Evaluation of a calibration marker scheme for open tubular column gas chromatography with on-column injection and electron-capture detection

Abstract

A new method of calibration for open tubular column gas chromatography with electron-capture detection is proposed. A homologous series of n-alkyl bromides is added to each sample analyzed to provide simultaneously a retention index scale and a method of solute calibration. The detector response to equimolar amounts of n-alkyl bromides is constant, permitting a calibration curve to be generated for each sample by adding a series of n-alkyl bromides arranged in increasing stepwise molar concentrations. Each solute is then treatd as if it were an imaginary n-alkyl bromide of some concentration obtained from the experiment and converted to an actual concentration from the relationship between the solute and n-alkyl bromide calibration curves, stored in the computer memory. It is shown that for the complete chromatographic system, temperature-programmed retention indices can be reproduced with an average standard deviation of ca. 0.35 index units and that the relative error for the calibration melthod is similar to that obtained by daily solute calibration. The advantages of the new method are that it combines the operation of solute identification by retention index values and multiple solute calibration into a single method, capable of automation. Compared to standard calibration procedures, it is less time-consuming and subject to fewer operator errors.