A lab-made electronic nose (Enose) with vacuum sampling and a sensor array, comprising
nine metal oxide semiconductor Figaro gas sensors, was tested for the quantitative analysis of
vapor–liquid equilibrium, described by Henry’s law, of aqueous solutions of organic compounds:
three alcohols (i.e., methanol, ethanol, and propanol) or three chemical compounds with different
functional groups (i.e., acetaldehyde, ethanol, and ethyl acetate). These solutions followed a fractional
factorial design to guarantee orthogonal concentrations. Acceptable predictive ridge regression
models were obtained for training, with RSEs lower than 7.9, R2 values greater than 0.95, slopes
varying between 0.84 and 1.00, and intercept values close to the theoretical value of zero. Similar
results were obtained for the test data set: RSEs lower than 8.0, R2 values greater than 0.96, slopes
varying between 0.72 and 1.10, and some intercepts equal to the theoretical value of zero. In addition,
the total mass of the organic compounds of each aqueous solution could be predicted, pointing
out that the sensors measured mainly the global contents of the vapor phases. The satisfactory
quantitative results allowed to conclude that the Enose could be a useful tool for the analysis of
volatiles from aqueous solutions containing organic compounds for which Henry’s law is applicable.
The authors are grateful to the Foundation for Science and Technology (FCT,
Portugal) and FED-ER under Programme PT2020 for financial support by national funds FCT/MCTES
to CIMO (UID/AGR/00690/2019) and SusTEC (LA/P/0007/2020)
