Multivariate optimization of a gas chromatographic method for the determination of organic impurities in ethanol

Medicinal ethanol obtained from alcoholic fermentation drags traces of organic impurities that have adverse effects in human health. For this reason, it is a priority to carry out a thorough examination of its composition before the final consumption. The identification of these compounds was performed by a gas chromatographic technique which was focused in the reduction of the applied temperatures, and in the minimization of gas consumption, by means of an experimental optimization of the parameters. The effect of six chromatographic parameters was studied over three desired responses. The four factors that did not influence the responses were the injector temperature, the FID temperature, sample injection volume and the hydrogen flow rate. As a consequence, the latter variables were set in their most conservative intervals considering the long life of the spare parts of the gas chromatograph. On the other hand, the starting run temperature and the linear velocity of the carrier gas were optimized to the final values of 49.16 degrees C and 35.00 cm/s, respectively, achieving a reduction of the run time from 34.96 to 21.38 min, without loss in the resolution between the first two peaks from 1.190 to 1.131. Moreover, the width of the last analyte peak significantly decreased from 0.310 to 0.212 min, and the signal/noise ratio was enhanced, hence improving the quantification of the analytes.