Temperature programmed retention indices: Calculation from isothermal data. Part 1: Theory

Abstract

SummaryDirect conversion of isothermal to temperature programmed indices is not possible. In this work it is shown that linear temperature programmed retention indices can only be calculated from isothermal retention data if the temperature dependence of both the distribution coefficients and the column dead time are taken into account.Procedures are described which allow calculation of retention temperatures and from these, accurate programmed retention indices. Within certain limits the initial oven temperature and programming rate can be chosen freely.The prerequisite forthis calculation is the availability of reliable isothermal retention data (retention times, retention factors, relative retention times, or retention indices) at two different temperatures for one column.The use of compiled isothermal retention indices at twodifferent temperatures for the calculation of retention temperatures and thus temperature programmed indices is demonstrated. For the column for which programmed retention indices have to be determined, the isothermal retention times of the n-alkanes and the column dead time as a function of temperature have to be known in addition to the compiled data for a given stationary phase.Once the programmed retention indices have been calculated for a given column the concept allows the calculation of temperature programmed indices for columns with different specifications. The characteristics which can be varied are: column length, column inner diameter, phase-ratio, initial oven temperature, and programming rate.

The Volatile Compounds of the Elderflowers Extract and the Essential Oil

“…These identifications were accomplished by comparison of retention times with authentic samples or by comparison of their relative retention index (RRI) to a series of nalkanes [9].…”

Preparation, evaluation, and comparison of wide bore (320 μm) and narrow bore (50 μm) cyanosilicone‐coated capillary columns for gas chromatography

“…This and some other effects of slightly different experimental conditions may cause much confusion when comparing polarity and quality of polar columns within and between laboratories. A detailed analysis of the effects of column tength, film thickness, phase ratio, column diameter, initial temperature, and programming rate on programmed retention indices for apolar phases can be found elsewhere [16,17].…”

Prediction of GC retention values under various column temperature conditions from temperature programmed data

“…This approach can be applied to multi-ramping temperature programs for column temperature and/or programs for inlet pressure of carrier gas. Wright et al [14] and Gerbino et al [15] predicted the retention values both in single-column and serially linked capillary column systems in TPGC through the equation suggested by Curvers [2]. Besides the work described above there are many publications discussing prediction of retention time and calculation or transformation of retention index in TPGC.…”

“…The methods suggested by Curvers [2] and by Akporhonor [3] have commonly been applied up to now. Garcia et al [12] predicted and compared retention times, retention indices and retention temperatures of various polar solutes on four packed columns coated with unequally polar stationary phases by using seven different methods.…”