves). 

Stogiou, M. Kapetanaki, C. latrou, H. Examination of the universality of the calibration curve of size exclusion chromatography by using polymers having complex macromolecular architectures. Int. J. Polym. Anal. Charact. 2002, 7, 273-283. 

The rightmost term on the right side of the equation can be seen as the selectivity in size-exclusion chromatography. It is the inverse of the slope of the dimensionless form of the calibration curve multiplied by the fraction of the column occupied by pores. It should be maximized by selecting the best pore size and pore size distribution for the molecular-weight range of the analyte. 

Resolution in size-exclusion chromatography is a function of both the calibration curve and column performance. To normalize resolution to a molecular-wei t difference of a decade, the specific resolution has been defined as... 

In tile technique of liquid chromatography at the critical condition (LCCC), macromolecules of different sizes are eluted at the same time (Figure 10.19). ° This peculiar elution behavior is achieved making use of columns in which the macromolecules are at the adsorption-elution transition, and Figure 10.19 reports the calibration curve for LCCC along with the curves for adsorption and size exclusion chromatography, respectively. ... 

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