Sensors 2026 , 26 , 2049
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Concerning mixed papers from Slovakia and Poland, both contained acetic acid and nonanal, although the values obtained were very low compared with those of other samples. From these profiles, no conclusions could be drawn because the wood type is unknown and the country of origin has not been confirmed. Papers from France (samples P2 and P19) exhibited a similar volatile profile to that of Portuguese papers also produced from E. globulus trees. However, looking at the profiles displayed in Figure 4, obtained with the PDMS fiber, papers from France (P2 and P19) could be distinguished as dodecanal was detected on no other samples.
Figure 4. Radial plots of PDMS-GC-TOF-MS main compounds (excluding dodecanoic acid 1- methylethyl ester as it would overwhelm the graphs due to its much higher peak area) for comparison between French papers and papers from other origins. In summary, SPME-GC-TOF-MS results allowed the identification of the country of origin of paper samples. 3-Hydroxybutanone (acetoin) was identified as a marker for papers produced only in Spain, and dodecanal for papers produced in France. In addition, “Spain and France profiles”, an “India profile” and an “Italy profile” were also identified.
3.3. SPME/E-Nose Analysis 3.3.1. Sensors Coatings
Table 4 shows the frequency decrease in the piezoelectric quartz crystals due to coating. The coatings were selected with the understanding that they must physically adsorb the volatile compounds reported to be responsible for the paper aroma. The interaction between the sensor coating and the volatile compounds must not involve covalent bonds, as such interactions would preclude sensor reversibility. Selectivity is not an issue in electronic noses, but different sensitivities to the target compounds among the sensors are required.
Table4. Frequency decreases due to coating (kHz) for the six piezoelectric quartz crystals used on the sensor array.
Coatings
Frequency Decreases Due to Coating (kHz)
PVP
63 69 25 35 68 58
Mn-Pht THEED
POM
Mn(TPFPP)Cl
Nafion
https://doi.org/10.3390/s26072049
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