Retention program, aspects

The important aspect of programmed elution techniques with respect to optimization criteria is that the peak width does not increase with the retention time in a manner corresponding to eqn.(1.16). In programmed analysis a constant peak width is wanted throughout the chromatogram (see section 6.1). 

The second aspect of optimization in programmed analysis involves adapting the selectivity by variation of secondary parameters. The various secondary parameters listed in table 3.10 may be used to vary the selectivity of a chromatographic system without affecting retention to a great extent (see the discussion in section 3.6.1). 

The two experiments required to describe the isothermal retention vs. temperature relationships through eqn.(3.10) or eqn.(6.2), or the three required by eqn.(6.3), may either be performed isothermally or under programmed conditions. However, in the latter case the calculations to obtain the coefficients Ay B, and, if eqn.(6.3) is used, C, will be more complicated and more than two or three experiments may be required to estimate the coefficients with sufficient accuracy. The latter aspect suggests the use of an iterative interpretive method, in which the values of the coefficients are updated after each new experiment until the accuracy of the predicted optimum turns out to be sufficient. 

To illustrate the approach to the theory of retention and band broadening, we examine some aspects of programmed temperature gas chromatography. ... 

There are many books and other sources that discuss the retention index from theoretical and practical aspects. One comprehensive book is "The Sadtler Standard Gas Chromatography Retention Index Library" [15]. This series of book (from Volume 1 to Volvune 4) provides detailed data on the retention indices for more than 2,000 compoimds under varying isothermal and temperature programming GC conditions for the purpose of the general identification of unknown compoimds. 

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