Off-line optimization of the separation of 2,4-dinitrophenylhydrazones by gas chromatography using chemometric techniques

An off-line optimization technique based on soft modeling methods has been used to determine the optimum conditions for the separation of eight carbonyl-2,4-dinitrophenylhydrazones by gas chromatography equipped with a nitrogen-phosphorous detector. In this method theoretical simulations of peak retention time and peak width at base-line are coupled to a factorial design to map the chromatographic response surface. The calculated retention times from isothermal data have been used to calculate the chromatographic parameters. A full 3³ factorial design was used to locate the optimum conditions for the temperature program, utilizing initial oven temperature, T_i, the programming rate for the first ramp, PR₁, and the programming rate for the second ramp, PR₂ as independent variables. The optimum conditions obtained for these parameters were: T_i, 140 °C; PR₁, 12 °C min^-1; PR₂, 8 °C min ^-1. The maximum analysis times achieved by this optimum was 10.6 min.