Sampling and analysis of exhaled breath particles
With every breath the human lung emits droplets originating from the Lung-Lining-Fluid. Their analysis requires collection and enrichment in/on suitable media. Current methods are cryogenic condensate sampling, filtration, or by commercial multistage impactors. Because small amounts of analytes are incorporated in large matrices, i.e. the condensed water vapor, the filter material and several impaction foils biochemical analysis is impeded. Therefore, a new technique was developed for localized sampling and enrichment of the droplets directly on an analytical membrane minimizing/avoiding sample preparation. Using a single stage slit-impactor exhaled droplets larger than 0.2 lm impacted in a narrow 120 lm strip on a membrane suitable for immunodetection. For 6 subjects breath aerosols were collected and analysed for different proteins (albumin, SP-D, alpha-1-antitrypsin). Parallel to droplet sampling their total mass was determined using an optical particle counter allowing for standardization of the biochemical results. Immunodetection of the samples confirmed the localized collection of breath particles. For all subjects, there was a good correlation between optical density and the particle mass collected. with high reproducibility. Total mass for a 10-minute sampling period could be as small as about 3 ng. Particle collection by impaction in combination with measurement of physical aerosol properties is a promising technique for breath particle characterization. It provides highly concentrated microsamples from Lung Lining Fluid for consecutive biochemical analysis. Importantly, this sampling method delivering a localized, one-dimensional sample on a narrow strip bears the potential to be adjusted to other methods for analysis, especially those based on phoretic and chromatographic techniques.