Methods of assaying a breath sample from a subject for the presence of one or more PFAS are provided. Embodiments of the methods further include providing a composite score that can be used to determine if the subject has been exposed to PFAS and to monitor changes in PFAS exposure over time in the subject. In certain embodiments, a machine learning model may be used to determine if a subject has been exposed to one or more PFAS. The machine learning model may be trained by: analyzing breath samples from a plurality of subjects with a secondary electrospray ionization-high-resolution mass spectrometry analyzer to generate breath assay data; obtaining PFAS exposure data for each subject; training a machine learning model to identify a relationship between the breath samples and PFAS exposure using the breath assay data and the obtained PFAS exposure data; and applying the trained machine learning model to breath assay data, different from the breath assay data used to train the model, to generate a composite score regarding the PFAS exposure for a subject or subjects. In some embodiments, a health evaluation is generated for the subject using the composite score. Also provided are systems for use in practicing methods of the invention.

Methods and sensors for the detection, identification, and quantification of one or more gas species, including volatile organic compounds, in a test sample are described. Methods employ gas sensors comprising a diffusion matrix present on the sensor surface. A gas analyte in a test sample diffuses through the matrix and is detected upon interaction of the analyte with the sensor. A response profile of a gas sensor to a gas analyte in the test sample is compared to a control gas sensor response profile determined in a similar manner for a known gas species. Comparisons of test sample and control sample sensor response profiles enable detection, identification, and quantification of a gas species analyte in a test sample.

VOCs in exhaled breath can be used to diagnose stage 1 lung cancer (SL1C). Three potential biomarkers Acetoin, Dodecane, and p-Cymene have predictive power for SL1C. Acetoin and Dodecane are predictive with relation to their concentrations in the 1 L breath sample, and p-Cymene is predictive 5 with relation to being above or below the limit of detection. The diagnostic of the present invention is capable of detecting S1LC noninvasively and in some cases earlier than other methodologies. This diagnostic can then be paired with appropriate treatments to address S1LC before it grows or metastasizes.

Techniques for determining a volume of exhaled CO.sub.2 as a function of time using side-stream capnography, including obtaining flow dynamics measurements of a subject from a flow sensor; obtaining CO.sub.2 concentration measurements of the subject from a side-stream CO.sub.2 monitor; determining a duration of time (?T.sub.sl) for a sample of gas to flow from a reference point to the side-stream CO.sub.2 monitor; synchronizing in time the CO.sub.2 concentration measurement with the flow dynamics measurement, based on the determined ?T.sub.sl; and determining a volume of CO.sub.2 exhaled as a function of time, based on the flow dynamics measurement and the synchronized CO.sub.2 concentration measurement.

Methods and devices are provided for analyzing acetone in breath. One such method comprises disposing a reactant in a reaction zone within the breath analysis device, wherein the reactant comprises a primary amine disposed on a surface, and wherein the reaction zone has an optical characteristic that is at a reference level. It also comprises pre-storing a liquid nitroprusside solution within the breath analysis device separately from the reactant. The method further comprises using the breath analysis device to cause the breath to contact the reactant in the reaction zone so that the acetone in the breath reacts with the reactant to form a reaction product and, after the reaction product has been formed, using the breath analysis device to cause the nitroprusside solution to contact and react with the reaction product and to facilitate a change in the optical characteristic of the reaction zone relative to the reference level. The method also comprises using the breath analysis device to detect the change in the optical characteristic to sense the acetone in the breath. Apparatuses that use these methods are also described.

A gas sensor element includes a main body having a solid electrolyte body on which a measurement gas-side electrode and a reference gas-side electrode are provided, a trap layer covering an outer peripheral surface of the main body to trap poisoning substances contained in a measurement gas, and a waterproof protective layer covering an outer peripheral surface of the trap layer. In the protective layer, there is formed at least one measurement gas introduction port for introducing the measurement gas to the measurement gas-side electrode via the trap layer.

An electrochromic device comprising a substrate, a set of electrodes disposed on or within the substrate, and a layer comprising ?-WO.sub.3 disposed in electrical communication with the set of electrodes, wherein the layer of ?-WO.sub.3 exhibits polarization switching are described. Methods of making and using the electrochromic devices are also described. The electrochromic devices are used for detecting acetone in a fluid. The observed change in color of the ?-WO.sub.3 layer can be correlated with a subject's medical condition, such as diabetes.

A portable method and sampling device for collecting aerosols comprising biomarkers from exhaled breath of a subject for further sensor based analysis. The sampling device (41) comprising a housing (406) comprising at least one inlet (407) and at least one outlet (408) for the exhaled breath to exit through, and a sampling membrane arranged in the housing. The sampling membrane is arranged to collect the aerosols from said exhaled breath.

Functionalized nanotube arrays, sensors, and related methods of detecting target compounds are presented. A functionalized nanotube array can include a plurality of metal oxide nanotubes. The metal oxide nanotubes can be formed of a metal oxide and can have an interior or exterior surface that is optionally functionalized with at least one metal ion. These metal nanotubes can be used in a sensor for detecting target compounds such as volatile organic compounds, and biomarkers in a fluid environment. The sensor can further include a power source configured to apply a voltage to the nanotube array and a current sensor configured to monitor and detect changes in a response current which varies upon binding with the target compounds.

Methods and devices are provided for analyzing acetone in breath. One such method comprises disposing a reactant in a reaction zone within the breath analysis device, wherein the reactant comprises a primary amine disposed on a surface, and wherein the reaction zone has an optical characteristic that is at a reference level. It also comprises pre-storing a liquid nitroprusside solution within the breath analysis device separately from the reactant. The method further comprises using the breath analysis device to cause the breath to contact the reactant in the reaction zone so that the acetone in the breath reacts with the reactant to form a reaction product and, after the reaction product has been formed, using the breath analysis device to cause the nitroprusside solution to contact and react with the reaction product and to facilitate a change in the optical characteristic of the reaction zone relative to the reference level. The method also comprises using the breath analysis device to detect the change in the optical characteristic to sense the acetone in the breath. Apparatuses that use these methods are also described.