Stability assessment of diagnostic parameters for differentiation of oncological status based on gas profile

Long-term stability of sensor arrays remains a major limitation for the practical implementation of electronic nose systems in non-invasive analysis of volatile organic compounds (VOCs) and differentiation of oncological status. Changes in the physicochemical properties of sensing layers during prolonged operation may alter diagnostic parameters and compromise classification consistency. This study evaluated the long-term stability of diagnostically significant parameters obtained from skin gas-profile analysis using a quantum dot-based electronic nose. An eight-sensor piezoelectric electronic nose array based on cadmium sulfide quantum dots with various modifiers was used for skin gas-profile analysis of volunteers and cancer patients. Pair sensitivity parameters (Ai/j) and kinetic sorption parameters derived from chronofrequency responses were assessed by comparing measurements obtained during the pilot study and after two years of sensor operation. Pair sensitivity parameters demonstrated substantial susceptibility to long-term surface degradation and environmental variability, particularly humidity, resulting in pronounced classification drift. In contrast, kinetic sorption parameters exhibited higher temporal stability and lower sensitivity to operating conditions. A correction strategy based on systematic changes in kinetic parameters was developed and applied to compensate for sensor aging effects. The proposed approach reduced classification drift. These findings indicate that correction of long-term sensor drift may help extend the operational lifetime of quantum dot-based electronic nose systems, while kinetic parameters may provide more stable analytical indicators for gas-profile analysis.