Journal of Chromatography A, 1002 (2003) 169–178 www.elsevier.com / locate / chroma Quantitative gas chromatography–olfactometry. Analytical characteristics of a panel of judges using a simple quantitative scale as gas chromatography detector * ´ Vicente Ferreira , Jan Pet’ka, Margarita Aznar, Juan Cacho Department of Analytical Chemistry, Faculty of Sciences, University of Zaragoza, 50009 Zaragoza, Spain Received 3 February 2003; received in revised form 11 April 2003; accepted 24 April 2003 Abstract Some questions related to the ability of gas chromatography–olfactometry (GC–O) to provide quantitative measurements of the concentration of a given odorant in an extract are explored and discussed. A panel of eight individuals has been used to evaluate the intensity of 15 odorants present at different concentrations. The use of very simple scales, such as a 0–3 scale, makes it possible to build calibration graphs based on the different stimulus–response models (Fechner, Stevens, Hill) and, with a proper calibration, up to nine different concentration levels can be discriminated by an eight-judge panel. The signal shows a good long-term stability, and its precision varies between 3.7 and 8% of the whole scale, with 5.7% as average. Sensitivity is extremely dependent on the compound: in the best case a concentration change of 20% can be detected, while in the worst, concentrations must differ more than one order of magnitude. In average, concentrations must differ between 2 and 4.7 times (including calibration error) or between 1.2 and 2.3 (excluding calibration error). The performance of the different judges, the effect of the close elution of two odors and the benefits derived from the use of more complex scales (7-points) are briefly discussed from the perspective of the analytical performance of GC–O methods.  2003 Elsevier Science B.V. All rights reserved. Keywords: Olfactometry; Calibration; Aroma analysis 1. Introduction al physical detectors, initially restricted their field of application to qualitative analysis. Its mission in this The human nose has been used as a gas chroma- context was to allow differentiation between those tography (GC) detector almost since the introduction volatile components with a scent, from those that do of GC, as the human nose is the most appropriate not have one. Nevertheless, in the last few years a detector to monitor the presence of an odorant in the series of studies has appeared in which different effluent of a gas chromatograph [1]. GC–O strategies are applied to the evaluation of the The individual characteristics of this detector, importance of one or several odorants in one or completely different from those from the convention- several samples, which is clearly a quantitative measurement [2–11]. These studies have had a repercussion in the industry of the aroma, as it is *Corresponding author. Tel.: 134-976-762-067; fax: 134-976- demonstrated by the increasingly greater supply of 761-292. E-mail address: vferre@posta.unizar.es (V. Ferreira). commercial equipment and prototypes designed to 0021-9673 / 03 / $ – see front matter  2003 Elsevier Science B.V. All rights reserved. doi:10.1016 / S0021-9673(03)00738-6