Comparison of Sampling Systems for Biological Sample Dehumidification Prior to Electronic Nose Analysis

first_pagesettingsOrder Article Reprints This is an early access version, the complete PDF, HTML, and XML versions will be available soon. Open AccessArticle Comparison of Sampling Systems for Biological Sample Dehumidification Prior to Electronic Nose Analysis by Ana Maria Tischer 1,*ORCID,Beatrice Julia Lotesoriere 1ORCID,Stefano Robbiani 2ORCID,Hamid Navid 1,Emanuele Zanni 2ORCID,Carmen Bax 1ORCID,Fabio Grizzi 3ORCID,Gianluigi Taverna 4,Raffaele Dellacà 2ORCID andLaura Capelli 1ORCID 1 Department of Chemistry, Materials, and Chemical Engineering Giulio Natta, Politecnico di Milano, 20133 Milan, Italy 2 Department of Electronics, Information, and Bioengineering, Politecnico di Milano, 20133 Milan, Italy 3 Department of Immunology and Inflammation, IRCCS Humanitas Research Hospital, 20089 Rozzano, Italy 4 Department of Urology, Humanitas Mater Domini, 21100 Castellanza, Italy * Author to whom correspondence should be addressed. Appl. Sci. 2026, 16(9), 4174; https://doi.org/10.3390/app16094174 (registering DOI) Submission received: 11 March 2026 / Revised: 17 April 2026 / Accepted: 21 April 2026 / Published: 24 April 2026 (This article belongs to the Special Issue State of the Art in Gas Sensing Technology) Downloadkeyboard_arrow_down Browse Figure Versions Notes Abstract It is well known that gas sensor responses are affected by the presence of humidity in the analyzed gas. This is particularly true when dealing with biological fluid samples, whose high moisture content interferes with the adsorption of the trace volatile organic compounds (VOCs) on the sensors’ active layer. To address this challenge, this study focuses on designing and testing a novel sampling system for the dehumidification of biological fluid headspace to be characterized by an electronic nose (e-Nose). Such a system, based on the use of disposable polymeric sampling bags purged with dry air, exploits the polymers’ permeability to water vapor to reduce sample humidity. Tested materials included NalophanTM (20 μm), high-density polyethylene (HDPE, 8, 9, 10 and 11 μm), low-density polyethylene (LDPE, 12 and 50 μm), and biodegradable polyester (Bio-PS, 15 μm). First, dehumidification performance was characterized as a function of dry air flow rate and film type. A purge of 1 L/min accelerated the sample humidity removal compared to passive storage of bags from >2 h to <1 h (from 80% to 20% RH). Second, a mass-balance model was applied to dedicated experiments to decouple water losses due to diffusion and adsorption, showing that diffusion through the polymer wall dominates, while adsorption occurs in the early stages of conditioning. Third, because these materials are not selectively permeable to water, potential loss of water-soluble VOCs during dehumidification was investigated. Pooled urine headspace samples—both raw and spiked with a metabolite mix of VOCs—were dried using each material and analyzed using a photo-ionization detector (PID) and an e-Nose. Results were compared against a NafionTM dryer. Comparison was based on the e-Nose’s ability to discriminate between pooled vs. spiked samples and reveal real-life metabolomic changes. NalophanTM bags and NafionTM dryer provided the highest VOC fingerprint to support discrimination by the e-Nose, while Bio-PS provided the fastest sample dehumidification. The proposed bag-based system offers a cost-effective, disposable, and contamination-free solution to humidity interference in e-Noses.