Chromatographic resolution and analysis accuracy can be seriously affected by broadening of very sharp bands associated with both high-performance size-exclusion chromatography and other liquid chromatography methods using less than 5 micron particles. The effect on column plate count by extra-column band broadening from injection systems, detectors, connectors and "guard" columns is discussed and exemplified with experimental data. The special cases of tailing and doublet peaks for a single species are investigated. These effects are eliminated by a special sample injection technique. Computer simulation studies demonstrated that serious errors can result from calculating column plate count with non-Gaussian peaks. The maximum allowable peak tailing is suggested and a new method for quantitating peak skew is proposed.
SynopsisThe method of Balke, Hamielec, LeClair, and Pearce for GPC calibration and molecular weight computation is reviewed and evaluated. A new method, called GPCVB, is proposed which uses the single broad molecular weight distribution (MWD) standard for calibration developed by those workers, but which also incorporates the chromatographic dispersion u to make the method more accurate in genera! use. Equations are presented for computing the relationship between actual MW and retention volume V R under the chromatographically broadened curves. This relationship is then compared to those obtained by using the Balke et al. method and the peak position method.
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